2 Oracle Text Indexing Elements
Oracle provides indexing types for storage, filtering, and lexers, and preferences and stoplists that you can use to create an Oracle Text index.
2.1 Overview
When you use the CREATE INDEX statement to create an index or the ALTER INDEX statement to manage an index, you can optionally specify indexing preferences, stoplists, and section groups in the parameter string. Specifying a preference, stoplist, or section group answers one of the following questions about the way Oracle Text indexes text:
Preference Class | Answers the Question |
---|---|
Datastore |
How are your documents stored? |
Filter |
How can the documents be converted to plain text? |
Lexer |
What language is being indexed? |
Wordlist |
How should stem and fuzzy queries be expanded? |
Storage |
How should the index tables be stored? |
Stop List |
What words or themes are not to be indexed? |
Section Group |
Is querying within sections enabled, and how are the document sections defined? |
This chapter describes how to set each preference. Enable an option by creating a preference with one of the types described in this chapter.
2.2 Creating Preferences
To create a datastore, lexer, filter, classifier, wordlist, or storage preference, use the CTX_DDL.CREATE_PREFERENCE procedure and specify one of the types described in this chapter. For some types, you can also set attributes with the CTX_DDL.SET_ATTRIBUTE procedure.
An indexing type names a class of indexing objects that you can use to create an index preference. A type, therefore, is an abstract ID, while a preference is an entity that corresponds to a type. Many system-defined preferences have the same name as types (for example, BASIC_LEXER
), but exact correspondence is not guaranteed. Be careful in assuming the existence or nature of either indexing types or system preferences.
You specify indexing preferences with the CREATE
INDEX
and ALTER
INDEX
statements. Indexing preferences determine how your index is created. For example, lexer preferences indicate the language of the text to be indexed. You can create and specify your own user-defined preferences, or you can use system-defined preferences.
To create a stoplist, use the CTX_DDL.CREATE_STOPLIST procedure. Add stopwords to a stoplist with CTX_DDL.ADD_STOPWORD
.
To create section groups, use CTX_DDL.CREATE_SECTION_GROUP and specify a section group type. Add sections to section groups with the CTX_DDL.ADD_ZONE_SECTION
or CTX_DDL.ADD_FIELD_SECTION
procedures.
2.3 Datastore Types
Use the datastore types to create a datastore preference. This helps you specify how your text is stored.
Table 2-1 Datastore Types
Datastore Type | Use When |
---|---|
Data is stored internally in the text column. Each row is indexed as a single document. |
|
Data is stored in a text table in more than one column. Columns are concatenated to create a virtual document, one for each row. |
|
Data is stored internally in the text column. Document consists of one or more rows stored in a text column in a detail table, with header information stored in the primary table. |
|
Data is stored externally in operating system files. File names are stored in the text column, one for each row. Note: Starting with Oracle Database 19c, the Oracle Text typeFILE_DATASTORE is deprecated. Use
DIRECTORY_DATASTORE instead. |
|
Data is stored in Oracle directory objects. File names are stored in the text column, one for each row. |
|
Data is stored in a nested table. |
|
Data is stored externally in files located on an intranet or the Internet. Uniform Resource Locators (URLs) are stored in the text column. Note: Starting with Oracle Database 19c, the Oracle Text typeURL_DATASTORE is deprecated. Use
NETWORK_DATASTORE instead. |
|
Data is stored externally in files located on an intranet or the Internet. Uniform Resource Locators (URLs) are stored in the text column. |
|
Documents are synthesized at index time by a user-defined stored procedure. |
2.3.1 DIRECT_DATASTORE
Use the DIRECT_DATASTORE
type for text stored directly in the text column, one document for each row. The DIRECT_DATASTORE
type has no attributes.
The following column types are supported: CHAR
, VARCHAR
, VARCHAR2
, BLOB
, CLOB
, BFILE
, XMLType
, and URIType
.
Note:
If your column is a BFILE
, then the index owner must have read permission on all directories used by the BFILEs
.
The following example creates a table with a CLOB
column to store text data. It then populates two rows with text data and indexes the table using the system-defined preference CTXSYS.DEFAULT_DATASTORE
.
create table mytable(id number primary key, docs clob); insert into mytable values(111555,'this text will be indexed'); insert into mytable values(111556,'this is a direct_datastore example'); commit; create index myindex on mytable(docs) indextype is ctxsys.context parameters ('DATASTORE CTXSYS.DEFAULT_DATASTORE');
2.3.2 MULTI_COLUMN_DATASTORE
Use the MULTI_COLUMN_DATASTORE
datastore when your text is stored in more than one column. During indexing, the system concatenates the text columns, tags the column text, and indexes the text as a single document. The XML-like tagging is optional. You can also set the system to filter and concatenate binary columns.
2.3.2.1 MULTI_COLUMN_DATASTORE Attributes
The data store MULTI_COLUMN_DATASTORE
has the attributes shown in Table 2-2.
Table 2-2 MULTI_COLUMN_DATASTORE Attributes
2.3.2.2 Indexing and DML
To index, you must create a dummy column to specify in the CREATE
INDEX
statement. This column's contents are not made part of the virtual document, unless its name is specified in the columns attribute.
The index is synchronized only when the dummy column is updated. You can create triggers to propagate changes if needed.
2.3.2.3 MULTI_COLUMN_DATASTORE Restriction
You cannot create a multicolumn datastore with XMLType
columns. MULTI_COLUMN_DATA_STORE
does not support XMLType
. You can create a CONTEXT
index with an XMLType
column, as described in Oracle Text SQL Statements and Operators .
2.3.2.4 MULTI_COLUMN_DATASTORE Example
The following example creates a multicolumn datastore preference called my_multi
with three text columns:
begin
ctx_ddl.create_preference('my_multi', 'MULTI_COLUMN_DATASTORE'); ctx_ddl.set_attribute('my_multi', 'columns', 'column1, column2, column3');
end;
2.3.2.5 MULTI_COLUMN_DATASTORE Filter Example
The following example creates a multicolumn datastore preference and denotes that the bar
column is to be filtered with the AUTO_FILTER
.
ctx_ddl.create_preference('MY_MULTI','MULTI_COLUMN_DATASTORE'); ctx_ddl.set_attribute('MY_MULTI', 'COLUMNS','foo,bar'); ctx_ddl.set_attribute('MY_MULTI','FILTER','N,Y');
The multicolumn datastore fetches the content of the foo
and bar
columns, filters bar
, then composes the compound document as:
<FOO> foo contents </FOO> <BAR> bar filtered contents (probably originally HTML) </BAR>
The N flags do not need not be specified, and there does not need to be a flag for every column. Only the Y flags must be specified, with commas to denote which column they apply to. For example:
ctx_ddl.create_preference('MY_MULTI','MULTI_COLUMN_DATASTORE'); ctx_ddl.set_attribute('MY_MULTI', 'COLUMNS','foo,bar,zoo,jar'); ctx_ddl.set_attribute('MY_MULTI','FILTER',',,Y');
This example filters only the column zoo
.
2.3.2.6 Tagging Behavior
During indexing, the system creates a virtual document for each row. The virtual document is composed of the contents of the columns concatenated in the listing order with column name tags automatically added.
For example:
create table mc(id number primary key, name varchar2(10), address varchar2(80)); insert into mc values(1, 'John Smith', '123 Main Street'); exec ctx_ddl.create_preference('mymds', 'MULTI_COLUMN_DATASTORE'); exec ctx_ddl.set_attibute('mymds', 'columns', 'name, address');
This produces the following virtual text for indexing:
<NAME> John Smith </NAME> <ADDRESS> 123 Main Street </ADDRESS>
2.3.2.7 Indexing Columns as Sections
To index tags as sections, you can optionally create field sections with BASIC_SECTION_GROUP
.
Note:
No section group is created when you use the MULTI_COLUMN_DATASTORE
. To create sections for these tags, you must create a section group.
When you use expressions or functions, the tag is composed of the first 30 characters of the expression unless a column alias is used.
For example, if your expression is as follows:
exec ctx_ddl.set_attibute('mymds', 'columns', '4 + 17');
then it produces the following virtual text:
<4 + 17> 21 </4 + 17>
If your expression is as follows:
exec ctx_ddl.set_attibute('mymds', 'columns', '4 + 17 col1');
then it produces the following virtual text:
<col1> 21 <col1>
The tags are in uppercase unless the column name or column alias is in lowercase and surrounded by double quotation marks. For example:
exec ctx_ddl.set_attibute('mymds', 'COLUMNS', 'foo');
This produces the following virtual text:
<FOO> content of foo </FOO>
For lowercase tags, use the following:
exec ctx_ddl.set_attibute('mymds', 'COLUMNS', 'foo "foo"');
This expression produces:
<foo> content of foo </foo>
2.3.3 DETAIL_DATASTORE
Use the DETAIL_DATASTORE
type for text stored directly in the database in detail tables, with the indexed text column located in the primary table.
2.3.3.1 DETAIL_DATASTORE Attributes
The DETAIL_DATASTORE
type has the attributes described in Table 2-3.
Table 2-3 DETAIL_DATASTORE Attributes
Attribute | Attribute Value |
---|---|
binary |
Specify Specify |
detail_table |
Specify the name of the detail table ( |
detail_key |
Specify the name of the detail table foreign key column. |
detail_lineno |
Specify the name of the detail table sequence column. |
detail_text |
Specify the name of the detail table text column. |
2.3.3.2 Synchronizing Primary/Detail Indexes
Changes to the detail table do not trigger re-indexing when you synchronize the index. Only changes to the indexed column in the primary table triggers a re-index when you synchronize the index.
You can create triggers on the detail table to propagate changes to the indexed column in the primary table row.
2.3.3.3 Example Primary/Detail Tables
This example illustrates how primary and detail tables are related to each other.
2.3.3.3.1 Primary Table Example
Primary tables define the documents in a primary/detail relationship. Assign an identifying number to each document. The following table is an example primary table, called my_primary
:
Column Name | Column Type | Description |
---|---|---|
|
|
Document ID, unique for each document (primary key) |
|
|
Author of document |
|
|
Title of document |
|
|
Dummy column to specify in |
Note:
Your primary table must include a primary key column when you use the DETAIL_DATASTORE
type.
2.3.3.3.2 Detail Table Example
Detail tables contain the text for a document, whose content is usually stored across a number of rows.
The following detail table my_detail
is related to the primary table my_primary
with the article_id
column. This column identifies the primary document to which each detail row (sub-document) belongs.
Column Name | Column Type | Description |
---|---|---|
|
|
Document ID that relates to primary table |
|
|
Sequence of document in the primary document defined by |
|
|
Document text |
2.3.3.3.3 Detail Table Example Attributes
In this example, the DETAIL_DATASTORE
attributes have the following values:
Attribute | Attribute Value |
---|---|
|
|
|
|
|
|
|
|
|
|
Use CTX_DDL.CREATE_PREFERENCE to create a preference with DETAIL_DATASTORE
. Use CTX_DDL.SET_ATTRIBUTE to set the attributes for this preference as described earlier. The following example shows how this is done:
begin
ctx_ddl.create_preference('my_detail_pref', 'DETAIL_DATASTORE'); ctx_ddl.set_attribute('my_detail_pref', 'binary', 'true'); ctx_ddl.set_attribute('my_detail_pref', 'detail_table', 'my_detail'); ctx_ddl.set_attribute('my_detail_pref', 'detail_key', 'article_id'); ctx_ddl.set_attribute('my_detail_pref', 'detail_lineno', 'seq'); ctx_ddl.set_attribute('my_detail_pref', 'detail_text', 'text');
end;
2.3.3.3.4 Primary/Detail Index Example
To index the document defined in this primary/detail relationship, specify a column in the primary table using the CREATE INDEX
statement.
The column you specify must be one of the allowed types.
This example uses the body
column, whose function is to enable the creation of the primary/detail index and to improve readability of the code. The my_detail_pref
preference is set to DETAIL_DATASTORE
with the required attributes:
CREATE INDEX myindex on my_primary(body) indextype is ctxsys.context parameters('datastore my_detail_pref');
In this example, you can also specify the title
or author
column to create the index. However, if you do so, changes to these columns will trigger a re-index operation.
2.3.4 FILE_DATASTORE
The FILE_DATASTORE
type is used for text stored in files accessed through the local file system.
Note:
Starting with Oracle Database 19c, the Oracle Text type
FILE_DATASTORE
is deprecated. Use
DIRECTORY_DATASTORE
instead.
Oracle
recommends that you replace FILE_DATASTORE
text indexes with the
DIRECTORY_DATASTORE
index type, which is available starting
with Oracle Database 19c. DIRECTORY_DATASTORE
provides greater
security because it enables file access to be based on directory objects.
Note:
-
The
FILE_DATASTORE
type may not work with certain types of remote-mounted file systems. -
The character set of the file datastore is assumed to be the character set of the database.
2.3.4.1 FILE_DATASTORE Attributes
The FILE_DATASTORE
type has the attributes described Table 2-4.
Table 2-4 FILE_DATASTORE Attributes
Attribute | Attribute Value |
---|---|
|
path1:path2:pathn |
|
name |
- path
-
Specifies the full directory path name of the files stored externally in a file system. When you specify the full directory path as such, you need to include only file names in your text column.
You can specify multiple paths for the
path
attribute, with each path separated by a colon (:) on UNIX and semicolon(;) on Windows. File names are stored in the text column in the text table.If you do not specify a path for external files with this attribute, then Oracle Text requires that the path be included in the file names stored in the text column.
The
PATH
attribute has the following limitations:-
If you specify a
PATH
attribute, then you can only use a simple file name in the indexed column. You cannot combine thePATH
attribute with a path as part of the file name. If the files exist in multiple folders or directories, you must leave thePATH
attribute unset, and include the full file name, withPATH
, in the indexed column. -
On Windows systems, the files must be located on a local drive. They cannot be on a remote drive, whether the remote drive is mapped to a local drive letter.
-
- filename_charset
-
Specifies a valid Oracle character set name (maximum length 30 characters) to be used by the file datastore for converting file names. In general, the Oracle database can use a different character set than the operating system. This can lead to problems in finding files (which may raise DRG-11513 errors) when the indexed column contains characters that are not convertible to the operating system character set. By default, the file datastore will convert the file name to WE8ISO8859p1 for ASCII platforms or WE8EBCDIC1047 for EBCDIC platforms.
However, this may not be sufficient for applications with multibyte character sets for both the database and the operating system, because neither WE8ISO8859p1 nor WE8EBCDIC1047 supports multibyte characters. The attribute
filename_charset
rectifies this problem. If specified, then the datastore will convert from the database character set to the specified character set rather than to ISO8859 or EBCDIC.If the
filename_charset
attribute is the same as the database character set, then the file name is used as is. Iffilename_charset
is not a valid character set, then the error "DRG-10763: value %s is not a valid character set" is raised.
2.3.4.2 FILE_DATASTORE and Security
File and URL datastores enable access to files on the actual database disk. This may be undesirable when security is an issue since any user can browse the file system that is accessible to the Oracle user. Any user attempting to create an index using FILE
or URL
datastores must have the TEXT DATASTORE ACCESS
system privilege granted to the user directly, or the index creation will fail. Granting the user TEXT DATASTORE ACCESS
privilege indirectly by granting it to the user’s role does not work and the index creation will still fail. Thus, by default, users are not able to create indexes that use the FILE
or URL
datastores. Granting TEXT DATASTORE ACCESS
to PUBLIC
gives any user the privilege to index either an arbitrary file in the file system in the case of FILE
datastore and an arbitrary URL in the case of URL
datastore and is not recommended.
For example, the following statement grants TEXT DATASTORE ACCESS
to the user SCOTT:
grant TEXT DATASTORE ACCESS to SCOTT;
The CREATE INDEX operation will fail when a user that does not have TEXT DATASTORE ACCESS
privilege tries to create an index on a FILE
or URL
datastore. For example:
CREATE INDEX myindex ON mydocument(TEXT) INDEXTYPE IS ctxsys.context PARAMETERS('DATASTORE ctxsys.file_datastore')
In this case, if the user does not have the TEXT DATASTORE ACCESS
privilege granted directly to it, then index creation will fail and returns an error. For users who have the TEXT DATASTORE ACCESS
privilege, the index creation will proceed normally.
The user’s privilege is checked any time the datastore is accessed. This includes index creation, index sync, and calls to document services, such as CTX_DOC.HIGHLIGHT
.
2.3.4.3 FILE_DATASTORE Example
This example creates a file datastore preference called COMMON_DIR
that has a path of /mydocs
:
begin ctx_ddl.create_preference('COMMON_DIR','FILE_DATASTORE'); ctx_ddl.set_attribute('COMMON_DIR','PATH','/mydocs'); end;
When you populate the table mytable
, you need only insert file names. The path attribute tells the system where to look during the indexing operation.
create table mytable(id number primary key, docs varchar2(2000)); insert into mytable values(111555,'first.txt'); insert into mytable values(111556,'second.txt'); commit;
Create the index as follows:
create index myindex on mytable(docs) indextype is ctxsys.context parameters ('datastore COMMON_DIR');
2.3.5 DIRECTORY_DATASTORE
Use the DIRECTORY_DATASTORE
type during indexing to access the text stored in files which can be accessed through Oracle directory objects.
Starting with Oracle Database 19c, the Oracle Text type
FILE_DATASTORE
is deprecated. Use
DIRECTORY_DATASTORE
instead.
Oracle
recommends that you replace FILE_DATASTORE
text indexes with the
DIRECTORY_DATASTORE
index type, which is available starting
with Oracle Database 19c. DIRECTORY_DATASTORE
provides greater
security because it enables file access to be based on directory objects.
A directory object specifies an alias for a directory on the server file system where external binary file LOBs (BFILE
s) and external table data are located. When you use DIRECTORY_DATASTORE
type, another PDB user can not access directory objects in your PDB without read access to the directory objects.
DIRECTORY_DATASTORE
type to use an Oracle directory object as an attribute for the CTX_DDL.SET_ATTRIBUTE
procedure. You must have read access to the Oracle directory object to access the files stored within the directory. If you have access, then during index creation, you can use the path stored in the Oracle directory object to access the files stored in the file system.
Note:
-
To create an Oracle directory object, you must have the
CREATE ANY DIRECTORY
privilege. Typically, a system administrator user creates the directory and provides read access to the directory for an Oracle Text user. -
DIRECTORY_DATASTORE
can be used with a context index onCHAR
datatype column only if the file name fills the column.
2.3.5.1 DIRECTORY_DATASTORE Attributes
DIRECTORY_DATASTORE
has the following attributes:
Table 2-5 DIRECTORY_DATASTORE Attributes
Attribute | Attribute Values |
---|---|
|
Specify the name of the directory object where the data to be indexed is stored. The default is If you have access to the Oracle directory object, then you can also access the files in its sub-directories. |
|
Specify a valid Oracle character set name (maximum length 30 characters) to be used by the directory datastore for converting file names. In general, the Oracle database can use a different character set than the operating system. This can lead to problems in finding files (which may raise DRG-11513 errors) when the indexed column contains characters that are not convertible to the operating system character set. By default, the directory datastore will convert the file name to WE8ISO8859p1 for ASCII platforms or WE8EBCDIC1047 for EBCDIC platforms. However, this may not be sufficient for applications with multibyte character sets for both the database and the operating system, because neither WE8ISO8859p1 nor WE8EBCDIC1047 supports multibyte characters. The attribute If the |
2.3.5.2 DIRECTORY_DATASTORE Example
This example shows you how to create an index with DIRECTORY_DATASTORE
type by securely accessing files under an Oracle directory object.
Create an Oracle directory object to store the path of the files. You must have the CREATE ANY DIRECTORY
privilege to create an Oracle directory object.
create directory myhome as 'directory_path';
Create a directory datastore preference called MYDS
and set the directory attribute with myhome,
which is the Oracle directory object:
exec ctx_ddl.create_preference('MYDS','DIRECTORY_DATASTORE')
exec ctx_ddl.set_attribute('MYDS','DIRECTORY','myhome')
Create a table named mytable
and populate it with file names only. The directory attribute tells the system where to look during the indexing operation.
create table mytable(id number primary key, docs varchar2(2000));
insert into mytable values(111555,'first.txt');
insert into mytable values(111556,'second.txt');
Create the index as follows:
create index myindex on mytable(docs)
indextype is ctxsys.context
parameters ('datastore MYDS');
2.3.6 URL_DATASTORE
Use the URL_DATASTORE
type for text stored in files on the World Wide Web (accessed through HTTP or FTP) and local file system (accessed through the file protocol).
Store each URL in a single text field.
Note:
Starting with Oracle Database 19c, the Oracle Text type
URL_DATASTORE
is deprecated. Use
NETWORK_DATASTORE
instead.
The
URL_DATASTORE
type is used for text stored in files on the
internet (accessed through HTTP or FTP), and for text stored in local file system
files (accessed through the file protocol). It is replaced with
NETWORK_DATASTORE
, which uses ACLs to allow access to specific
servers. This change aligns Oracle Text more closely with the standard operating and
security model for accessing URLs from the database.
2.3.6.1 URL_DATASTORE URL Syntax
The syntax of a URL you store in a text field is as follows (with brackets indicating optional parameters):
[URL:]<access_scheme>://<host_name>[:<port_number>]/[<url_path>]
The access_scheme
string can be either ftp, http, or file. For example:
http://mycomputer.us.example.com/home.html
Note:
The login:password@
syntax within the URL is supported only for the ftp access scheme.
Because this syntax is partially compliant with the RFC 1738 specification, the following restriction holds for the URL syntax: The URL must contain only printable ASCII characters. Non-printable ASCII characters and multibyte characters must be escaped with the %xx notation, where xx is the hexadecimal representation of the special character.
2.3.6.2 URL_DATASTORE Attributes
URL_DATASTORE
has the following attributes:
Table 2-6 URL_DATASTORE Attributes
Attribute | Attribute Value |
---|---|
|
The value of this attribute is ignored. This is provided for backward compatibility. |
|
The value of this attribute is ignored. |
|
The value of this attribute is ignored. This is provided for backward compatibility. |
|
The value of this attribute is ignored. This is provided for backward compatibility. |
|
The value of this attribute is ignored. This is provided for backward compatibility. |
|
Specify the host name of http proxy server. Optionally specify port number with a colon in the form |
|
Specify the host name of ftp proxy server. Optionally specify port number with a colon in the form |
|
Specify the domain for no proxy server. Use a comma-delimited string of up to 16 domain names. |
- timeout
-
The value of this attribute is ignored. This is provided for backward compatibility.
- maxthreads
-
The value of this attribute is ignored.
URL_DATASTORE
is single-threaded. This is provided for backward compatibility. - urlsize
-
The value of this attribute is ignored. This is provided for backward compatibility.
- maxdocsize
-
The value of this attribute is ignored. This is provided for backward compatibility.
- maxurls
-
The value of this attribute is ignored. This is provided for backward compatibility.
- http_proxy
-
Specify the fully qualified name of the host computer that serves as the HTTP proxy (gateway) for the computer on which Oracle Text is installed. You can optionally specify port number with a colon in the form
hostname:port
.You must set this attribute if the computer is in an intranet that requires authentication through a proxy server to access Web files located outside the firewall.
- ftp_proxy
-
Specify the fully qualified name of the host computer that serves as the FTP proxy (gateway) for the server on which Oracle Text is installed. You can optionally specify a port number with a colon in the form
hostname:port
.This attribute must be set if the computer is in an intranet that requires authentication through a proxy server to access Web files located outside the firewall.
- no_proxy
-
Specify a string of domains (up to sixteen, separated by commas) that are found in most, if not all, of the computers in your intranet. When one of the domains is encountered in a host name, no request is sent to the server(s) specified for
ftp_proxy
andhttp_proxy
. Instead, the request is processed directly by the host computer identified in the URL.For example, if the string us.example.com, uk.example.com is entered for
no_proxy
, any URL requests to computers that contain either of these domains in their host names are not processed by your proxy server(s).
2.3.6.3 URL_DATASTORE and Security
For a discussion of how to control file access security for file and URL datastores, refer to "FILE_DATASTORE and Security".
2.3.6.4 URL_DATASTORE Example
This example creates a URL_DATASTORE
preference called URL_PREF
for which the http_proxy
, no_proxy
, and timeout
attributes are set. The defaults are used for the attributes that are not set.
begin ctx_ddl.create_preference('URL_PREF','URL_DATASTORE'); ctx_ddl.set_attribute('URL_PREF','HTTP_PROXY','www-proxy.us.example.com'); ctx_ddl.set_attribute('URL_PREF','NO_PROXY','us.example.com'); ctx_ddl.set_attribute('URL_PREF','Timeout','300'); end;
Create the table and insert values into it:
create table urls(id number primary key, docs varchar2(2000)); insert into urls values(111555,'http://context.us.example.com'); insert into urls values(111556,'http://www.sun.com'); commit;
To create the index, specify URL_PREF
as the datastore:
create index datastores_text on urls ( docs ) indextype is ctxsys.context parameters ( 'Datastore URL_PREF' );
2.3.7 NETWORK_DATASTORE
Use the NETWORK_DATASTORE
type during indexing to access the files stored on the World Wide Web through HTTP and HTTPS.
Starting with Oracle Database 19c, the Oracle Text type
URL_DATASTORE
is deprecated. Use
NETWORK_DATASTORE
instead.
The
URL_DATASTORE
type is used for text stored in files on the
internet (accessed through HTTP or FTP), and for text stored in local file system
files (accessed through the file protocol). It is replaced with
NETWORK_DATASTORE
, which uses ACLs to allow access to specific
servers. This change aligns Oracle Text more closely with the standard operating and
security model for accessing URLs from the database.
When you use NETWORK_DATASTORE
type, you can access a URL after the website certificate is verified in Oracle wallet and ACL package.
FTP and file protocol are not supported in NETWORK_DATASTORE
type. To access the files stored in the local file system, use the DIRECTORY_DATASTORE
type.
During index creation, the URL stored in the datastore is used to access the files stored in the World Wide Web. The access is granted after verifying the website certificate in Oracle wallet.
Note:
NETWORK_DATASTORE
can be used with a context index on CHAR
datatype column only if the file name fills the column.
2.3.7.1 NETWORK_DATASTORE URL Syntax
The syntax of a URL you store in a datastore is as follows (with brackets indicating optional parameters):
[URL:]<access_scheme>://<host_name>[:<port_number>]/[<url_path>]
The access_scheme
string can be either http or https. For example:
https://mycomputer.us.example.com/home.html
Because this syntax is partially compliant with the RFC 1738 specification, the following restriction holds for the URL syntax: The URL must contain only printable ASCII characters. Non-printable ASCII characters and multibyte characters must be escaped with the %xx notation, where xx is the hexadecimal representation of the special character.
2.3.7.2 NETWORK_DATASTORE Attributes
NETWORK_DATASTORE
has the following attributes:
Table 2-7 NETWORK_DATASTORE Attributes
Attribute | Attribute Value |
---|---|
|
Specify the time out value for all future HTTP requests that use the The default value is |
|
Specify the fully qualified name of the host computer that serves as the HTTP proxy (gateway) for the computer on which Oracle Text is installed. You can optionally specify port number with a colon in the form You must set this attribute if the computer is in an intranet that requires authentication through a proxy server to access Web files located outside the firewall. For HTTP network connection, an ACL package is required so that the |
|
Specify the fully qualified name of the host computer that serves as the HTTPS proxy (gateway) for the computer on which Oracle Text is installed. You can optionally specify port number with a colon in the form You must set this attribute if the computer is in an intranet that requires authentication through a proxy server to access Web files located outside the firewall. For HTTPS network connection, in addition to the ACL package, an Oracle wallet is also required. You can create an Oracle wallet using either Oracle Wallet Manager or the To create an Oracle wallet using the
To add a trusted certificate to an Oracle wallet, use the
Use the
|
|
Specify a string of domains (up to sixteen, separated by commas) that are found in most, if not all, of the computers in your intranet. When one of the domains is encountered in a host name, no request is sent to the server(s) specified for For example, if the string us.example.com, uk.example.com is entered for |
See Also:
-
Oracle Database PL/SQL Packages and Types Reference for more information about
DBMS_NETWORK_ACL_ADMIN
package -
Oracle Database PL/SQL Packages and Types Reference for more information about
UTL_HTTP
package -
Oracle Database Enterprise User Security Administrator's Guide for more information about Oracle Wallet Manager
2.3.7.3 NETWORK_DATASTORE Example
This example shows you how to configure HTTP and HTTPS network connections and create an index based on the NETWORK_DATASTORE
type to access the files stored on the World Wide Web.
Create a user and grant the necessary privileges:
CREATE USER myuser IDENTIFIED by password;
GRANT connect, resource, unlimited tablespace, ctxapp to myuser;
Append an access control entry (ACE) to the ACL of a network host. The ACL controls access to the given host from the database and the ACE specifies the privileges granted to or denied from the specified principal. When host
is specified as '*',
you can access any host through the network datastore which uses UTL_HTTP
package internally to access data from websites through HTTP.
begin
DBMS_NETWORK_ACL_ADMIN.APPEND_HOST_ACE(
host => '*',
ace => xs$ace_type(privilege_list => xs$name_list('connect', 'resolve'),
principal_name => 'MYUSER',
principal_type => xs_acl.ptype_db));
end;
/
Create a network datastore preference called NETWORK_PREF:
begin
ctx_ddl.create_preference('NETWORK_PREF','NETWORK_DATASTORE');
ctx_ddl.set_attribute('NETWORK_PREF','HTTP_PROXY','www-proxy.us.example.com');
ctx_ddl.set_attribute('NETWORK_PREF','NO_PROXY','us.example.com');
ctx_ddl.set_attribute('NETWORK_PREF','TIMEOUT','300');
end;
/
Create a table named mytable
and populate it with URLs:
create table mytable(id number primary key, docs varchar2(2000));
insert into mytable values(111555,'http://context.example.com');
insert into mytable values(111556,'http://www.johndoe.com');
Create the index as follows:
create index myindex on mytable(docs)
indextype is ctxsys.context
parameters ('datastore NETWORK_PREF');
See Also:
-
Oracle Database PL/SQL Packages and Types Reference for more information about
DBMS_NETWORK_ACL_ADMIN
package -
Oracle Database PL/SQL Packages and Types Reference for more information about
UTL_HTTP
package
2.3.8 USER_DATASTORE
Use the USER_DATASTORE
type to define stored procedures that synthesize documents during indexing. For example, a user procedure might synthesize author, date, and text columns into one document to have the author and date information be part of the indexed text.
2.3.8.1 USER_DATASTORE Attributes
USER_DATASTORE
has the following attributes:
Table 2-8 USER_DATASTORE Attributes
Attribute | Attribute Value |
---|---|
|
Specify the procedure that synthesizes the document to be indexed. This procedure can be owned by any user and must be executable by the index owner. |
|
Specify the data type of the second argument to procedure. Valid values are When you specify |
- procedure
-
Specify the name of the procedure that synthesizes the document to be indexed. This specification must be in the form
PROCEDURENAME
orPACKAGENAME.PROCEDURENAME
. You can also specify the schema owner name.The procedure you specify must have two arguments defined as follows:
procedure (r IN ROWID, c IN OUT NOCOPY output_type)
The first argument r must be of type
ROWID
. The second argument c must be of the type specified in theoutput_type
attribute.NOCOPY
is a compiler hint that instructs Oracle Text to pass parameter c by reference if possible.Note:
Procedure names should not include the semicolon character.
The stored procedure is called once for each row indexed. Given the rowid of the current row,
procedure
must write the text of the document into its second argument, whose type you specify withoutput_type
.
2.3.8.2 USER_DATASTORE Constraints
The following constraints apply to procedure
:
-
It can be owned by any user, but the user must have database permissions to execute
procedure
correctly -
It must be executable by the index owner
-
It must not enter DDL or transaction control statements, like
COMMIT
2.3.8.3 USER_DATASTORE Editing Procedure after Indexing
When you change or edit the stored procedure, indexes based on it will not be notified, so you must manually re-create such indexes. So if the stored procedure makes use of other columns, and those column values change, the row will not be re-indexed. The row is re-indexed only when the indexed column changes.
2.3.8.4 USER_DATASTORE with CLOB Example
Consider a table in which the author, title, and text fields are separate, as in the articles
table defined as follows:
create table articles( id number, author varchar2(80), title varchar2(120), text clob );
The author and title fields are to be part of the indexed document text. Assume user appowner
writes a stored procedure with the user datastore interface that synthesizes a document from the text, author, and title fields:
create procedure myproc(rid in rowid, tlob in out clob nocopy) is begin for c1 in (select author, title, text from articles where rowid = rid) loop
dbms_lob.writeappend(tlob, length(c1.title), c1.title); dbms_lob.writeappend(tlob, length(c1.author), c1.author); dbms_lob.writeappend(tlob, length(c1.text), c1.text);
end loop; end;
This procedure takes in a rowid and a temporary CLOB
locator, and concatenates all the article's columns into the temporary CLOB
. The for loop executes only once.
The user appowner
creates the preference as follows:
begin
ctx_ddl.create_preference('myud', 'user_datastore'); ctx_ddl.set_attribute('myud', 'procedure', 'myproc'); ctx_ddl.set_attribute('myud', 'output_type', 'CLOB');
end;
When appowner
creates the index on articles(text)
using this preference, the indexing operation sees author and title in the document text.
2.3.8.5 USER_DATASTORE with BLOB_LOC Example
The following procedure might be used with OUTPUT_TYPE
BLOB_LOC
:
procedure myds(rid in rowid, dataout in out nocopy blob) is l_dtype varchar2(10); l_pk number; begin select dtype, pk into l_dtype, l_pk from mytable where rowid = rid; if (l_dtype = 'MOVIE') then select movie_data into dataout from movietab where fk = l_pk; elsif (l_dtype = 'SOUND') then select sound_data into dataout from soundtab where fk = l_pk; end if; end;
The user appowner
creates the preference as follows:
begin
ctx_ddl.create_preference('myud', 'user_datastore'); ctx_ddl.set_attribute('myud', 'procedure', 'myproc'); ctx_ddl.set_attribute('myud', 'output_type', 'blob_loc');
end;
2.3.9 NESTED_DATASTORE
Use the nested datastore type to index documents stored as rows in a nested table.
2.3.9.1 NESTED_DATASTORE Attributes
NESTED_DATASTORE
has the following attributes:
Table 2-9 NESTED_DATASTORE Attributes
Attribute | Attribute Value |
---|---|
Specify the name of the nested table column. This attribute is required. Specify only the column name. Do not specify schema owner or containing table name. |
|
Specify the type of nested table. This attribute is required. You must provide owner name and type. |
|
Specify the name of the attribute in the nested table that orders the lines. This is like |
|
Specify the name of the column in the nested table type that contains the text of the line. This is like |
|
Specify |
When using the nested table datastore, you must index a dummy column, because the extensible indexing framework disallows indexing the nested table column. See "NESTED_DATASTORE Example".
DML on the nested table is not automatically propagated to the dummy column used for indexing. For DML on the nested table to be propagated to the dummy column, your application code or trigger must explicitly update the dummy column.
Filter defaults for the index are based on the type of the nested_text
column.
During validation, Oracle Text checks that the type exists and that the attributes you specify for nested_lineno
and nested_text
exist in the nested table type. Oracle Text does not check that the named nested table column exists in the indexed table.
2.3.9.2 NESTED_DATASTORE Example
This section shows an example of using the NESTED_DATASTORE
type to index documents stored as rows in a nested table.
2.3.9.2.1 Create the Nested Table
The following code creates a nested table and a storage table mytab for the nested table:
create type nt_rec as object ( lno number, -- line number ltxt varchar2(80) -- text of line ); create type nt_tab as table of nt_rec; create table mytab ( id number primary key, -- primary key dummy char(1), -- dummy column for indexing doc nt_tab -- nested table ) nested table doc store as myntab;
2.3.9.2.2 Insert Values into Nested Table
The following code inserts values into the nested table for the parent row with ID equal to 1.
insert into mytab values (1, null, nt_tab()); insert into table(select doc from mytab where id=1) values (1, 'the dog'); insert into table(select doc from mytab where id=1) values (2, 'sat on mat '); commit;
2.3.9.2.3 Create Nested Table Preferences
The following code sets the preferences and attributes for the NESTED_DATASTORE
according to the definitions of the nested table type nt_tab
and the parent table mytab
:
begin -- create nested datastore pref ctx_ddl.create_preference('ntds','nested_datastore'); -- nest tab column in main table ctx_ddl.set_attribute('ntds','nested_column', 'doc'); -- nested table type ctx_ddl.set_attribute('ntds','nested_type', 'scott.nt_tab'); -- lineno column in nested table ctx_ddl.set_attribute('ntds','nested_lineno','lno'); --text column in nested table ctx_ddl.set_attribute('ntds','nested_text', 'ltxt'); end;
2.3.9.2.4 Create Index on Nested Table
The following code creates the index using the nested table datastore:
create index myidx on mytab(dummy) -- index dummy column, not nest table indextype is ctxsys.context parameters ('datastore ntds');
2.4 Filter Types
Use the filter types to create preferences that determine how text is filtered for indexing. Filters enable word processor documents, formatted documents, plain text, HTML, and XML documents to be indexed.
For formatted documents, Oracle Text stores documents in their native format and uses filters to build interim plain text or HTML versions of the documents. Oracle Text indexes the words derived from the plain text or HTML version of the formatted document.
To create a filter preference, you must use one of the filter types shown in Table 2-10.
Table 2-10 Filter Types
Filter | When Used |
---|---|
Auto filter for filtering formatted documents. |
|
No filtering required. Use for indexing plain text, HTML, or XML documents. |
|
Use the |
|
User-defined external filter to be used for custom filtering. |
|
User-defined stored procedure filter to be used for custom filtering. |
2.4.1 AUTO_FILTER
The AUTO_FILTER
is a universal filter that filters most document formats, including PDF and Microsoft Word documents. Use it for indexing both single-format and mixed-format columns. This filter automatically bypasses plain text, HTML, XHTML, SGML, and XML documents.
See Also:
Oracle Text Supported Document Formats, for a list of the formats supported by AUTO_FILTER
, and to learn more about how to set up your environment
Note:
The AUTO_FILTER
replaces the INSO_FILTER
, which has been deprecated. While every effort has been made to ensure maximal backward compatibility between the two filters, so that applications using INSO_FILTER
will continue to work without modification, some differences may arise. Users should therefore use AUTO_FILTER
in their new programs and, when possible, replace instances of INSO_FILTER
, and any system preferences or constants that make use of it, in older applications.
2.4.1.1 AUTO_FILTER Attributes
The AUTO_FILTER
preference has the attributes shown in Table 2-11.
Table 2-11 AUTO_FILTER Attributes
Attribute | Attribute Value |
---|---|
|
Specify the How this wait period is used depends on how you set This feature is disabled for rows for which the corresponding charset and format column cause the Use this feature to prevent the Oracle Text indexing operation from waiting indefinitely on a hanging filter operation. |
|
Specify either Specify Specify |
|
Setting this attribute has no effect on filter performance or filter output. It is maintained for backward compatibility. |
2.4.1.2 AUTO_FILTER and Indexing Formatted Documents
Use AUTO_FILTER
to index a text column containing formatted documents, such as Microsoft Word. This filter automatically detects the document format.
Use the CTXSYS
.AUTO_FILTER
system-defined preference in the parameter clause as follows:
create index hdocsx on hdocs(text) indextype is ctxsys.context parameters ('datastore ctxsys.directory_datastore filter ctxsys.auto_filter');
2.4.1.3 AUTO_FILTER and Explicitly Bypassing Plain Text or HTML in Mixed Format Columns
The AUTO_FILTER
can index mixed-format columns, automatically bypassing plain text, HTML, and XML documents. However, if you prefer not to depend on the built-in bypass mechanism, you can explicitly tag your rows as text and cause the AUTO_FILTER
to ignore the row and not process the document in any way.
A mixed-format column is a text column containing more than one document format, such as a column that contains Microsoft Word, PDF, plain text, and HTML documents.
The format column in the base table enables you to specify the type of document contained in the text column. You can specify the following document types: TEXT
, BINARY
, and IGNORE
. During indexing, the AUTO_FILTER
ignores any document typed TEXT
, assuming the charset column is not specified. The difference between a document with a TEXT
format column type and one with an IGNORE
type is that the TEXT
document is indexed, but ignored by the filter, while the IGNORE
document is not indexed at all. Use IGNORE
to overlook documents such as image files, or documents in a language that you do not want to index. IGNORE
can be used with any filter type.
To set up the AUTO_FILTER
bypass mechanism, you must create a format column in your base table.
For example:
create table hdocs ( id number primary key, fmt varchar2(10), text varchar2(80) );
Assuming you are indexing mostly Word documents, you specify BINARY
in the format column to filter the Word documents. Alternatively, to have the AUTO_FILTER
ignore an HTML document, specify TEXT
in the format column.
For example, the following statements add two documents to the text table, assigning one format as BINARY
and the other TEXT
:
insert into hdocs values(1, 'binary', '/docs/myword.doc'); insert in hdocs values (2, 'text', '/docs/index.html'); commit;
To create the index, use CREATE INDEX
and specify the format column name in the parameter string:
create index hdocsx on hdocs(text) indextype is ctxsys.context parameters ('datastore ctxsys.directory_datastore filter ctxsys.auto_filter format column fmt');
If you do not specify TEXT
or BINARY
for the format column, BINARY
is used.
Note:
You need not specify the format column in CREATE
INDEX
when using the AUTO_FILTER
.
2.4.1.4 AUTO_FILTER and Character Set Conversion With AUTO_FILTER
The AUTO_FILTER
converts documents to the database character set when the document format column is set to TEXT
. In this case, the AUTO_FILTER
looks at the charset column to determine the document character set.
If the charset column value is not an Oracle Text character set name, the document is passed through without any character set conversion.
Note:
You need not specify the charset column when using the AUTO_FILTER
.
2.4.2 NULL_FILTER
Use the NULL_FILTER
type when plain text or HTML is to be indexed and no filtering needs to be performed. NULL_FILTER
has no attributes.
NULL_FILTER and Indexing HTML Documents
If your document set is entirely HTML, Oracle recommends that you use the NULL_FILTER
in your filter preference.
For example, to index an HTML document set, specify the system-defined preferences for NULL_FILTER
and HTML_SECTION_GROUP
as follows:
create index myindex on docs(htmlfile) indextype is ctxsys.context parameters('filter ctxsys.null_filter section group ctxsys.html_section_group');
See Also:
For more information on section groups and indexing HTML documents, see "Section Group Types".
2.4.3 MAIL_FILTER
Use MAIL_FILTER
to transform RFC-822, RFC-2045 messages into indexable text.
The following limitations apply to the input:
-
Documents must be US-ASCII
-
Lines must not be longer than 1024 bytes
-
Documents must be syntactically valid with regard to RFC-822.
Behavior for invalid input is not defined. Some deviations may be robustly handled by the filter without error. Others may result in a fetch-time or filter-time error.
Note:
Starting with Oracle Database 18c, the use ofMAIL_FILTER
in Oracle Text is deprecated. Before adding email to the database, filter e-mails to indexable plain text, or to HTML.MAIL_FILTER
is based on an obsolete email protocol, RFC-822. Modern email systems do not support RFC-822. There is no replacement.2.4.3.1 MAIL_FILTER Attributes
The MAIL_FILTER
has the attributes shown in Table 2-12.
Table 2-12 MAIL_FILTER Attributes
Attribute | Attribute Value |
---|---|
|
Specify a colon-separated list of fields to preserve in the output. These fields are transformed to tag markup. For example, if
becomes:
Only top-level fields are transformed in this way. |
|
Specify a timeout value for the |
|
Specify either This attribute replaces the previous |
|
Specify how fields occurring in lower-level parts and identified by the Possible values include |
2.4.3.2 MAIL_FILTER Behavior
This filter behaves in the following way for each document:
-
Read and remove header fields
-
Decode message body if needed, depending on Content-transfer-encoding field
-
Take action depending on the Content-Type field value and the user-specified behavior specified in a mail filter configuration file. (See "About the Mail Filter Configuration File".) The possible actions are:
-
produce the body in the output text (
INCLUDE
). If no character set is encountered in theINCLUDE
parts in the Content-Type header field, then Oracle defaults to the value specified in the character set column in the base table. Name your populated character set column in the parameter string of theCREATE
INDEX
command. -
AUTO_FILTER
the body contents (AUTO_FILTER
directive). -
remove the body contents from the output text (
IGNORE
)
-
-
If no behavior is specified for the type in the configuration file, then the defaults are as follows:
-
text/*: produce body in the output text
-
application/*:
AUTO_FILTER
the body contents -
image/*, audio/*, video/*, model/*: ignore
-
-
Multipart messages are parsed, and the mail filter applied recursively to each part. Each part is appended to the output.
-
All text produced will be charset-converted to the database character set, if needed.
2.4.3.3 About the Mail Filter Configuration File
The MAIL_FILTER
filter makes use of a mail filter configuration file, which contains directives specifying how a mail document should be filtered.
The mail filter configuration file is a editable text file. Here you can override default behavior for each Content-Type. The configuration file also contains IANA-to-Oracle Globalization Support character set name mappings.
The location of the file must be in ORACLE_HOME
/ctx/config. The name of the file to use is stored in the new system parameter MAIL_FILTER_CONFIG_FILE
. On install, this is set to drmailfl.txt, which has useful default contents.
Oracle recommends that you create your own mail filter configuration files to avoid overwrite by the installation of a new version or patch set. The mail filter configuration file should be in the database character set.
Mail File Configuration File Structure
The file has two sections, BEHAVIOR
and CHARSETS
. Indicate the start of the behavior section as follows:
[behavior]
Each line following starts with a mime type, then whitespace, then behavior specification. The MIME
type can be a full TYPE
/SUBTYPE
or just TYPE
, which will apply to all subtypes of that type. TYPE
/SUBTYPE
specification overrides TYPE
specification, which overrides default behavior. Behavior can be INCLUDE
, AUTO_FILTER
, or IGNORE
(see "MAIL_FILTER Behavior" for definitions). For instance:
application/zip IGNORE application/msword AUTO_FILTER model IGNORE
You cannot specify behavior for "multipart" or "message" types. If you do, such lines are ignored. Duplicate specification for a type replaces earlier specifications.
Comments can be included in the mail configuration file by starting lines with the # symbol.
The charset mapping section begins with
[charsets]
Lines consist of an IANA name, then whitespace, then an Oracle Globalization Support charset name, like:
US-ASCII US7ASCI ISO-8859-1 WE8ISO8859P1
This file is the only way the mail filter gets the mappings. There are no defaults.
When you change the configuration file, the changes affect only the documents indexed after that point. You must flush the shared pool after changing the file.
2.4.3.4 Mail_Filter Example
Suppose there is an e-mail with the following form, in which other e-mails with different subject lines are attached to this e-mail:
To: somebody@someplace Subject: mainheader Content-Type: multipart/mixed . . . Content-Type: text/plain X-Ref: some_value Subject: subheader 1 . . . Content-Type: text/plain X-Control: blah blah blah Subject: subheader 2 . . .
Set INDEX_FIELDS
to be "Subject" and, initially, PART_FIELD_STYLE
to IGNORE
.
CTX_DDL.CREATE_PREFERENCE('my_mail_filt', 'mail_filter'); CTX_DDL_SET_ATTRIBUTE(my_mail_filt', 'INDEX_FILES', 'subject'); CTX_DDL.SET ATTRIBUTE ('my_mail_filt', 'PART_FIELD_STYLE', 'ignore');
Now when the index is created, the file will be indexed as follows:
<SUBJECT>mainheader</SUBJECT>
If PART_FIELD_STYLE
is instead set to TAG
, this becomes:
<SUBJECT>mainheader</SUBJECT> <SUBJECT>subheader1</SUBJECT> <SUBJECT>subheader2</SUBJECT>
If PART_FIELD_STYLE
is set to FIELD
instead, this is the result:
<SUBJECT>mainheader<SUBJECT> SUBJECT:subheader1 SUBJECT:subheader2
Finally, if PART_FIELD_STYLE
is instead set to TEXT
, then the result is:
<SUBJECT>mainheader</SUBJECT> subheader1 subheader2
2.4.4 USER_FILTER
Use the USER_FILTER
type to specify an external filter for filtering documents in a column.
This section contains the following topics.
2.4.4.1 USER_FILTER Attributes
USER_FILTER
has the following attribute:
Table 2-13 USER_FILTER Attribute
Attribute | Attribute Value |
---|---|
|
Specify the name of the filter executable. |
WARNING:
The USER_FILTER
type introduces the potential for security threats. A database user granted the CTXAPP role could potentially use USER_FILTER
to load a malicious application. Therefore, the DBA must safeguard against any combination of input and output file parameters that would enable the named filter executable to compromise system security.
- command
-
Specify the executable for the single external filter that is used to filter all text stored in a column. If more than one document format is stored in the column, then the external filter specified for
command
must recognize and handle all such formats.The executable that you specify must exist in the
$ORACLE_HOME/ctx/bin
directory on UNIX, and in the%ORACLE_HOME%/ctx/bin
directory on Windows.You must create your user-filter command with two parameters:
-
The first parameter is the name of the input file to be read.
-
The second parameter is the name of the output file to be written to.
If all the document formats are supported by
AUTO_FILTER
, then useAUTO_FILTER
instead ofUSER_FILTER
, unless additional tasks besides filtering are required for the documents. -
2.4.4.2 Using USER_FILTER with Charset and Format Columns
USER_FILTER
bypasses documents that do not need to be filtered. Its behavior is sensitive to the values of the format and charset columns. In addition, USER_FILTER
performs character set conversion according to the charset column values.
2.4.4.3 USER_FILTER and Explicitly Bypassing Plain Text or HTML in Mixed Format Columns
A mixed-format column is a text column containing more than one document format, such as a column that contains Microsoft Word, PDF, plain text, and HTML documents.
The USER_FILTER
executable can index mixed-format columns, automatically bypassing textual documents. However, if you prefer not to depend on the built-in bypass mechanism, you can explicitly tag your rows as text and cause the USER_FILTER
executable to ignore the row and not process the document in any way.
The format column in the base table enables you to specify the type of document contained in the text column. You can specify the following document types: TEXT
, BINARY
, and IGNORE
. During indexing, the USER_FILTER
executable ignores any document typed TEXT
, assuming the charset column is not specified. (The difference between a document with a TEXT
format column type and one with an IGNORE
type is that the TEXT
document is indexed, but ignored by the filter, while the IGNORE
document is not indexed at all. Use IGNORE
to overlook documents such as image files, or documents in a language that you do not want to index. IGNORE
can be used with any filter type.
To set up the USER_FILTER
bypass mechanism, you must create a format column in your base table. For example:
create table hdocs ( id number primary key, fmt varchar2(10), text varchar2(80) );
Assuming you are indexing mostly Word documents, you specify BINARY
in the format column to filter the Word documents. Alternatively, to have the USER_FILTER
executable ignore an HTML document, specify TEXT
in the format column.
For example, the following statements add two documents to the text table, assigning one format as BINARY
and the other TEXT
:
insert into hdocs values(1, 'binary', '/docs/myword.doc'); insert into hdocs values(2, 'text', '/docs/index.html'); commit;
Assuming that this file is named upcase.pl
, create the filter preference as follows:
ctx_ddl.create_preference ( preference_name => 'USER_FILTER_PREF', object_name => 'USER_FILTER' ); ctx_ddl.set_attribute ('USER_FILTER_PREF', 'COMMAND', 'upcase.pl');
To create the index, use CREATE
INDEX
and specify the format column name in the parameter string:
create index hdocsx on hdocs(text) indextype is ctxsys.context parameters ('datastore ctxsys.directory_datastore filter 'USER_FILTER_PREF' format column fmt');
If you do not specify TEXT
or BINARY
for the format column, BINARY
is used.
2.4.4.4 Character Set Conversion with USER_FILTER
The USER_FILTER
executable converts documents to the database character set when the document format column is set to TEXT
. In this case, the USER_FILTER
executable looks at the charset column to determine the document character set.
If the charset column value is not an Oracle Text character set name, the document is passed through without any character set conversion.
2.4.4.5 User Filter Example
The following example shows a Perl script to be used as the user filter. This script converts the input text file specified in the first argument to uppercase and writes the output to the location specified in the second argument.
#!/usr/local/bin/perl open(IN, $ARGV[0]); open(OUT, ">".$ARGV[1]); while (<IN>) { tr/a-z/A-Z/; print OUT; } close (IN); close (OUT);
Assuming that this file is named upcase.pl
, create the filter preference as follows:
begin ctx_ddl.create_preference ( preference_name => 'USER_FILTER_PREF', object_name => 'USER_FILTER' ); ctx_ddl.set_attribute ('USER_FILTER_PREF','COMMAND','upcase.pl'); end;
Create the index in SQL*Plus as follows:
create index user_filter_idx on user_filter ( docs ) indextype is ctxsys.context parameters ('FILTER USER_FILTER_PREF');
2.4.5 PROCEDURE_FILTER
Use the PROCEDURE_FILTER
type to filter your documents with a stored procedure. The stored procedure is called each time a document needs to be filtered.
This section contains the following topics.
2.4.5.1 PROCEDURE_FILTER Attributes
Table 2-14 lists the attributes for PROCEDURE_FILTER
.
Table 2-14 PROCEDURE_FILTER Attributes
Attribute | Purpose | Allowable Values |
---|---|---|
|
Name of the filter stored procedure. |
Any procedure. The procedure can be a PL/SQL stored procedure. |
|
Type of input argument for stored procedure. |
|
|
Type of output argument for stored procedure. |
|
|
Include rowid parameter? |
|
|
Include format parameter? |
|
|
Include charset parameter? |
|
- procedure
-
Specify the name of the stored procedure to use for filtering. The procedure can be a PL/SQL stored procedure. The procedure can be a safe callout, or call a safe callout.
With the
rowid_parameter
,format_parameter
, andcharset_parameter
set to FALSE, the procedure can have one of the following signatures:PROCEDURE(IN BLOB, IN OUT NOCOPY CLOB) PROCEDURE(IN CLOB, IN OUT NOCOPY CLOB) PROCEDURE(IN VARCHAR, IN OUT NOCOPY CLOB) PROCEDURE(IN BLOB, IN OUT NOCOPY VARCHAR2) PROCEDURE(IN CLOB, IN OUT NOCOPY VARCHAR2) PROCEDURE(IN VARCHAR2, IN OUT NOCOPY VARCHAR2) PROCEDURE(IN BLOB, IN VARCHAR2) PROCEDURE(IN CLOB, IN VARCHAR2) PROCEDURE(IN VARCHAR2, IN VARCHAR2)
The first argument is the content of the unfiltered row, output by the datastore. The second argument is for the procedure to pass back the filtered document text.
The procedure attribute is mandatory and has no default.
- input_type
-
Specify the type of the input argument of the filter procedure. You can specify one of the following types:
Type Description procedure
Name of the filter stored procedure.
input_type
Type of input argument for stored procedure.
output_type
Type of output argument for stored procedure.
rowid_parameter
Include rowid parameter?
The
input_type
attribute is not mandatory. If not specified, thenBLOB
is the default. - output_type
-
Specify the type of output argument of the filter procedure. You can specify one of the following types:
Type Description CLOB
The output argument is
IN
OUT
NOCOPY
CLOB
. Your procedure must write the filtered content to theCLOB
passed in.VARCHAR2
The output argument is
IN
OUT
NOCOPY
VARCHAR2
. Your procedure must write the filtered content to theVARCHAR2
variable passed in.FILE
The output argument must be
IN
VARCHAR2
. On entering the filter procedure, the output argument is the name of a temporary file. The filter procedure must write the filtered contents to this named file.Using a FILE output type is useful only when the procedure is a safe callout, which can write to the file.
The
output_type
attribute is not mandatory. If not specified, thenCLOB
is the default. - rowid_ parameter
-
When you specify TRUE, the rowid of the document to be filtered is passed as the first parameter, before the input and output parameters.
For example, with
INPUT_TYPE
BLOB
,OUTPUT_TYPE
CLOB
, andROWID_PARAMETER
TRUE
, the filter procedure must have the signature as follows:procedure(in rowid, in blob, in out nocopy clob)
This attribute is useful for when your procedure requires data from other columns or tables. This attribute is not mandatory. The default is
FALSE
. - format_parameter
-
When you specify
TRUE
, the value of the format column of the document being filtered is passed to the filter procedure before input and output parameters, but after the rowid parameter, if enabled.Specify the name of the format column at index time in the parameters string, using the keyword
'format column <columnname>'
. The parameter type must beIN
VARCHAR2
.The format column value can be read by means of the rowid parameter, but this attribute enables a single filter to work on multiple table structures, because the format attribute is abstracted and does not require the knowledge of the name of the table or format column.
FORMAT_PARAMETER
is not mandatory. The default isFALSE
. - charset_parameter
-
When you specify
TRUE
, the value of the charset column of the document being filtered is passed to the filter procedure before input and output parameters, but after the rowid and format parameter, if enabled.Specify the name of the charset column at index time in the parameters string, using the keyword
'charset column <columnname>'
. The parameter type must beIN
VARCHAR2
.The
CHARSET_PARAMETER
attribute is not mandatory. The default is FALSE.
2.4.5.2 PROCEDURE_FILTER Parameter Order
ROWID_PARAMETER
, FORMAT_PARAMETER
, and CHARSET_PARAMETER
are all independent. The order is rowid, the format, then charset. However, the filter procedure is passed only the minimum parameters required.
For example, assume that INPUT_TYPE
is BLOB
and OUTPUT_TYPE
is CLOB
. If your filter procedure requires all parameters, then the procedure signature must be:
(id IN ROWID, format IN VARCHAR2, charset IN VARCHAR2, input IN BLOB, output IN OUT NOCOPY CLOB)
If your procedure requires only the ROWID
, then the procedure signature must be:
(id IN ROWID,input IN BLOB, output IN OUT NOCOPY CLOB)
2.4.5.3 PROCEDURE_FILTER Execute Requirements
To create an index using a PROCEDURE_FILTER
preference, the index owner must have execute permission on the procedure.
2.4.5.4 PROCEDURE_FILTER Error Handling
The filter procedure can raise any errors needed through the normal PL/SQL raise_application_error
facility. These errors are propagated to the CTX_USER_INDEX_ERRORS view or reported to the user, depending on how the filter is invoked.
2.4.5.5 PROCEDURE_FILTER Preference Example
Consider a filter procedure CTXSYS.NORMALIZE
that you define with the following signature:
PROCEDURE NORMALIZE(id IN ROWID, charset IN VARCHAR2, input IN CLOB, output IN OUT NOCOPY VARCHAR2);
To use this procedure as your filter, set up your filter preference as follows:
begin ctx_ddl.create_preference('myfilt', 'procedure_filter'); ctx_ddl.set_attribute('myfilt', 'procedure', 'normalize'); ctx_ddl.set_attribute('myfilt', 'input_type', 'clob'); ctx_ddl.set_attribute('myfilt', 'output_type', 'varchar2'); ctx_ddl.set_attribute('myfilt', 'rowid_parameter', 'TRUE'); ctx_ddl.set_attribute('myfilt', 'charset_parameter', 'TRUE'); end;
2.5 Lexer Types
Use the lexer preference to specify the language of the text to be indexed. To create a lexer preference, you must use one of these lexer types.
2.5.1 AUTO_LEXER
Identifies the language being indexed by examining the content, and applies suitable options (including stemming) for that language. Works best where each document contains a single-language, and has at least a couple of paragraphs of text to aid identification.
Use the AUTO_LEXER
type to index columns that contain documents of different languages. It performs language identification, word segmentation, document analysis, and stemming. The AUTO_LEXER
also enables customization of these components. Although parts-of-speech information that is generated by the AUTO_LEXER
is not exposed for your use, AUTO_LEXER
uses it for context-sensitive or tagged stemming.
Note:
TheAUTO_LEXER
type is currently not supported on Oracle Database Express Edition (Oracle Database XE).
2.5.1.1 AUTO_LEXER Language Support
At index time, AUTO_LEXER
automatically detects the language of the document, and tokenizes and stems the document appropriately. To specify an AUTO_LEXER
dictionary, use the name of the dictionary you created instead of the filename for the dictionary.
At query time, the language of the query is inherited from the query template. If the query template is not used, or if no language is specified in the query template, then the language of the query is inherited from the session language. Table 2-15 lists the supported languages.
Note:
Note that dictionary data will not be processed until index/policy creation time or ALTER INDEX
time. Errors in dictionary data format will be caught at index/policy creation time or ALTER INDEX
time and reported as: DRG-13710: Syntax Error in Dictionary.
Table 2-15 Languages Supported for AUTO_LEXER
Language | Language |
---|---|
ARABIC |
NYNORSK |
BOKMAL |
PERSIAN |
CROATIAN |
SERBIAN |
DANISH |
SLOVAK |
FINNISH |
SLOVENIAN |
HEBREW |
THAI |
CATALAN |
KOREAN |
CZECH |
POLISH |
DUTCH |
PORTUGUESE |
ENGLISH |
ROMANIAN |
FRENCH |
RUSSIAN |
GERMAN |
SIMPLIFIED CHINESE (See Note) |
GREEK |
SPANISH |
HUNGARIAN |
SWEDISH |
ITALIAN |
TRADITIONAL CHINESE (See Note) |
JAPANESE |
TURKISH |
Note:
Due to the limitation of 30 characters for the string, Traditional Chinese must be specified as trad_chinese
. Simplified Chinese must be specified as simp_chinese
.
2.5.1.2 AUTO_LEXER Attributes Inherited from BASIC_LEXER
The following attributes are used in the same way and have the same effect on the AUTO_LEXER
as their corresponding attributes in BASIC_LEXER
:
-
printjoins
-
skipjoins
-
base_letter
-
base_letter_type
-
override_base_letter
-
mixed_case
-
alternate_spelling
See Also:
"BASIC_LEXER" and Table 2-20
2.5.1.3 AUTO_LEXER Language-Independent Attributes
Table 2-16 lists the language-independent attributes available in the AUTO_LEXER
.
Table 2-16 AUTO_LEXER Language-Independent Attributes
Attribute | Attribute Value | Description |
---|---|---|
|
<characters> (space-delimited string) |
Specifies the possible languages of the input documents. If no language is specified, then If one language is specified, then the language is set manually and If more than one language is specified, then Note: The automatic detection of language is statistically based and, thus, inherently imperfect. |
|
NO (disabled) |
Specifies whether the derivational stemming should be used or not. Currently, derivational stemming is only available for English. Hence, the Also, when derivational stemming is performed, tagging and tag stemming is not used. As a result, the tagging and tagged stemming client dictionary has no effect on the stemming result. |
|
YES (default) |
Specifies whether the derivational stemming should be used or not. Currently, derivational stemming is only available for English. Hence, the Also, when derivational stemming is performed, tagging and tag stemming is not used. As a result, the tagging and tagged stemming client dictionary has no effect on the stemming result. |
|
NO (disabled) |
Specifies whether German de-compounding should be performed in the stemmer or not. |
|
YES (default, enabled for German only) |
Specifies whether German de-compounding should be performed in the stemmer or not. |
|
NO (disabled) |
Specifies whether an index stemmer should be used. If specified as YES, then the stemmer that corresponds to the document language will be used and the stemmer will always be configured to maximize document recall. Note that this means that the stemmer attribute of If specified as NO, then queries with stem operators will use the word list stemming to try to stem the tokens. If word list stemming is not available, then the stem operator will be ignored. For documents in Swedish and Dutch, if the |
|
YES (default) |
Specifies whether an index stemmer should be used. If specified as YES, then the stemmer that corresponds to the document language will be used and the stemmer will always be configured to maximize document recall. Note that this means that the stemmer attribute of If specified as NO, then queries with stem operators will use the word list stemming to try to stem the tokens. If word list stemming is not available, then the stem operator will be ignored. For documents in Swedish and Dutch, if the |
|
NO (disabled) |
Specify whether characters that have diacritical marks (umlauts, cedillas, acute accents, and so on) are converted to their base form before being stored in the Text index. |
|
YES (enabled) |
Specify whether characters that have diacritical marks (umlauts, cedillas, acute accents, and so on) are converted to their base form before being stored in the Text index. |
|
GENERIC (default) |
The |
|
SPECIFIC |
The |
|
TRUE FALSE (default) |
When |
|
NO (disabled) |
Specify whether the lexer leaves the tokens exactly as they appear in the text or converts the tokens to all uppercase. The default is NO (tokens are converted to all uppercase). |
|
YES (enabled) |
Specify whether the lexer leaves the tokens exactly as they appear in the text or converts the tokens to all uppercase. |
|
GERMAN (German alternate spelling) |
Specifies whether German alternate spelling should be used or not. |
|
SWEDISH (Swedish alternate spelling) |
Specifies whether Swedish alternate spelling should be used or not. |
|
NONE (No alternate spelling, default) |
The default is NONE. No alternate spelling is specified. |
|
characters |
Specify the non alphanumeric characters that, when they appear anywhere in a word (beginning, middle, or end), are processed as alphanumeric and included with the token in the Text index. This includes printjoins that occur consecutively. See Basic Lexer ""printjoins"". |
|
characters |
Specify the non-alphanumeric characters that, when they appear within a word, identify the word as a single token; however, the characters are not stored with the token in the Text index. See Basic Lexer ""skipjoins"". |
2.5.1.4 AUTO_LEXER Language-Dependent Attributes
AUTO_LEXER provides language-dependent attributes for the languages specified in Table 2-15.
Table 2-17 lists the language-dependent attributes available in the AUTO_LEXER
. The <language> variable in the attribute name refers to any of the supported language names that are listed in Table 2-15.
Note:
Attribute names must not exceed 30 characters. Therefore, where the <language> variable is specified, the language name may need to be abbreviated in certain instances. For example, traditional_chinese
should be abbreviated to trad_chinese
and simplified_chinese
should be abbreviated to simp_chinese
.
Table 2-17 AUTO_LEXER Language-Dependent Attributes
Attribute | Attribute Value | Description |
---|---|---|
<language> |
characters (space-delimited string) |
Specifies the list of inflectional prefixes that, when enclosed by parentheses, are kept together with the base word. For example, (re) analyze. |
<language> |
characters (space-delimited string) |
Specifies the list of inflectional suffixes that, when enclosed by parentheses are kept together with the base word. For example, file(s). |
<language> |
characters (space-delimited string) |
Specifies punctuation that breaks sentences. |
<language> |
characters (space-delimited string) |
Specifies abbreviations that do not end sentences. |
Table 2-18 Default Values for AUTO_LEXER Language-Dependent Attributes
Attribute | Language | Default Value |
---|---|---|
<language> |
All languages |
None |
<language> |
English |
s es er |
<language> |
Spanish |
ba n s es |
<language> |
Portuguese |
s es |
<language> |
German |
in innen |
<language> |
French |
ne e |
<language> |
All other languages |
None |
<language> |
English |
. ? ! |
<language> |
Catalan, Czech, Dutch, Greek, Hungarian, Polish, Romanian, Russian, Turkish |
. ? ! - -- |
<language> |
French, German, Italian, Korean, Portuguese, Spanish, Swedish |
, ? ! |
<language> |
Japanese |
|
<language> |
Simplified Chinese Abbreviate to: simp_chinese |
|
<language> |
Traditional Chinese Abbreviate to: trad_chinese |
|
<language> |
Polish, Romanian, Russian, Turkish |
e.g. i.e. viz. a.k.a. |
<language> |
Catalan |
R.D. pp. |
<language> |
Czech, Greek, Hungarian |
e.g. i.e. viz. a.k.a. |
<language> |
Dutch |
f.eks. f. eks. inkl. sr. skuesp. sekr. prof. mus. lrs. logr. kgl. insp. hr. hrs. gdr. frk. fr. forst. forf. fm. fmd. esq. d.æ d.æ. d.y. dr. dir. dept.chef civiling. bibl. ass. admn. adj. Skt. H.K.H. |
<language> |
English, Japanese, Simplified Chinese (abbreviate to simp_chinese), Traditional Chinese (abbreviate to trad_chinese) |
e.g. i.e. viz. a.k.a. Adm. Br. Capt. Cdr. Cmdr. Col. Comdr. Comdt. Dr. Drs. Fr. Gen. Gov. Hon. Ins. Lieut. Lt. Maj. Messrs. Mdm. Mlle. Mlles. Mme. Mmes. Mr. Mrs. Ms. Pres. Prof. Profs. Pvt. Rep. Rev. Revd. Secy. Sen. Sgt. Sra. Srta. St. Ste. |
<language> |
French |
c.-à-d. cf. e.g. ex. i.e. Pr. Prof. M. Mr. Mrs. Mme Mmes Mlle Mlles Mgr. MM. Lieut. Gén. Dr. Col. |
<language> |
German |
ca. bzw. e.g. i.e. inkl. Fr. Frl. Mme. Mile. Mag. Stud. Tel. Hr. Hrn. apl.Prof. Prof. |
<language> |
Italian |
e.g. i.e. pag. pagg. tel. T.V. N.H. N.D. comm. col. cav. cap. geom. gen. ing. jr. mr. mons. mar. magg. prof. prof.ssa prof.sse proff. pres. perito ind. p. p.i. sr. s.ten. sottoten. sig. serg. sen. segr. sac. ten. uff. vicepres. vesc. S.S. S.E. avv. app. amm. arch. on. dir. dott. dott.ssa dr. rag. |
<language> |
Korean |
e.g. i.e. a.k.a. Dr. Mr. Mrs. Ms. Prof. |
<language> |
Portuguese |
cf. Cf. e.g. E.g. i.é. I.é. p.ex. P.ex. pág. pag. Pág. Pag. tel. telef. Tel. Telef. sr. srs. sra. mr. eng. dr. dra. Dr. Dra. V.Ex. V.Exa. S. N. S. Mrs. Eng. Ex. Exa. |
<language> |
Spanish |
e.g. i.e. ej. p.ej. pág. págs. tel. tfno. Fr. Ldo. Lda. Lic. Pbro. D. Dña. Dr. Dres. Dra. Dras. Dn. Mons. Rvdo. Sto. Sta. Sr. Srs. Srta. Srtas. Sres. Sra. Sras. Excmo. Excma. Ilmo. Ilma. Sto. Sta. |
<language> |
Swedish |
inkl. prof. hrr. hr. Hrr. Hr. dr. Dr. |
Examples for AUTO_LEXER Language-Dependent Attributes
Example 2-1 ctx_ddl.create_preference to associate a dictionary with an index
exec CTX_DDL.CREATE_PREFERENCE('A_LEX', 'AUTO_LEXER'); exec CTX_ANL. ADD_DICTIONARY('MY_ENGLISH', 'ENGLISH', lobloc); select * from CTX_USR_ANL_DICTS; exec CTX_DDL.SET_ATTRIBUTE('A_LEX', 'english_dictionary', 'MY_ENGLISH' );
Example 2-2 <language>_prefix_morphemes
ctx_ddl.set_attribute( 'a_lex', 'english_prefix_morphemes', 're' );
Example 2-3 <language>_suffix_morphemes
ctx_ddl.set_attribute( 'a_lex', 'english_suffix_morphemes', 's es' );
Example 2-4 <language>_punctuations
ctx_ddl.set_attribute( 'a_lex', 'english_punctuations', '. ? !' );
Example 2-5 <language>_non_sentence_ending_abbrev
ctx_ddl.set_attribute( 'a_lex', 'english_non_sentence_ending_abbrev', 'e.g. a.k.a. Dr.' );
2.5.1.5 AUTO_LEXER Dictionary Attribute
The dictionary attribute is language-specific and is used to set the name of the language dictionary. The <language>_dictionary
attribute specifies one language dictionary for the supported languages as listed in Table 2-19.
The <language>_dictionary
attribute has the following behavior:
-
The <language> value of the attribute specifies only the dictionary name, not the location. For example,
dutch_dictionary
specifies that the Dutch dictionary is to be used. -
The
set_attribute
method does not load the dictionary; it only records the dictionary name. Therefore, the dictionary must be at the specified location when the dictionary is needed. Otherwise, an error will be raised.
Table 2-19 Supported Languages for AUTO_LEXER Dictionary Attribute
Language Attribute | Language Attribute |
---|---|
Catalan |
Korean |
Czech |
Polish |
Dutch |
Portuguese |
English |
Romanian |
French |
Russian |
German |
Simplified Chinese |
Greek |
Spanish |
Hungarian |
Swedish |
Italian |
Traditional Chinese |
Japanese |
Turkish |
2.5.2 BASIC_LEXER
Extracts tokens from text in languages, such as English and most of the western European languages that use whitespace-delimited words.
Use the BASIC_LEXER
type to identify tokens for creating Text indexes for English and all other supported whitespace-delimited languages. The BASIC_LEXER
also enables base-letter conversion, composite word indexing, case-sensitive indexing and alternate spelling for whitespace-delimited languages that have extended character sets.
In English and French, you can use the BASIC_LEXER
to enable theme indexing.
Note:
Any processing that the lexer does to tokens before indexing (for example, removal of characters, and base-letter conversion) are also performed on query terms at query time. This ensures that the query terms match the form of the tokens in the Text index.
BASIC_LEXER
supports any database character set.
This section contains the following topics.
2.5.2.1 BASIC_LEXER Attributes
BASIC_LEXER
has the attributes shown in Table 2-20.
Table 2-20 BASIC_LEXER Attributes
Attribute | Attribute Value |
---|---|
|
characters |
|
characters |
|
characters |
|
characters |
|
characters |
|
characters |
|
non alphanumeric characters that occur at the beginning of a token (string) |
|
non alphanumeric characters that occur at the end of a token (string) |
|
characters (string) |
|
NEWLINE (\n) CARRIAGE_RETURN (\r) |
|
NO (disabled) |
|
YES (enabled) |
|
GENERIC (default) |
|
SPECIFIC |
|
TRUE FALSE (default) |
|
NO (disabled) |
|
YES (enabled) |
|
DEFAULT (no composite word indexing, default) |
|
GERMAN (German composite word indexing) |
|
DUTCH (Dutch composite word indexing) |
Use the numeric value in a string or the string value. |
NONE ENGLISH DERIVATIONAL DUTCH FRENCH GERMAN ITALIAN SPANISH CATALAN CZECH GREEK HUNGARIAN POLISH PORTUGUESE ROMANIAN RUSSIAN SWEDISH (see Note) DERIVATIONAL_NEW (see Note) DUTCH_NEW (see Note) ENGLISH_NEW (see Note) FRENCH_NEW (see Note) GERMAN_NEW (see Note) ITALIAN_NEW (see Note) SPANISH_NEW (see Note) TURKISH Note: De-compounding word stemming is automatically performed when Note: Seven of the |
|
YES (enabled) |
|
NO (disabled, default) |
|
YES (enabled, default) |
|
NO (disabled) |
|
YES (enabled, default) |
|
NO (disabled) |
|
AUTO (default) |
|
(any Globalization Support language) |
|
GERMAN (German alternate spelling) |
|
DANISH (Danish alternate spelling) |
|
SWEDISH (Swedish alternate spelling) |
|
NONE (No alternate spelling, default) |
|
YES NO (default) |
- continuation
-
Specify the characters that indicate a word continues on the next line and should be indexed as a single token. The most common continuation characters are hyphen '-' and backslash '\'.
- numgroup
-
Specify a single character that, when it appears in a string of digits, indicates that the digits are groupings within a larger single unit.
For example, comma ',' might be defined as a
numgroup
character because it often indicates a grouping of thousands when it appears in a string of digits. - numjoin
-
Specify the characters that, when they appear in a string of digits, cause Oracle Text to index the string of digits as a single unit or word.
For example, period '.' can be defined as a
numjoin
character because it often serves as a decimal point when it appears in a string of digits.Note:
The default values for
numjoin
andnumgroup
are determined by the globalization support initialization parameters that are specified for the database.In general, a value need not be specified for either
numjoin
ornumgroup
when creating a lexer preference forBASIC_LEXER
. - printjoins
-
Specify the non alphanumeric characters that, when they appear anywhere in a word (beginning, middle, or end), are processed as alphanumeric and included with the token in the Text index. This includes
printjoins
that occur consecutively.For example, if the hyphen '-' and underscore '_' characters are defined as
printjoins
, terms such as pseudo-intellectual and _file_ are stored in the Text index as pseudo-intellectual and _file_.Note:
If a
printjoins
character is also defined as apunctuations
character, the character is only processed as an alphanumeric character if the character immediately following it is a standard alphanumeric character or has been defined as aprintjoins
orskipjoins
character. - punctuations
-
Specify a list of non-alphanumeric characters that, when they appear at the end of a word, indicate the end of a sentence. The defaults are period '.', question mark '?', and exclamation point '!'.
Characters that are defined as
punctuations
are removed from a token before text indexing. However, if apunctuations
character is also defined as aprintjoins
character, then the character is removed only when it is the last character in the token.For example, if the period (.) is defined as both a
printjoins
and apunctuations
character, then the following transformations take place during indexing and querying as well:Token Indexed Token .doc
.doc
dog.doc
dog.doc
dog..doc
dog..doc
dog.
dog
dog...
dog..
In addition,
BASIC_LEXER
usepunctuations
characters in conjunction withnewline
andwhitespace
characters to determine sentence and paragraph delimiters for sentence/paragraph searching. - skipjoins
-
Specify the non-alphanumeric characters that, when they appear within a word, identify the word as a single token; however, the characters are not stored with the token in the Text index.
For example, if the hyphen character '-' is defined as a
skipjoins
, then the word pseudo-intellectual is stored in the Text index as pseudointellectual.Note:
Printjoins
andskipjoins
are mutually exclusive. The same characters cannot be specified for both attributes. - startjoins/endjoins
-
For
startjoins
, specify the characters that when encountered as the first character in a token explicitly identify the start of the token. The character, as well as any otherstartjoins
characters that immediately follow it, is included in the Text index entry for the token. In addition, the firststartjoins
character in a string ofstartjoins
characters implicitly ends the previous token.For
endjoins
, specify the characters that when encountered as the last character in a token explicitly identify the end of the token. The character, as well as any otherstartjoins
characters that immediately follow it, is included in the Text index entry for the token.The following rules apply to both
startjoins
andendjoins
:
-
The characters specified for
startjoins
/endjoins
cannot occur in any of the other attributes forBASIC_LEXER
. -
startjoins
/endjoins
characters can occur only at the beginning or end of tokens
Printjoins differ from endjoins and startjoins in that position does not matter. For example, $35 will be indexed as one token if $ is a startjoin
or a printjoin
, but as two tokens if it is defined as an endjoin
.
- whitespace
-
Specify the characters that are treated as blank spaces between tokens.
BASIC_LEXER
useswhitespace
characters in conjunction withpunctuations
andnewline
characters to identify character strings that serve as sentence delimiters for sentence and paragraph searching.The predefined default values for
whitespace
arespace
andtab
. These values cannot be changed. Specifying characters aswhitespace
characters adds to these defaults. - newline
-
Specify the characters that indicate the end of a line of text.
BASIC_LEXER
usesnewline
characters in conjunction with punctuations and whitespace characters to identify character strings that serve as paragraph delimiters for sentence and paragraph searching.The only valid values for
newline
areNEWLINE
andCARRIAGE_RETURN
(for carriage returns). The default isNEWLINE
. - base_letter
-
Specify whether characters that have diacritical marks (umlauts, cedillas, acute accents, and so on) are converted to their base form before being stored in the Text index. The default is NO (base-letter conversion disabled). For more information on base-letter conversions and
base_letter_type
, see Base-Letter Conversion. - base_letter_type
-
Specify
GENERIC
orSPECIFIC
.The
GENERIC
value is the default and means that base letter transformation uses one transformation table that applies to all languages. For more information on base-letter conversions andbase_letter_type
, see "Base-Letter Conversion". - override_base_letter
-
When
base_letter
is enabled at the same time asalternate_spelling
, it is sometimes necessary to overridebase_letter
to prevent unexpected results from serial transformations. See "Overriding Alternative Spelling Features". Default isFALSE
. - mixed_case
-
Specify whether the lexer leaves the tokens exactly as they appear in the text or converts the tokens to all uppercase. The default is NO (tokens are converted to all uppercase).
Note:
Oracle Text ensures that word queries match the case sensitivity of the index being queried. As a result, if you enable case sensitivity for your Text index, queries against the index are always case sensitive.
- composite
-
Specify whether composite word indexing is disabled or enabled for either
GERMAN
orDUTCH
text. The default isDEFAULT
(composite word indexing disabled).Words that are usually one entry in a German dictionary are not split into composite stems, while words that aren't dictionary entries are split into composite stems.
To retrieve the indexed composite stems, you must enter a stem query, such as $bahnhof. The language of the wordlist stemmer must match the language of the composite stems.
2.5.2.2 Stemming User-Dictionaries
You can create a user-dictionary for your own language to customize how words are decomposed. These dictionaries are shown in Table 2-21.
Table 2-21 Stemming User-Dictionaries
Dictionary | Stemmer |
---|---|
|
French |
|
German |
|
Dutch |
|
Italian |
|
Spanish |
|
English and Derivational |
Stemming user-dictionaries are not supported for languages other than those listed in Table 2-21.
The format for the user dictionary is as follows:
output term <tab> input term
The individual parts of the decomposed word must be separated by the # character. The following example entries are for the German word Hauptbahnhof:
Hauptbahnhof<tab>Haupt#Bahnhof Hauptbahnhofes<tab>Haupt#Bahnhof Hauptbahnhof<tab>Haupt#Bahnhof Hauptbahnhoefe<tab>Haupt#Bahnhof
- index_themes
-
Specify
YES
to index theme information in English or French. This makesABOUT
queries more precise. Theindex_themes
andindex_text
attributes cannot both beNO
. The default isNO
.You can set this parameter to
TRUE
for any index type, includingCTXCAT
. To enter anABOUT
query withCATSEARCH
, use the query template withCONTEXT
grammar. - prove_themes
-
Specify
YES
to prove themes. Theme proving attempts to find related themes in a document. When no related themes are found, parent themes are eliminated from the document.While theme proving is acceptable for large documents, short text descriptions with a few words rarely prove parent themes, resulting in poor recall performance with
ABOUT
queries.Theme proving results in higher precision and less recall (less rows returned) for
ABOUT
queries. For higher recall inABOUT
queries and possibly less precision, you can disable theme proving. Default isYES
.The
prove_themes
attribute is supported forCONTEXT
andCTXRULE
indexes. - theme_language
-
Specify which knowledge base to use for theme generation when
index_themes
is set toYES
. Whenindex_themes
isNO
, setting this parameter has no effect on anything.Specify any globalization support language or
AUTO
. You must have a knowledge base for the language you specify. This release provides a knowledge base in only English and French. In other languages, you can create your own knowledge base.See Also:
"Adding a Language-Specific Knowledge Base" in Oracle Text Utilities .
The default is
AUTO
, which instructs the system to set this parameter according to the language of the environment. - index_stems
-
Specify the stemmer to use for stem indexing. Choose one of the following stemmers: NONE, ARABIC, CATALAN, CROATIAN, CZECH, DANISH, DERIVATIONAL, DUTCH, ENGLISH, FINNISH, FRENCH, GERMAN, HEBREW, HUNGARIAN, ITALIAN, NORWEGIAN, POLISH, PORTUGUESE, ROMANIAN, SLOVAK, SLOVENIAN, SPANISH, and SWEDISH.
Tokens are stemmed to a single base form at index time in addition to the normal forms. Indexing stems enables better query performance for stem ($) queries, such as $computed.
Note:
If the index_stems
attribute is set to one of the languages with ID 8 to 33, which are listed Table 2-20, then the stemmer
attribute of BASIC_WORDLIST
will be ignored and the stemmer used by the BASIC_LEXER
will be used during query to determine the stem of the given query term.
- index_text
-
Specify
YES
to index word information. The index_themes and index_text attributes cannot both beNO
.The default is
YES
. - alternate_spelling
-
Specify either
GERMAN
,DANISH
, orSWEDISH
to enable the alternate spelling in one of these languages. Enabling alternate spelling enables you to query a word in any of its alternate forms.Alternate spelling is off by default; however, in the language-specific scripts that Oracle provides in
admin/defaults
(drdefd.sql
for German,drdefdk.sql
for Danish, anddrdefs.sql
for Swedish), alternate spelling is turned on. If your installation uses these scripts, then alternate spelling is on. However, you can specifyNONE
for no alternate spelling. For more information about the alternate spelling conventions Oracle Text uses, see Alternate Spelling. - new_german_spelling
-
Specify whether the queries using the
BASIC_LEXER
return both traditional and reformed (new) spellings of German words. Ifnew_german_spelling
is set toYES
, then both traditional and new forms of words are indexed. If it is set toNO
, then the word will be indexed only as it as provided in the query. The default isNO
.See Also:
2.5.2.3 BASIC_LEXER Example
The following example sets printjoin characters and disables theme indexing with the BASIC_LEXER
:
begin ctx_ddl.create_preference('mylex', 'BASIC_LEXER'); ctx_ddl.set_attribute('mylex', 'printjoins', '_-'); ctx_ddl.set_attribute ( 'mylex', 'index_themes', 'NO'); ctx_ddl.set_attribute ( 'mylex', 'index_text', 'YES'); end;
To create the index with no theme indexing and with printjoin characters set as described, enter the following statement:
create index myindex on mytable ( docs ) indextype is ctxsys.context parameters ( 'LEXER mylex' );
2.5.3 MULTI_LEXER
Requires a LANGUAGE
column in the table that identifies the language for each document. Each language has an associated sub-lexer, defined by the user. This lexer has no attributes.
Use MULTI_LEXER
to index text columns that contain documents of different languages. For example, use this lexer to index a text column that stores English, German, and Japanese documents.
You must have a LANGUAGE
column in your base table. To index multi-language tables, specify the LANGUAGE
column when you create the index. You must also specify the language at query time (through Session settings or a Language settings in a query template), and the queries only look for documents that are indexed using the current language.
Create a multi-lexer preference with CTX_DDL.CREATE_PREFERENCE
. Add language-specific lexers to the multi-lexer preference with the CTX_DDL.ADD_SUB_LEXER
procedure.
During indexing, the MULTI_LEXER
examines each row's language column value and switches in the language-specific lexer to process the document.
Note:
If you drop the language column from a multi-lexer indexed table, you must also drop the index and rebuild it.
The WORLD_LEXER
lexer also performs multi-language indexing, but without the need for separate LANGUAGE
columns (that is, it has automatic language detection). For more on WORLD_LEXER
, see "WORLD_LEXER".
This section contains the following topics.
2.5.3.1 MULTI_LEXER Restriction
MULTI_LEXER must have a sublexer specified for different languages. If you already know the language, you can use BASIC_LEXER as the sublexer. If the language is not known, then you use AUTO_LEXER instead of MULTI_LEXER. Hence, using AUTO_LEXER as a sublexer of MULTI_LEXER is not useful and it is disabled.
Thus, the following statements will not work and throw error DRG-13003.
exec ctx_ddl.create_preference ('multilexer', 'MULTI_LEXER'); exec ctx_ddl..create_preference('autolexer', AUTO_LEXER); exec ctx_ddl.add_sub_lexer('multilexer', 'GERMAN', 'autolexer');
2.5.3.2 MULTI_LEXER Multi-language Stoplists
When you use the MULTI_LEXER
, you can also use a multi-language stoplist for indexing.
See Also:
2.5.3.3 MULTI_LEXER Example
Create the multi-language table with a primary key, a text column, and a language column as follows:
create table globaldoc ( doc_id number primary key, lang varchar2(3), text clob );
Assume that the table holds mostly English documents, with the occasional German or Japanese document. To handle the three languages, you must create three sub-lexers, one for English, one for German, and one for Japanese:
ctx_ddl.create_preference('english_lexer','basic_lexer'); ctx_ddl.set_attribute('english_lexer','index_themes','yes'); ctx_ddl.set_attribute('english_lexer','theme_language','english'); ctx_ddl.create_preference('german_lexer','basic_lexer'); ctx_ddl.set_attribute('german_lexer','composite','german'); ctx_ddl.set_attribute('german_lexer','mixed_case','yes'); ctx_ddl.set_attribute('german_lexer','alternate_spelling','german'); ctx_ddl.create_preference('japanese_lexer','japanese_vgram_lexer');
Create the multi-lexer preference:
ctx_ddl.create_preference('global_lexer', 'multi_lexer');
Because the stored documents are mostly English, make the English lexer the default using CTX_DDL.ADD_SUB_LEXER :
ctx_ddl.add_sub_lexer('global_lexer','default','english_lexer');
Now add the German and Japanese lexers in their respective languages with CTX_DDL.ADD_SUB_LEXER procedure. Also assume that the language column is expressed in the standard ISO 639-2 language codes, so add those as alternative values.
ctx_ddl.add_sub_lexer('global_lexer','german','german_lexer','ger'); ctx_ddl.add_sub_lexer('global_lexer','japanese','japanese_lexer','jpn');
Now create the index globalx
, specifying the multi-lexer preference and the language column in the parameter clause as follows:
create index globalx on globaldoc(text) indextype is ctxsys.context parameters ('lexer global_lexer language column lang');
2.5.3.4 MULTI_LEXER and Querying Multi-Language Tables
At query time, the multi-lexer examines the language setting and uses the sub-lexer preference for that language to parse the query.
If the language is not set, then the default lexer is used. Otherwise, the query is parsed and run as usual. The index contains tokens from multiple languages, so such a query can return documents in several languages. To limit your query to a given language, use a structured clause on the language column.
If the language column is set to AUTO
, then the multi-lexer detects the language of the document for the supported languages shown in Table 2-22.
Table 2-22 Languages Supported for MULTI_LEXER Auto-detection
Language | Language |
---|---|
Arabic |
Japanese |
Bokmal (Norwegian) |
Korean |
Catalan |
Latin Serbian |
Croatian |
Nynorsk (Norwegian) |
Czech |
Polish |
Danish |
Portuguese |
Dutch |
Romanian |
English |
Russian |
German |
Slovak |
Greek |
Swedish |
Hebrew |
Thai |
Hungarian |
Traditional Chinese |
Italian |
Turkish |
2.5.4 CHINESE_VGRAM_LEXER
Extracts tokens in Chinese text for creating Oracle Text indexes.
Table 2-23 CHINESE_VGRAM_LEXER Attributes
Attribute | Attribute Value |
---|---|
|
Enable mixed-case (upper- and lower-case) searches of ASCII7 text (for example, cat and Cat). Allowable values are |
You can use this lexer if your database uses one of the following character sets:
2.5.5 CHINESE_LEXER
Identifies tokens in traditional and simplified Chinese text for creating Oracle Text indexes.
The CHINESE_LEXER
type offers the following benefits over the CHINESE_VGRAM_LEXER
:
-
generates a smaller index
-
better query response time
-
generates real word tokens resulting in better query precision
-
supports stop words
Because the CHINESE_LEXER
uses a different algorithm to generate tokens, indexing time is longer than with CHINESE_VGRAM_LEXER
.
You can use this lexer if your database character is one of the Chinese or Unicode character sets supported by Oracle.
The CHINESE_LEXER
has the following attribute:
Table 2-24 CHINESE_LEXER Attributes
Attribute | Attribute Value |
---|---|
|
Enable mixed-case (upper- and lower-case) searches of ASCII7 text (for example, cat and Cat). Allowable values are |
You can modify the existing lexicon (dictionary) used by the Chinese lexer, or create your own Chinese lexicon, with the ctxlc
command.
See Also:
2.5.6 JAPANESE_VGRAM_LEXER
Identifies tokens in Japanese for creating Oracle Text indexes. This lexer supports the stem ($) operator.
Table 2-25 JAPANESE_VGRAM_LEXER Attributes
Attribute | Attribute Value |
---|---|
|
Specify whether to consider certain Japanese blank characters, such as a full-width forward slash or a full-width middle dot, as part of the indexed token. |
|
Enable mixed-case (upper- and lower-case) searches of ASCII7 text (for example, cat and Cat). Allowable values are |
|
Specify |
|
Specify the non alphanumeric characters that, when they appear anywhere in a word (beginning, middle, or end), are processed as alphanumeric and included with the token in the Text index. This includes printjoins that occur consecutively. See Basic Lexer ""printjoins"". |
|
Specify the non-alphanumeric characters that, when they appear within a word, identify the word as a single token; however, the characters are not stored with the token in the Text index. See Basic Lexer ""skipjoins"". |
You can use this lexer if your database uses one of the following character sets:
Rules for PRINTJOIN and SKIPJOIN Characters
-
Only non-alphanumeric ASCII characters that do not include any Chinese, Japanese, or Korean characters or any full-width non-alphanumeric characters are accepted.
-
You can specify a single non-alphanumeric character or multiple non-alphanumeric characters at a time.
-
The printjoin/skipjoin will be ignored if you enter any characters that are not allowed. This includes alphanumeric characters, CJK – Chinese, Japanese, Korean – characters or full-width non-alphanumeric characters.
-
In case of duplicate non-alphanumeric characters, duplicate entries will be ignored.
Examples
Example 2-6 Using Printjoins with JAPANESE_VGRAM_LEXER
This example defines the hyphen and underscore characters as printjoins
thereby indicating that these characters must be included with the token in the Text index. Therefore, words such as web-site or web_site as indexed as web-site and web_site. Queries that search for website will not return documents containing web-site or web_site.
ctx_ddl.create_preference('mylex', 'JAPANESE_VGRAM_LEXER');
ctx_ddl.set_attribute('mylex', 'printjoins', '_-');
Example 2-7 Using Skipjoins with JAPANESE_VGRAM_LEXER
This example defines the hyphen and underscore characters as skipjoins
thereby indicating that these characters must not be included with the token in the Text index. Therefore, words such as web-site or web_site as indexed as website. Queries that search for website will return documents containing web-site or web_site.
ctx_ddl.create_preference('mylex', 'JAPANESE_VGRAM_LEXER');
ctx_ddl.set_attribute('mylex', 'skipjoins', '_-');
2.5.7 JAPANESE_LEXER
Identifies tokens in Japanese for creating Oracle Text indexes. Offers advantages over JAPANESE_VGRAM_LEXER
, such as generates a smaller index, has a better query response time, and generates real word tokens resulting in better query precision.
The JAPANESE_LEXER
type supports the stem ($) operator. Because the JAPANESE_LEXER
uses a new algorithm to generate tokens, indexing time is longer than with JAPANESE_VGRAM_LEXER
.
You can modify the existing lexicon (dictionary) used by the Japanese lexer, or create your own Japanese lexicon, with the ctxlc
command.
See Also:
This lexer has the following attributes:
Table 2-26 JAPANESE_LEXER Attributes
Attribute | Attribute Value |
---|---|
|
Specify |
|
Enable mixed-case (upper- and lower-case) searches of ASCII7 text (for example, cat and Cat). Allowable values are |
The JAPANESE_LEXER
supports the following character sets:
When you specify JAPANESE_LEXER
for creating text index, the JAPANESE_LEXER
resolves a sentence into words.
For example, the following compound word (natural language institute)
is indexed as three tokens:
To resolve a sentence into words, the internal dictionary is referenced. When a word cannot be found in the internal dictionary, Oracle Text uses the JAPANESE_VGRAM_LEXER
to resolve it.
2.5.8 KOREAN_MORPH_LEXER
Identifies tokens in Korean text for creating Oracle Text indexes.
This section contains the following topics.
2.5.8.1 KOREAN_MORPH_ LEXER Dictionaries
The KOREAN_MORPH_LEXER
uses four dictionaries:
Table 2-27 KOREAN_MORPH_LEXER Dictionaries
Dictionary | File |
---|---|
System |
|
Grammar |
|
Stopword |
|
User-defined |
|
The grammar, user-defined, and stopword dictionaries should be written using the KSC 5601 or MSWIN949 character sets. You can modify these dictionaries using the defined rules. The system dictionary must not be modified.
You can add unregistered words to the user-defined dictionary file. The rules for specifying new words are in the file.
You can use KOREAN_MORPH_LEXER
if your database uses one of the following character sets:
The KOREAN_MORPH_LEXER
enables mixed-case searches.
2.5.8.2 KOREAN_MORPH_ LEXER Unicode Support
The KOREAN_MORPH_LEXER
has the following Unicode support:
-
Words in non-KSC5601 Korean characters defined in Unicode
-
Supplementary characters
See Also:
For information on supplementary characters, see the Oracle Database Globalization Support Guide
Some Korean documents may have non-KSC5601 characters in them. As the KOREAN_MORPH_LEXER
can recognize all possible 11,172 Korean (Hangul) characters, such documents can also be interpreted by using the UTF8 or AL32UTF8 character sets.
Use the AL32UTF8 character set for your database to extract surrogate characters. By default, the KOREAN_MORPH_LEXER
extracts all series of surrogate characters in a document as one token for each series.
Limitations on Korean Unicode Support
For conversion from Hanja to Hangul (Korean), the KOREAN_MORPH_LEXER
supports only the 4,888 Hanja characters defined in KSC5601.
2.5.8.3 KOREAN_MORPH_LEXER Attributes
When you use the KOREAN_MORPH_LEXER
, you can specify the following attributes:
Table 2-28 KOREAN_MORPH_LEXER Attributes
Attribute | Attribute Value |
---|---|
Specify |
|
Specify |
|
Specify |
|
Specify |
|
Specify |
|
Specify indexing style of composite noun. Specify Specify Specify "KOREAN_MORPH_LEXER Example: Setting Composite Attribute" describes the difference between |
|
Specify |
|
Specify |
|
Specify |
|
Specify |
|
Specify |
|
Specify |
2.5.8.4 KOREAN_MORPH_ LEXER Limitations
Sentence and paragraph sections are not supported with the KOREAN_MORPH_LEXER
.
2.5.8.5 KOREAN_MORPH_LEXER Example: Setting Composite Attribute
Use the composite attribute to control how composite nouns are indexed.
NGRAM Example
When you specify NGRAM
for the composite attribute, composite nouns are indexed with all possible component tokens. For example, the following composite noun (information processing institute)
is indexed as six tokens:
Specify NGRAM
indexing as follows:
begin ctx_ddl.create_preference('my_lexer','KOREAN_MORPH_LEXER'); ctx_ddl.set_attribute('my_lexer','COMPOSITE','NGRAM'); end
To create the index:
create index koreanx on korean(text) indextype is ctxsys.context parameters ('lexer my_lexer');
COMPONENT_WORD Example
When you specify COMPONENT_WORD
for the composite attribute, composite nouns and their components are indexed. For example, the following composite noun (information processing institute)
is indexed as four tokens:
Specify COMPONENT_WORD
indexing as follows:
begin ctx_ddl.create_preference('my_lexer','KOREAN_MORPH_LEXER'); ctx_ddl.set_attribute('my_lexer','COMPOSITE','COMPONENT_WORD'); end
To create the index:
create index koreanx on korean(text) indextype is ctxsys.context parameters ('lexer my_lexer');
2.5.9 USER_LEXER
Lexer you create to index a particular user-defined language.
Use USER_LEXER
to plug in your own language-specific lexing solution. This enables you to define lexers for languages that are not supported by Oracle Text. It also enables you to define a new lexer for a language that is supported but whose lexer is inappropriate for your application.
This section contains the following topics.
2.5.9.1 USER_LEXER Routines
The user-defined lexer you register with Oracle Text is composed of two routines that you must supply:
Table 2-29 User-Defined Routines for USER_LEXER
User-Defined Routine | Description |
---|---|
Indexing Procedure |
Stored procedure (PL/SQL) which implements the tokenization of documents and stop words. Output must be an XML document as specified in this section. |
Query Procedure |
Stored procedure (PL/SQL) which implements the tokenization of query words. Output must be an XML document as specified in this section. |
2.5.9.2 USER_LEXER Limitations
The following features are not supported with the USER_LEXER
:
-
CTX_DOC.GIST
andCTX_DOC.THEMES
-
CTX_QUERY.HFEEDBACK
-
ABOUT
query operator -
CTXRULE
index type -
VGRAM
indexing algorithm
2.5.9.3 USER_LEXER Attributes
USER_LEXER
has the following attributes:
Table 2-30 USER_LEXER Attributes
Attribute | Attribute Value |
---|---|
|
Name of a stored procedure. No default provided. |
|
|
|
Name of a stored procedure. No default provided. |
2.5.9.4 INDEX_PROCEDURE
This callback stored procedure is called by Oracle Text as needed to tokenize a document or a stop word found in the stoplist object.
Requirements
This procedure can be a PL/SQL stored procedure.
The index owner must have EXECUTE
privilege on this stored procedure.
This stored procedure must not be replaced or dropped after the index is created. You can replace or drop this stored procedure after the index is dropped.
Parameters
Two different interfaces are supported for the user-defined lexer indexing procedure:
Restrictions
This procedure must not perform any of the following operations:
-
Rollback
-
Explicitly or implicitly commit the current transaction
-
Enter any other transaction control statement
-
Alter the session language or territory
The child elements of the root element tokens of the XML document returned must be in the same order as the tokens occur in the document or stop word being tokenized.
The behavior of this stored procedure must be deterministic with respect to all parameters.
2.5.9.5 INPUT_TYPE
Two different interfaces are supported for the User-defined lexer indexing procedure. One interface enables the document or stop word and the corresponding tokens encoded as XML to be passed as VARCHAR2
datatype whereas the other interface uses the CLOB
datatype. This attribute indicates the interface implemented by the stored procedure specified by the INDEX_PROCEDURE
attribute.
2.5.9.5.1 VARCHAR2 Interface
Table 2-31 describes the interface that enables the document or stop word from stoplist object to be tokenized to be passed as VARCHAR2
from Oracle Text to the stored procedure and for the tokens to be passed as VARCHAR2
as well from the stored procedure back to Oracle Text.
Your user-defined lexer indexing procedure should use this interface when all documents in the column to be indexed are smaller than or equal to 32512 bytes and the tokens can be represented by less than or equal to 32512 bytes. In this case the CLOB
interface given in Table 2-32 can also be used, although the VARCHAR2
interface will generally perform faster than the CLOB
interface.
This procedure must be defined with the following parameters:
Table 2-31 VARCHAR2 Interface for INDEX_PROCEDURES
Parameter Position | Parameter Mode | Parameter Datatype | Description |
---|---|---|---|
1 |
|
|
Document or stop word from stoplist object to be tokenized. If the document is larger than 32512 bytes then Oracle Text will report a document level indexing error. |
2 |
|
|
Tokens encoded as XML. If the document contains no tokens, then either NULL must be returned or the tokens element in the XML document returned must contain no child elements. Byte length of the data must be less than or equal to 32512. To improve performance, use the The XML document returned by this procedure should not include unnecessary whitespace characters (typically used to improve readability). This reduces the size of the XML document which in turn minimizes the transfer time. To improve performance, index_procedure should not validate the XML document with the corresponding XML schema at run-time. Note that this parameter is |
3 |
|
|
Oracle Text sets this parameter to Oracle Text sets this parameter to |
2.5.9.5.2 CLOB Interface
Table 2-32 describes the CLOB
interface that enables the document or stop word from stoplist object to be tokenized to be passed as CLOB
from Oracle Text to the stored procedure and for the tokens to be passed as CLOB
as well from the stored procedure back to Oracle Text.
The user-defined lexer indexing procedure should use this interface when at least one of the documents in the column to be indexed is larger than 32512 bytes or the corresponding tokens are represented by more than 32512 bytes.
Table 2-32 CLOB Interface for INDEX_PROCEDURE
Parameter Position | Parameter Mode | Parameter Datatype | Description |
---|---|---|---|
1 |
|
|
Document or stop word from stoplist object to be tokenized. |
2 |
|
|
Tokens encoded as XML. If the document contains no tokens, then either NULL must be returned or the tokens element in the XML document returned must contain no child elements. To improve performance, use the The XML document returned by this procedure should not include unnecessary whitespace characters (typically used to improve readability). This reduces the size of the XML document which in turn minimizes the transfer time. To improve performance, index_procedure should not validate the XML document with the corresponding XML schema at run-time. Note that this parameter is |
3 |
|
|
Oracle Text sets this parameter to Oracle Text sets this parameter to |
The first and second parameters are temporary CLOBS
. Avoid assigning these CLOB
locators to other locator variables. Assigning the formal parameter CLOB
locator to another locator variable causes a new copy of the temporary CLOB
to be created resulting in a performance hit.
2.5.9.6 QUERY_PROCEDURE
This callback stored procedure is called by Oracle Text as needed to tokenize words in the query. A space-delimited group of characters (excluding the query operators) in the query will be identified by Oracle Text as a word.
Requirements
This procedure can be a PL/SQL stored procedure.
The index owner must have EXECUTE
privilege on this stored procedure.
This stored procedure must not be replaced or be dropped after the index is created. You can replace or drop this stored procedure after the index is dropped.
Restrictions
This procedure must not perform any of the following operations:
-
Rollback
-
Explicitly or implicitly commit the current transaction
-
Enter any other transaction control statement
-
Alter the session language or territory
The child elements of the root element tokens of the XML document returned must be in the same order as the tokens occur in the query word being tokenized.
The behavior of this stored procedure must be deterministic with respect to all parameters.
Parameters
Table 2-33 describes the interface for the user-defined lexer query procedure:
Table 2-33 User-defined Lexer Query Procedure XML Schema Attributes
Parameter Position | Parameter Mode | Parameter Datatype | Description |
---|---|---|---|
1 |
|
|
Query word to be tokenized. |
2 |
|
|
Character offsets of wildcard characters (% and _) in the query word. If the query word passed in by Oracle Text does not contain any wildcard characters then this index-by table will be empty. The wildcard characters in the query word must be preserved in the tokens returned in order for the wildcard query feature to work properly. The character offset is 0 (zero) based. Offset information follows USC-2 codepoint semantics. |
3 |
|
|
Tokens encoded as XML. If the query word contains no tokens then either NULL must be returned or the tokens element in the XML document returned must contain no child elements. The length of the data must be less-than or equal to 32512 bytes. |
2.5.9.7 Encoding Tokens as XML
The sequence of tokens returned by your stored procedure must be represented as an XML 1.0 document. The XML document must be valid with respect to the XML Schemas given in the following sections.
Limitations
To boost performance of this feature, the XML parser in Oracle Text will not perform validation and will not be a full-featured XML compliant parser. This implies that only minimal XML features will be supported. The following XML features are not supported:
-
Document Type Declaration (for example,
<!DOCTYPE [...]>
) and therefore entity declarations. Only the following built-in entities can be referenced: lt, gt, amp, quot, and apos. -
CDATA sections.
-
Comments.
-
Processing Instructions.
-
XML declaration (for example,
<?xml version="1.0" ...?>
). -
Namespaces.
-
Use of elements and attributes other than those defined by the corresponding XML Schema.
-
Character references (for example ট).
-
xml:space attribute.
-
xml:lang attribute
2.5.9.8 XML Schema for No-Location, User-defined Indexing Procedure
This section describes additional constraints imposed on the XML document returned by the user-defined lexer indexing procedure when the third parameter is FALSE
. The XML document returned must be valid with respect to the following XML Schema:
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"> <xsd:element name="tokens"> <xsd:complexType> <xsd:sequence> <xsd:choice minOccurs="0" maxOccurs="unbounded"> <xsd:element name="eos" type="EmptyTokenType"/> <xsd:element name="eop" type="EmptyTokenType"/> <xsd:element name="num" type="xsd:token"/> <xsd:group ref="IndexCompositeGroup"/> </xsd:choice> </xsd:sequence> </xsd:complexType> </xsd:element> <!-- Enforce constraint that compMem element must be preceded by word element or compMem element for indexing --> <xsd:group name="IndexCompositeGroup"> <xsd:sequence> <xsd:element name="word" type="xsd:token"/> <xsd:element name="compMem" type="xsd:token" minOccurs="0" maxOccurs="unbounded"/> </xsd:sequence> </xsd:group> <!-- EmptyTokenType defines an empty element without attributes --> <xsd:complexType name="EmptyTokenType"/> </xsd:schema>
Here are some of the constraints imposed by this XML Schema:
-
The root element is tokens. This is mandatory. It has no attributes.
-
The root element can have zero or more child elements. The child elements can be one of the following elements: eos, eop, num, word, and
compMem
. Each of these represent a specific type of token. -
The
compMem
element must be preceded by a word element or acompMem
element. -
The eos and eop elements have no attributes and must be empty elements.
-
The num, word, and
compMem
elements have no attributes. Oracle Text will normalize the content of these elements as follows: convert whitespace characters to space characters, collapse adjacent space characters to a single space character, remove leading and trailing spaces, perform entity reference replacement, and truncate to 255 bytes.
Table 2-34 describes the element names defined in the preceding XML Schema.
Table 2-34 User-defined Lexer Indexing Procedure XML Schema Element Names
Element | Description |
---|---|
word |
This element represents a simple word token. The content of the element is the word itself. Oracle Text does the work of identifying this token as being a stop word or non-stop word and processing it appropriately. |
num |
This element represents an arithmetic number token. The content of the element is the arithmetic number itself. Oracle Text treats this token as a stop word if the stoplist preference has Supporting this token type is optional. Without support for this token type, adding the |
eos |
This element represents end-of-sentence token. Oracle Text uses this information so that it can support Supporting this token type is optional. Without support for this token type, queries against the |
eop |
This element represents end-of-paragraph token. Oracle Text uses this information so that it can support Supporting this token type is optional. Without support for this token type, queries against the |
compMem |
Same as the word element, except that the implicit word offset is the same as the previous word token. Support for this token type is optional. |
Examples
Document: Vom Nordhauptbahnhof und aus der Innenstadt zum Messegelände.
Tokens:
<tokens> <word> VOM </word> <word> NORDHAUPTBAHNHOF </word> <compMem>NORD</compMem> <compMem>HAUPT </compMem> <compMem>BAHNHOF </compMem> <compMem>HAUPTBAHNHOF </compMem> <word> UND </word> <word> AUS </word> <word> DER </word> <word> INNENSTADT </word> <word> ZUM </word> <word> MESSEGELÄNDE </word> <eos/> </tokens>
Document: Oracle Database 11g Release 1
Tokens:
<tokens> <word> ORACLE11G</word> <word> RELEASE </word> <num> 1 </num> </tokens>
Document: WHERE salary<25000.00 AND job = 'F&B Manager'
Tokens:
<tokens> <word> WHERE </word> <word> salary<2500.00 </word> <word> AND </word> <word> job </word> <word> F&B </word> <word> Manager </word> </tokens>
2.5.9.9 XML Schema for User-defined Indexing Procedure with Location
This section describes additional constraints imposed on the XML document returned by the user-defined lexer indexing procedure when the third parameter is TRUE
. The XML document returned must be valid according to the following XML schema:
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"> <xsd:element name="tokens"> <xsd:complexType> <xsd:sequence> <xsd:choice minOccurs="0" maxOccurs="unbounded"> <xsd:element name="eos" type="EmptyTokenType"/> <xsd:element name="eop" type="EmptyTokenType"/> <xsd:element name="num" type="DocServiceTokenType"/> <xsd:group ref="DocServiceCompositeGroup"/> </xsd:choice> </xsd:sequence> </xsd:complexType> </xsd:element> <!-- Enforce constraint that compMem element must be preceeded by word element or compMem element for document service --> <xsd:group name="DocServiceCompositeGroup"> <xsd:sequence> <xsd:element name="word" type="DocServiceTokenType"/> <xsd:element name="compMem" type="DocServiceTokenType" minOccurs="0" maxOccurs="unbounded"/> </xsd:sequence> </xsd:group> <!-- EmptyTokenType defines an empty element without attributes --> <xsd:complexType name="EmptyTokenType"/> <!-- DocServiceTokenType defines an element with content and mandatory attributes --> <xsd:complexType name="DocServiceTokenType"> <xsd:simpleContent> <xsd:extension base="xsd:token"> <xsd:attribute name="off" type="OffsetType" use="required"/> <xsd:attribute name="len" type="xsd:unsignedShort" use="required"/> </xsd:extension> </xsd:simpleContent> </xsd:complexType> <xsd:simpleType name="OffsetType"> <xsd:restriction base="xsd:unsignedInt"> <xsd:maxInclusive value="2147483647"/> </xsd:restriction> </xsd:simpleType> </xsd:schema>
Some of the constraints imposed by this XML Schema are as follows:
-
The root element is tokens. This is mandatory. It has no attributes.
-
The root element can have zero or more child elements. The child elements can be one of the following elements: eos, eop, num, word, and
compMem
. Each of these represent a specific type of token. -
The
compMem
element must be preceded by a word element or acompMem
element. -
The eos and eop elements have no attributes and must be empty elements.
-
The num, word, and
compMem
elements have two mandatory attributes:off
and len. Oracle Text will normalize the content of these elements as follows: convert whitespace characters to space characters, collapse adjacent space characters to a single space character, remove leading and trailing spaces, perform entity reference replacement, and truncate to 255 bytes. -
The
off
attribute value must be an integer between 0 and 2147483647 inclusive. -
The
len
attribute value must be an integer between 0 and 65535 inclusive.
Table 2-34 describes the element types defined in the preceding XML Schema.
Table 2-35 describes the attributes defined in the preceding XML Schema.
Table 2-35 User-defined Lexer Indexing Procedure XML Schema Attributes
Attribute | Description |
---|---|
off |
This attribute represents the character offset of the token as it appears in the document being tokenized. The offset is with respect to the character document passed to the user-defined lexer indexing procedure, not the document fetched by the datastore. The document fetched by the datastore may be pre-processed by the filter object or the section group object, or both, before being passed to the user-defined lexer indexing procedure. The offset of the first character in the document being tokenized is 0 (zero). Offset information follows USC-2 codepoint semantics. |
len |
This attribute represents the character length (same semantics as SQL function The length is with respect to the character document passed to the user-defined lexer indexing procedure, not the document fetched by the datastore. The document fetched by the datastore may be pre-processed by the filter object or the section group object before being passed to the user-defined lexer indexing procedure. Length information follows USC-2 codepoint semantics. |
Sum of off
attribute value and len
attribute value must be less than or equal to the total number of characters in the document being tokenized. This is to ensure that the document offset and characters being referenced are within the document boundary.
Example
Document: User-defined Lexer.
Tokens:
<tokens> <word off="0" len="4"> USE </word> <word off="5" len="7"> DEF </word> <word off="13" len="5"> LEX </word> <eos/> </tokens>
2.5.9.10 XML Schema for User-defined Lexer Query Procedure
This section describes additional constraints imposed on the XML document returned by the user-defined lexer query procedure. The XML document returned must be valid with respect to the following XML Schema:
<xsd:schema xmlns:xsd="http://www.w3.org/2001/XMLSchema"> <xsd:element name="tokens"> <xsd:complexType> <xsd:sequence> <xsd:choice minOccurs="0" maxOccurs="unbounded"> <xsd:element name="num" type="QueryTokenType"/> <xsd:group ref="QueryCompositeGroup"/> </xsd:choice> </xsd:sequence> </xsd:complexType> </xsd:element> <!-- Enforce constraint that compMem element must be preceeded by word element or compMem element for query --> <xsd:group name="QueryCompositeGroup"> <xsd:sequence> <xsd:element name="word" type="QueryTokenType"/> <xsd:element name="compMem" type="QueryTokenType" minOccurs="0" maxOccurs="unbounded"/> </xsd:sequence> </xsd:group> <!-- QueryTokenType defines an element with content and with an optional attribute --> <xsd:complexType name="QueryTokenType"> <xsd:simpleContent> <xsd:extension base="xsd:token"> <xsd:attribute name="wildcard" type="WildcardType" use="optional"/> </xsd:extension> </xsd:simpleContent> </xsd:complexType> <xsd:simpleType name="WildcardType"> <xsd:restriction base="WildcardBaseType"> <xsd:minLength value="1"/> <xsd:maxLength value="64"/> </xsd:restriction> </xsd:simpleType> <xsd:simpleType name="WildcardBaseType"> <xsd:list> <xsd:simpleType> <xsd:restriction base="xsd:unsignedShort"> <xsd:maxInclusive value="378"/> </xsd:restriction> </xsd:simpleType> </xsd:list> </xsd:simpleType> </xsd:schema>
Here are some of the constraints imposed by this XML Schema:
-
The
root
element is tokens. This is mandatory. It has no attributes. -
The
root
element can have zero or more child elements. The child elements can be one of the following elements:num
andword
. Each of these represent a specific type of token. -
The
compMem
element must be preceded by aword
element or acompMem
element.The purpose of
compMem
is to enableUSER_LEXER
queries to return multiple forms for a single query. For example, if a user-defined lexer indexes the word bank asBANK(FINANCIAL)
andBANK(RIVER)
, the query procedure can return the first term as aword
and the second as acompMem
element:<tokens> <word>BANK(RIVER)</word> <compMem>BANK(FINANCIAL)</compMem> </tokens>
See Table 2-36, "Table 2-36" for more on the
compMem
element. -
The num and word elements have a single optional attribute: wildcard. Oracle Text will normalize the content of these elements as follows: convert whitespace characters to space characters, collapse adjacent space characters to a single space character, remove leading and trailing spaces, perform entity reference replacement, and truncate to 255 bytes.
-
The wildcard attribute value is a white-space separated list of integers. The minimum number of integers is 1 and the maximum number of integers is 64. The value of the integers must be between 0 and 378 inclusive. The intriguers in the list can be in any order.
Table 2-34 describes the element types defined in the preceding XML Schema.
Table 2-36 describes the attribute defined in the preceding XML Schema.
Table 2-36 User-defined Lexer Query Procedure XML Schema Attributes
Attribute | Description |
---|---|
|
Same as the |
|
Any The offset of the first character in the content of the element is 0. Offset information follows USC-2 codepoint semantics. If the token does not contain any wildcard characters then this attribute must not be specified. |
Examples
Query word: pseudo-%morph%
Tokens:
<tokens> <word> PSEUDO </word> <word wildcard="1 7"> %MORPH% </word> </tokens>
Query word: <%>
Tokens:
<tokens> <word wildcard="5"> <%> </word> </tokens>
2.5.10 WORLD_LEXER
A simple lexer that can index documents in any language or mixed languages. Works with short strings and long documents. Does not support stemming or other lexer-related attributes.
Use the WORLD_LEXER
to index text columns that contain documents of different languages. For example, use this lexer to index a text column that stores English, Japanese, and German documents.
WORLD_LEXER
differs from MULTI_LEXER
in that WORLD_LEXER
automatically detects the language(s) of a document. Unlike MULTI_LEXER
, WORLD_LEXER
does not require you to have a language column in your base table nor to specify the language column when you create the index. Moreover, it is not necessary to use sub-lexers, as with MULTI_LEXER
. (See "MULTI_LEXER".)
WORLD_LEXER
supports all database character sets, and for languages whose character sets are Unicode-based, it supports the Unicode 5.0 standard. For a list of languages that WORLD_LEXER
can work with, see "World Lexer Features".
The WORLD_LEXER
has the following attributes:
Table 2-37 WORLD_LEXER Attributes
Attribute | Attribute Value |
---|---|
|
Enables mixed-case (upper- and lower-case) searches of text (for example, cat and Cat). Allowable values are |
|
Specify the non alphanumeric characters that, when they appear anywhere in a word (beginning, middle, or end), are processed as alphanumeric and included with the token in the Text index. This includes printjoins that occur consecutively. See Basic Lexer ""printjoins"". |
|
Specify the non-alphanumeric characters that, when they appear within a word, identify the word as a single token; however, the characters are not stored with the token in the Text index. See Basic Lexer ""skipjoins"". |
Rules for PRINTJOIN and SKIPJOIN Characters
Refer to ”Rules for PRINTJOIN and SKIPJOIN Characters” in JAPANESE_VGRAM_LEXER.
WORLD_LEXER Example
The following is an example of creating an index using WORLD_LEXER
.
exec ctx_ddl.create_preference('MYLEXER', 'world_lexer'); create index doc_idx on doc(data) indextype is CONTEXT parameters ('lexer MYLEXER stoplist CTXSYS.EMPTY_STOPLIST');
2.6 Wordlist Type
Use the wordlist preference to enable the query options such as stemming, fuzzy matching for your language. You can also use the wordlist preference to enable substring and prefix indexing, which improves performance for wildcard queries with CONTAINS
and CATSEARCH
.
To create a wordlist preference, you must use BASIC_WORDLIST
, which is the only type available.
2.6.1 BASIC_WORDLIST
Use BASIC_WORDLIST
type to enable stemming and fuzzy matching or to create prefix indexes with Text indexes.
Table 2-38 BASIC_WORDLIST Attributes
- stemmer
-
Specify the stemmer used for word stemming in Text queries. When you do not specify a value for
STEMMER
, the default isENGLISH
.Specify
AUTO
for the system to automatically set the stemming language according to the language setting of the database session. If the database language isAMERICAN
orENGLISH
, then theENGLISH
stemmer is automatically used. Otherwise, the stemmer that maps to the database session language is used.When there is no stemmer for a language, the default is
NULL
. With theNULL
stemmer, the stem operator is ignored in queries.You can create your own stemming user-dictionary. See "Stemming User-Dictionaries" for more information.
Note:
The
STEMMER
attribute ofBASIC_WORDLIST
preference will be ignored if:-
INDEX_STEMS
attribute ofBASIC_LEXER
preference is set toBOKMAL
,CATALAN
,CROATIAN
,CZECH
,DANISH
,FINNISH
,GREEK
,HEBREW
,HUNGARIAN
,NYNORSK
,POLISH
,PORTUGUESE
,ROMANIAN
,RUSSIAN
,SERBIAN
,SLOVAK
,SLOVENIAN
,SWEDISH
,ENGLISH_NEW
,DERIVATIONAL_NEW
,DUTCH_NEW
,FRENCH_NEW
,GERMAN_NEW
,ITALIAN_NEW
, orSPANISH_NEW
.Or
-
INDEX_STEMS
attribute ofAUTO_LEXER
preference is set toYES
.Or
-
The database session language causes
MULTI_LEXER
to choose aSUB_LEXER
with the same setting as 1 or 2 above.
In these cases, the same stemmer that is used by the
BASIC_LEXER
orAUTO_LEXER
during indexing will be used to determine the stem of the query term during query. -
- fuzzy_match
-
Specify which fuzzy matching routines are used for the column. Fuzzy matching is currently supported for English, Japanese, and, to a lesser extent, the Western European languages.
Note:
The
fuzzy_match
attributes value for Chinese and Korean are dummy attribute values that prevent the English and Japanese fuzzy matching routines from being used on Chinese and Korean text.The default for
fuzzy_match
isGENERIC
.Specify
AUTO
for the system to automatically set the fuzzy matching language according to language setting of the session.
- fuzzy_score
-
Specify a default lower limit of fuzzy score. Specify a number between 1 and 80. Text with scores below this number are not returned. The default is 60.
Fuzzy score is a measure of how close the expanded word is to the query word. The higher the score the better the match. Use this parameter to limit fuzzy expansions to the best matches.
- fuzzy_numresults
-
Specify the maximum number of fuzzy expansions. Use a number between 0 and 5000. The default is 100.
Setting a fuzzy expansion limits the expansion to a specified number of the best matching words.
- substring_index
-
Specify
TRUE
for Oracle Text to create a substring index. A substring index improves performance for left-truncated or double-truncated wildcard queries such as %ing or %benz%. The default is false.Limitations of
substring_index
:Oracle recommends using the
wildcard_index
attribute oversubstring_index
. See "wildcard_index". Substring indexing has the following impact on indexing and disk resources:-
Index creation and DML processing is up to 4 times slower.
-
Index creation with
substring_index
enabled requires more rollback segments during index flushes than withsubstring_index
off. Do either of the following when creating a substring index:-
Make available double the usual rollback.
-
Decrease the index memory to reduce the size of the index flushes to disk.
-
-
- prefix_index
-
Specify
yes
to enable prefix indexing. Prefix indexing improves performance for right truncated wildcard searches such as TO%. Default isNO
.Note:
Enabling prefix indexing increases index size.
Prefix indexing chops up tokens into multiple prefixes to store in the $I table. For example, words
TOKEN
andTOY
are normally indexed as follows in the $I table:Token Type Information TOKEN
0
DOCID 1 POS 1
TOY
0
DOCID 1 POS 3
With prefix indexing, Oracle Text indexes the prefix substrings of these tokens as follows with a new token type of 6:
Token Type Information TOKEN
0
DOCID 1 POS 1
TOY
0
DOCID 1 POS 3
T
6
DOCID 1 POS 1 POS 3
TO
6
DOCID 1 POS 1 POS 3
TOK
6
DOCID 1 POS 1
TOKE
6
DOCID 1 POS 1
TOKEN
6
DOCID 1 POS 1
TOY
6
DOCID 1 POS 3
Wildcard searches such as
TO%
are now faster because Oracle Text does no expansion of terms and merging of result sets. To obtain the result, Oracle Text need only examine the (TO,6) row. - prefix_min_length
-
Specify the minimum length of indexed prefixes. Default is 1.
For example, setting
prefix_min_length
to 3 andprefix_max_length
to 5 indexes all prefixes between 3 and 5 characters long.Note:
A wildcard search whose pattern is below the minimum length or above the maximum length is searched using the slower method of equivalence expansion and merging.
- prefix_max_length
-
Specify the maximum length of indexed prefixes. Default is 64.
For example, setting
prefix_min_length
to 3 andprefix_max_length
to 5 indexes all prefixes between 3 and 5 characters long.Note:
A wildcard search whose pattern is below the minimum length or above the maximum length is searched using the slower method of equivalence expansion and merging.
- wildcard_maxterms
-
Specify the maximum number of terms in a wildcard (%) expansion. Use this parameter to keep wildcard query performance within an acceptable limit. When the wildcard query expansion exceeds this number, Oracle Text returns the following error:
ORA-29902: error in executing ODCIIndexStart() routine ORA-20000: Oracle Text error: DRG-51030: wildcard query expansion resulted in too many terms
In such cases, use a more restrictive query so that it results in fewer matches or increase the value of
wildcard_maxterms
. You can also setwildcard_maxterms
to 0 to ignore the limit.Note:
If the value of
wildcard_maxterms
is set as 0, the query might fail and returns the above error again if too many terms are matched by the wildcard search term.You can also capture the above error and display your own less terse message.
Note:
Search terms with wildcard queries having only the wildcard character, for example:
%
,%_%
, and%_
, are threaded as stopwords.Note:
wildcard_maxterms
is independent of the newWILDCARD_INDEX
option.wildcard_maxterms
can be set even ifWILDCARD_INDEX
is not used. - ndata_base_letter
-
Specify whether characters that have diacritical marks (umlauts, cedillas, acute accents, and so on) are converted to their base form before being stored in the Text index or queried by the
NDATA
operator. The default isFALSE
(base-letter conversion disabled). For more information on base-letter conversions, see "Base-Letter Conversion". - ndata_alternate_spelling
-
Specify whether to enable alternate spelling for German, Danish, and Swedish. Enabling alternate spelling allows you to index
NDATA
section data and query using theNDATA
operator in alternate form.When
ndata_base_letter
is enabled at the same time asndata_alternate_spelling
,NDATA
section data is serially transformed first by alternate spelling and then by base lettering. For more information about the alternate spelling conventions Oracle Text uses, see "Alternate Spelling". - ndata_thesaurus
-
Specify a name of the thesaurus used for alternate name expansion. The indexing engine expands names in documents using synonym rings in the thesaurus. A user should make use of homographic disambiguating feature of the thesaurus to distinguish common nicknames.
An example is:
Albert SYN Al SYN Bert Alfred SYN Al SYN Fred
A simple definition such as the above will put Albert, Alfred, Al, Bert, and Fred into the same synonym ring. This will cause an unexpected expansion such that the expansion of Bert includes Fred. To prevent this, you can use homographic disambiguation as in:
Albert SYN Al (Albert) SYN Bert (Albert) Alfred SYN Al (Alfred) SYN Fred (Alfred)
This forms two synonym rings, Albert-Al-Bert and Alfred-Al-Fred. Thus, the expansion of Bert no longer includes Fred. A more detailed example is:
begin ctx_ddl.create_preference('NDAT_PREF', 'BASIC_WORDLIST'); ctx_ddl.set_attribute('NDATA_PREF', 'NDATA_ALTERNATE_SPELLING', 'FALSE'); ctx_ddl.set_attribute('NDATA_PREF', 'NDATA_BASE_LETTER', 'TRUE'); ctx_ddl.set_attribute('NDATA_PREF', 'NDATA_THESAURUS', 'NICKNAMES'); end;
Note:
A sample thesaurus for names can be found in the
$ORACLE_HOME/ctx/sample/thes
directory. This file isdr0thsnames.txt
. - ndata_join_particles
-
Specify a list of colon-separated name particles that can be joined with a name that follows them. A name particle, such as da, is written separately from or joined with its following name like da Vinci or daVinci. The indexing engine generates index data for both separated and join versions of a name when it finds a name particle specified in this preference. The same happens in the query processing for better recall.
- reverse_index
-
Reverse index allows for fast searches on left-truncated search terms.
Indexed words are stored in the token table
($I)
which has an index($X)
on it. Normally, if a search term such as “%xxx” is used in a query, the$X
index cannot be used. So, a full table scan of the$I
table is necessary, which can lead to poor search performance.Setting
REVERSE_INDEX
toTRUE
creates an extra index($V)
on a reverse form of the tokens. This allows for indexed lookups for left-truncated terms, leading to much better query performance for such terms.REVERSE_INDEX
speeds up searching of tokens with leading wildcards such as the second word in the search "oracle %base". If the token has both leading and trailing wildcards such as "oracle %bas%" this attribute will not help and theSUBSTRING_INDEX
option should be used instead.Specify the attribute as a part of the wordlist preference and set it to
TRUE
orFALSE
. Default isFALSE
. Set this attribute usingCTX_DDL.SET_ATTRIBUTE
procedure or usingALTER INDEX REBUILD
statement as used in any wordlist preference.Syntax
ctx_ddl.set_attribute(worlist_pref_name, 'REVERSE_INDEX', BOOLEAN);
- worlist_pref_name
- Specify the first argument as the wordlist preference name.
- REVERSE_INDEX
- Specify the wordlist preference name as
REVERSE_INDEX
. - BOOLEAN
- The attribute can be set to
TRUE
orFALSE
. By default, the value isFALSE
.
The following example creates a wordlist preference and sets
REVERSE_INDEX
toTRUE
:exec ctx_ddl.create_preference(‘wrdlst’, ‘BASIC_WORDLIST’); exec ctx_ddl.set_attribute(‘wrdlst’, ‘REVERSE_INDEX’, ‘TRUE’);
The following traces are added for the Reverse Index
$V
which can be used to track timing and usage of this index at query time.Trace ID Trace Name Description 37 TRACE_QRY_VV_TIME Time spent in executing the $V cursor 38 TRACE_QRY_VF_TIME Time spent in fetching rows from $V 39 TRACE_QRY_V_ROWS Number of rows with $V fetched metadata - wildcard_index
-
Wildcard indexing supports fast and efficient wildcard search for all wildcard expressions. It is set using
CTX_DDL.SET_ATTRIBUTE
procedure.Setting the
WILDCARD_INDEX
toTRUE
enables wildcard indexing.Syntax
ctx_ddl.set_attribute(<wordlist_pref_name>, 'WILDCARD_INDEX', BOOLEAN);
- wordlist_pref_name
- Specify the first argument as the wordlist preference name.
- WILDCARD_INDEX
- Specify the wordlist preference name as
WILDCARD_INDEX
. - BOOLEAN
- The attribute can be set to
TRUE
orFALSE
.
The following example creates a wordlist preference and sets
WILDCARD_INDEX
toTRUE
:begin ctx_ddl.create_preference('mywordlist','BASIC_WORDLIST'); ctx_ddl.set_attribute('mywordlist','WILDCARD_INDEX','TRUE'); end;
Optimization of Wildcard Index
WILDCARD_INDEX
can be optimized either as part of full optimize or as part of section type optimize.The following two examples are ways of optimizing a wildcard index:
begin ctx_ddl.optimize_index('idx','FULL'); end; begin ctx_ddl.optimize_index('idx','TOKEN_TYPE',section_type=>CTX_DDL.SECTION_WILDCARD_INDEX); end;
Note:
Wildcard indexing is supported for languages which only use single-byte characters.
- wildcard_index_k
-
The
WILDCARD_INDEX
uses a technology known as K-grams (fixed-length substring particles).WILDCARD_INDEX_K
defines the size of these grams (K). The value can range between2
and5
. The default value is3
. Set this attribute usingCTX_DDL.SET_ATTRIBUTE
procedure or usingALTER INDEX REBUILD
statement as used in any wordlist preference.Note:
WILDCARD_INDEX
must be set toTRUE
before settingWILDCARD_INDEX_K
.The following are some considerations before changing the value of K from the default value of 3:
-
Query terms that are shorter than the value of K cannot be retrieved using K-gram indexing.
-
Decreasing the value of K increases the storage requirements and increasing the value of K decreases the storage requirements.
-
Wildcard query terms must have at least K consecutive non-wildcard characters to use K-gram indexing. For example, if K value is 3, queries like “%abc%” or “%abcd%” can use K-gram indexing. For the same K value, queries like “%ab%” cannot use K-gram indexing.
-
Wildcard query terms having at least K-1 consecutive non-wildcard characters at the beginning or end of the query term, can use K-gram indexing. For example, if K value is 3, queries like “ab%” and “%ab” can use k-gram indexing.
The following example creates a wordlist preference and enables K-gram indexing with a K value of
4
:begin ctx_ddl.create_preference('mywordlist','BASIC_WORDLIST'); ctx_ddl.set_attribute('mywordlist','WILDCARD_INDEX','TRUE'); ctx_ddl.set_attribute('mywordlist','WILDCARD_INDEX_K',4); end;
-
Related Topics
2.6.2 BASIC_WORDLIST Example
The following example shows the use of the BASIC_WORDLIST
type.
2.6.2.1 Enabling Fuzzy Matching and Stemming
The following example enables stemming and fuzzy matching for English. The preference STEM_FUZZY_PREF
sets the number of expansions to the maximum allowed. This preference also instructs the system to create a substring index to improve the performance of double-truncated searches.
begin ctx_ddl.create_preference('STEM_FUZZY_PREF', 'BASIC_WORDLIST'); ctx_ddl.set_attribute('STEM_FUZZY_PREF','FUZZY_MATCH','ENGLISH'); ctx_ddl.set_attribute('STEM_FUZZY_PREF','FUZZY_SCORE','1'); ctx_ddl.set_attribute('STEM_FUZZY_PREF','FUZZY_NUMRESULTS','5000'); ctx_ddl.set_attribute('STEM_FUZZY_PREF','SUBSTRING_INDEX','TRUE'); ctx_ddl.set_attribute('STEM_FUZZY_PREF','STEMMER','ENGLISH'); end;
To create the index in SQL, enter the following statement:
create index fuzzy_stem_subst_idx on mytable ( docs ) indextype is ctxsys.context parameters ('Wordlist STEM_FUZZY_PREF');
2.6.2.2 Enabling Sub-string and Prefix Indexing
The following example sets the wordlist preference for prefix and sub-string indexing. For prefix indexing, it specifies that Oracle Text create token prefixes between 3 and 4 characters long:
begin
ctx_ddl.create_preference('mywordlist', 'BASIC_WORDLIST'); ctx_ddl.set_attribute('mywordlist','PREFIX_INDEX','TRUE'); ctx_ddl.set_attribute('mywordlist','PREFIX_MIN_LENGTH',3); ctx_ddl.set_attribute('mywordlist','PREFIX_MAX_LENGTH', 4); ctx_ddl.set_attribute('mywordlist','SUBSTRING_INDEX', 'YES');
end;
2.6.2.3 Setting Wildcard Expansion Limit
Use the wildcard_maxterms attribute to set the maximum allowed terms in a wildcard expansion.
--- create a sample table drop table quick ; create table quick ( quick_id number primary key, text varchar(80) ); --- insert a row with 10 expansions for 'tire%' insert into quick ( quick_id, text ) values ( 1, 'tire tirea tireb tirec tired tiree tiref tireg tireh tirei tirej'); commit; --- create an index using wildcard_maxterms=100 begin Ctx_Ddl.Create_Preference('wildcard_pref', 'BASIC_WORDLIST'); ctx_ddl.set_attribute('wildcard_pref', 'wildcard_maxterms', 100) ; end; / create index wildcard_idx on quick(text) indextype is ctxsys.context parameters ('Wordlist wildcard_pref') ; --- query on 'tire%' - should work fine select quick_id from quick where contains ( text, 'tire%' ) > 0; --- now re-create the index with wildcard_maxterms=5 drop index wildcard_idx ; begin Ctx_Ddl.Drop_Preference('wildcard_pref'); Ctx_Ddl.Create_Preference('wildcard_pref', 'BASIC_WORDLIST'); ctx_ddl.set_attribute('wildcard_pref', 'wildcard_maxterms', 5) ; end; / create index wildcard_idx on quick(text) indextype is ctxsys.context parameters ('Wordlist wildcard_pref') ; --- query on 'tire%' gives "wildcard query expansion resulted in too many terms" select quick_id from quick where contains ( text, 'tire%' ) > 0;
2.7 Storage Types
Use the storage preference to specify tablespace and creation parameters for tables associated with a Text index. The system provides a single storage type called BASIC_STORAGE
:
Table 2-39 Storage Types
Type | Description |
---|---|
Indexing type used to specify the tablespace and creation parameters for the database tables and indexes that constitute a Text index. |
2.7.1 BASIC_STORAGE
The BASIC_STORAGE
indexing type specifies the tablespace and creation parameters for the database tables and indexes that constitute a Text index.
The clause you specify is added to the internal CREATE
TABLE
(CREATE
INDEX
for the i_index_clause
) statement at index creation. You can specify most allowable clauses, such as storage, LOB storage, or partitioning. However, you cannot specify an index organized table clause.
You can store Text index tables in the In-Memory Column Store (IM column store) by specifying inmemory
in the storage clause for that table. IM column store is supported for the types of tables represented by the following storage attributes: I_TABLE_CLAUSE
, R_TABLE_CLAUSE
, G_TABLE_CLAUSE
, O_TABLE_CLAUSE
, D_TABLE_CLAUSE
, SN_TABLE_CLAUSE
, and E_TABLE_CLAUSE
.
This section contains the following topics.
See Also:
-
Oracle Database SQL Language Reference for more information about how to specify
CREATE
INDEX
statement -
Oracle Database SQL Language Reference for more information about how to specify
CREATE
TABLE
statement
2.7.1.1 BASIC_STORAGE Attributes
The BASIC_STORAGE
indexing type supports these attributes for database tables and indexes.
For search indexes, user-specific partitioning clauses are not supported with all the table and index clauses because these indexes use system-managed partitioning.
Table 2-40 BASIC_STORAGE Attributes
Attribute | Attribute Value |
---|---|
|
Parameter clause to improve the query performance for the There is not much of a query performance improvement when the data storage is on solid state disks. Set it to Note:
|
|
Parameter clause to specify the storage clause for the $C table. Specify the storage and tablespace clauses to add to the end of the internal The functionality of the $C table takes the place of the previously shared CTXSYS.DR$PENDING table. |
|
Parameter clause to specify the storage clause for the $D table. This clause may be specified if the forward index feature is being used. The forward index feature is used to increase the query performance while calculating snippets. If the The $D table is created to save a copy of a document into the index by either specifying a |
|
Parameter clause to improve the performance of the following
Set it to TRUE to enable the forward index feature. This creates the $O table. The $O table stores the mapping information from the token offsets in the $I table to character offsets in the indexed documents. The default is FALSE. |
|
Parameter clause for the $H btree index on the $G table. Specify the storage and tablespace clauses to add to the end of the internal When a CONTEXT index is created with the STAGE_ITAB index option, an empty $G table is created with the $H btree index on it. Use the |
|
Parameter clause for the $G table. Specify the storage and tablespace clauses to add to the end of the internal When a CONTEXT index is created with the STAGE_ITAB index option, an empty $G table is created with the $H btree index on it. Use the |
Parameter clause for dr$indexname$X index creation. Specify storage and tablespace clauses to add to the end of the internal If you choose to override the default, Oracle recommends including |
|
|
Parameter clause to specify the storage clause for the $R index on dr$rowid column of the $I table. Specify storage and tablespace clauses to add to the end of the internal This clause is only used by the |
Parameter clause for dr$indexname$I table creation. Specify storage and tablespace clauses to add to the end of the internal The I table is the index data table. Note: Oracle strongly recommends that you do not specify "disable storage in row" for $I LOBs, as this greatly degrades the query performance. |
|
Parameter clause for dr$indexname$K table creation. Specify storage and tablespace clauses to add to the end of the internal The K table is the keymap table. |
|
Parameter clause for $KG table creation. Specify storage and tablespace clauses to add to the end of the internal The KG table stores the k-gram index to facilitate efficient wildcard search. |
|
Parameter clause for $KGI index creation. Specify storage and tablespace clauses to add to the end of the internal |
|
Parameter clause for dr$indexname$N table creation. Specify storage and tablespace clauses to add to the end of the internal The $N table is the negative list table which keeps track of deleted document IDs. These document IDs must be cleaned up by index optimization. |
|
|
Parameter clause to specify the storage clause for the $O table. This clause may be specified if the forward index feature is being used. The forward index feature is used to increase the query performance while calculating snippets. If the The $O table is created when the forward index feature is enabled by specifying the |
Parameter clause for the substring index if you have enabled Specify storage and tablespace clauses to add to the end of the internal |
|
|
Parameter clause to specify the storage clause for the $Q table. Specify the storage and tablespace clauses to add to the end of the internal The functionality of the $Q table takes the place of the previously shared |
Parameter clause to specify the maximum size of the query filter cache in bytes. The query filter cache is allocated out of the shared pool, so its maximum size must be smaller than the shared pool size. When this storage preference is set at the partition level, it is implicitly set at the index level. The default is Note: Starting in Oracle Database Release 21c,
|
|
Parameter clause for The The default clause is: If you modify this attribute, always include this clause for good performance. Note: When you set the |
|
|
Parameter clause for * For performance reasons, $S table must be created on a tablespace with db block size >= 4K without overflow segment and without a The S table is the table that stores If this clause is specified for a storage preference in an index without |
|
Parameter clause to specify saving the document to the Specify this clause to use the forward index feature for increasing the query performance while calculating snippets. Set it to Set it to The default is |
|
Parameter clause to specify the maximum size of a document to save in the If the document size is greater than the size specified in this attribute, the truncated version of the document having the size specified in this attribute is saved in the If the The default is 0, and the whole document is saved in the Note: The |
|
Parameter clause to improve the query performance for the Set it to Note: The |
|
Storage option for better performance if all the indexed data that is known in advance is single-byte. When set to |
|
Storage attribute to reduce the size of $R row. It improves DML and query performance during parallel DML and query workload. It reduces lock contention during DMLs, thus improving the DML performance. |
|
Parameter clause for |
|
Parameter clause for |
|
Parameter clause for |
|
Parameter clause for |
|
Parameter clause for |
|
Parameter clause for |
|
Parameter clause for |
|
Parameter clause for |
|
Parameter clause for |
|
Parameter clause for |
|
Parameter clause for |
|
Parameter clause for |
|
Parameter clause for |
|
Parameter clause for |
|
Parameter clause for |
|
Parameter clause for |
|
Parameter clause for |
|
Parameter clause for |
|
Parameter clause for |
|
Parameter clause for |
|
Switch to improve the query performance for the When the When the When the Set |
|
New storage option to enable automatic background optimize merge. Setting |
|
Storage option to ensure that the $G ( When the number of rows in the $G table exceeds this setting, a process is started to move all data from the $G table to the $I table, optimizing the data as it is moved. Note that this may cause certain SYNC operations or commits if SYNC(ON COMMIT) is used to take an unexpectedly long time because they may be moving many $G rows which have been inserted by other processes. If this is unacceptable, set When scheduling an auto optimization job, set If You can set If you set the value to 0 the automatic background merge is turned off. In this case, you must manually run With |
stage_itab_parallel |
New storage option controls the degree of parallelism used to merge rows from the The default value is 16 for the degree of parallelism. |
|
Specify the storage and tablespace clauses to add at the end of the internal |
Related Topics
2.7.1.2 BASIC_STORAGE Default Behavior
By default, BASIC_STORAGE
attributes are not set. In such cases, the Text index tables are created in the index owner's default tablespace. Consider the following statement, entered by user IUSER
, with no BASIC_STORAGE
attributes set:
create index IOWNER.idx on TOWNER.tab(b) indextype is ctxsys.context;
In this example, the text index is created in IOWNER's
default tablespace.
2.7.1.3 BASIC_STORAGE Examples
The following examples specify that the index tables are to be created in the foo
tablespace with an initial extent of 1K:
begin ctx_ddl.create_preference('mystore', 'BASIC_STORAGE'); ctx_ddl.set_attribute('mystore', 'I_TABLE_CLAUSE', 'tablespace foo storage (initial 1K)'); ctx_ddl.set_attribute('mystore', 'K_TABLE_CLAUSE', 'tablespace foo storage (initial 1K)'); ctx_ddl.set_attribute('mystore', 'R_TABLE_CLAUSE', 'tablespace users storage (initial 1K) lob (data) store as (disable storage in row cache)'); ctx_ddl.set_attribute('mystore', 'N_TABLE_CLAUSE', 'tablespace foo storage (initial 1K)'); ctx_ddl.set_attribute('mystore', 'I_INDEX_CLAUSE', 'tablespace foo storage (initial 1K) compress 2'); ctx_ddl.set_attribute('mystore', 'P_TABLE_CLAUSE', 'tablespace foo storage (initial 1K)'); ctx_ddl.set_attribute('mystore', 'S_TABLE_CLAUSE', 'tablespace foo storage (initial 1K)'); ctx_ddl.set_attribute('mystore', 'U_TABLE_CLAUSE', 'tablespace foo storage (initial 1K)');end;
The following example adds to the end of the internal table that is created.
exec ctx_ddl.create_preference('sto', 'basic_storage'); exec ctx_ddl.set_attribute('sto', 'e_table_clause', 'tablespace foo');
The following example uses query_filter_cache_size
storage parameter for a partitioned index:
exec ctx_ddl.create_preference('fcs', 'basic_storage'); exec ctx_ddl.set_attribute('fcs', 'query_filter_cache_size', '100000000'); create table fc(id number primary key, txt varchar2(255)) partition by range (id) ( partition p1 values less than (25), partition p2 values less than (50), partition p3 values less than (75) ); create index fci on fc(txt) indextype is ctxsys.context local ( partition p1, partition p2, partition p3) parameters('storage fcs memory 49M sync (on commit)');
The query filter cache is an index level storage preference. The storage preference for the query filter cache can be set at partition level only if this is also set at the index level.
select count(*) from fc partition (p1) where contains(txt,'ctxfiltercache((hello))')>0;
Note:
Starting in Oracle Database Release 21c,
CTXFILTERCACHE
is deprecated, and also
CTX_FILTER_CACHE_STATISTICS
and
QUERY_FILTER_CACHE_SIZE
.
SINGLE_BYTE Data Indexing Storage Attribute
Syntax
ctx_ddl.set_attribute(storage_pref_name, 'SINGLE_BYTE', BOOLEAN);
- storage_pref_name
- Specify the first argument as the storage preference name.
- SINGLE_BYTE
- Specify the storage attribute name as
SINGLE_BYTE
orsingle_byte
. - BOOLEAN
- Indicate whether the attribute is set. By default, the value is
FALSE
. It implies that the database character set identifies whether the documents are stored as single-byte or multi-byte.
The following example sets the storage preference and enables the single_byte
storage attribute:
exec ctx_ddl.create_preference('mysto', 'basic_storage'); ctx_ddl.set_attribute('mysto', 'single_byte', 'TRUE');
SMALL_R_ROW Storage Attribute
Syntax
ctx_ddl.set_attribute(storage_pref_name, 'SMALL_R_ROW', BOOLEAN);
- storage_pref_name
- Specify the first argument as the storage preference name.
- SMALL_R_ROW
- Specify the storage attribute name as
SMALL_R_ROW
orsmall_r_row
.. - BOOLEAN
- Indicate whether the attribute is set. By default, the value is
TRUE
.
The following example sets the storage preference and enables the small_r_row
storage attribute:
begin ctx_ddl.create_preference('sto', 'basic_storage'); ctx_ddl.set_attribute('sto', 'small_r_row', 'T', end;
To enable or disablesmall_r_row
feature on an existing index:
ALTER INDEX index_name rebuild PARAMETERS('replace storage sto');
By default, small_r_row=TRUE
, however, for earlier releases, small_r_row=FALSE.
2.8 Section Group Types
To enter WITHIN
queries on document sections, you must create a section group before you define your sections. Specify your section group in the parameter clause of CREATE INDEX.
This section contains the following topics.
2.8.1 Section Group Types for Creating a Section Group
To create a section group, you can specify one of the following group types with the CTX_DDL.CREATE_SECTION_GROUP procedure.
Table 2-41 Section Group Types
Type | Description |
---|---|
|
Use this group type when you define no sections or when you define only |
|
Use this group type for defining sections where the start and end tags are of the form Note: This group type does not support input such as unbalanced parentheses, comments tags, and attributes. Use |
|
Use this group type for indexing HTML documents and for defining sections in HTML documents. |
Use this group to create a JSON enabled context index. The |
|
|
Use this group type for indexing XML documents and for defining sections in XML documents. All sections to be indexed must be manually defined for this group. |
|
Use this group type to automatically create a zone section for each start-tag/end-tag pair in an XML document. The section names derived from XML tags are case sensitive as in XML. Attribute sections are created automatically for XML tags that have attributes. Attribute sections are named in the form tag@attribute. Special sections can be added to Stop sections, empty tags, processing instructions, and comments are not indexed. The following limitations apply to automatic section groups:
|
|
Use this group type to index XML documents. Behaves like the The difference is that with this section group you can do path searching with the |
|
Use this group for defining sections in newsgroup formatted documents according to RFC 1036. |
Note:
Starting with Oracle Database 18c, use ofNEWS_SECTION_GROUP
is deprecated in Oracle Text. Use external processing instead. If you want to index USENET posts, then preprocess the posts to use BASIC_SECTION_GROUP
or HTML_SECTION_GROUP
within Oracle Text. USENET is rarely used commercially.
2.8.2 Section Group Examples for HTML, XML, and JSON Enabled Documents
The examples show the use of section groups in HTML and XML documents, and in JSON enabled documents. See Table 2-41 for a summary.
This section contains the following examples:
2.8.2.1 Creating Section Groups in HTML Documents
The following statement creates a section group called htmgroup
with the HTML group type.
begin ctx_ddl.create_section_group('htmgroup', 'HTML_SECTION_GROUP'); end;
You can optionally add sections to this group using the procedures in the CTX_DDL
package, such as CTX_DDL.ADD_SPECIAL_SECTION
or CTX_DDL.ADD_ZONE_SECTION
. To index your documents, enter a statement such as:
create index myindex on docs(htmlfile) indextype is ctxsys.context parameters('filter ctxsys.null_filter section group htmgroup');
See Also:
For more information on section groups, see CTX_DDL Package
2.8.2.2 Creating Sections Groups in XML Documents
The following statement creates a section group called xmlgroup
with the XML_SECTION_GROUP
group type.
begin ctx_ddl.create_section_group('xmlgroup', 'XML_SECTION_GROUP'); end;
You can optionally add sections to this group using the procedures in the CTX_DDL
package, such as CTX_DDL.ADD_ATTR_SECTION
or CTX_DDL.ADD_STOP_SECTION
. To index your documents, enter a statement such as:
create index myindex on docs(htmlfile) indextype is ctxsys.context parameters('filter ctxsys.null_filter section group xmlgroup');
See Also:
For more information on section groups, see CTX_DDL Package
2.8.2.3 Automatic Sectioning in XML Documents
The following statement creates a section group called auto
with the AUTO_SECTION_GROUP
group type. This section group automatically creates sections from tags in XML documents.
begin
ctx_ddl.create_section_group('auto', 'AUTO_SECTION_GROUP');
end; CREATE INDEX myindex on docs(htmlfile) INDEXTYPE IS ctxsys.context PARAMETERS('filter ctxsys.null_filter section group auto');
2.8.2.4 Creating JSON Section Groups for JSON Search Index
The following example creates a JSON enabled text index.
create index json_ctx_idx on customers (customer _info) indextype is ctxsys.context parameters ('section group CTXSYS.JSON_SECTION_GROUP');
2.8.2.5 Using JSON Search Index with JSON_TEXTCONTAINS
The following example searches for customers having keyword "gold" in the description.
select customer_info from customers where JSON_TEXTCONTAINS(customer_info, '$.description', 'gold');
2.9 Classifier Types
The following classifier types are used to create preferences for CTS_CLS.TRAIN
and CTXRULE
index creation:
Note:
In Oracle Database Express Edition (Oracle Database XE), RULE_CLASSIFIER
, SVM_CLASSIFIER
, and SENTIMENT_CLASSIFIER
are not supported because the Data Mining option is not available. This is also true for KMEAN_CLUSTERING
.
2.9.1 RULE_CLASSIFIER
Use the RULE_CLASSIFIER
type for creating preferences for the query rule generating procedure, CTX_CLS.TRAIN
and for CTXRULE
creation. The rules generated with this type are essentially query strings and can be easily examined. The queries generated by this classifier can use the AND
, NOT
, or ABOUT
operators. The WITHIN
operator is supported for queries on field sections only.
Table 2-42 lists the attributes for the RULE_CLASSIFIER
type.
Table 2-42 RULE_CLASSIFIER Attributes
Attribute | Data Type | Default | Min Value | Max Value | Description |
---|---|---|---|---|---|
|
I |
50 |
1 |
99 |
Specify threshold (in percentage) for rule generation. One rule is output only when its confidence level is larger than threshold. |
|
I |
100 |
20 |
2000 |
For each class, a list of relevant terms is selected to form rules. Specify the maximum number of terms that can be selected for each class. |
|
I |
500 |
10 |
4000 |
Specify memory usage for training in MB. Larger values improve performance. |
|
F |
0.001 |
0 |
0.90 |
Specify a threshold for term selection. There are two thresholds guiding two steps in selecting relevant terms. This threshold controls the behavior of the first step. At this step, terms are selected as candidate terms for the further consideration in the second step. The term is chosen when the ratio of the occurrence frequency over the number of documents in the training set is larger than this threshold. |
|
I |
10 |
0 |
100 |
Specify a threshold as a percentage for term selection. This threshold controls the second step term selection. Each candidate term has a numerical quantity calculated to imply its correlation with a given class. The candidate term will be selected for this class only when the ratio of its quantity value over the maximum value for all candidate terms in the class is larger than this threshold. |
|
I |
75 |
0 |
100 |
Specify how much to prune a built decision tree for better coverage. Higher values mean more aggressive pruning and the generated rules will have larger coverage but less accuracy. |
2.9.2 SVM_CLASSIFIER
Use the SVM_CLASSIFIER
type for creating preferences for the rule generating procedure, CTX_CLS.TRAIN
, and for CTXRULE
creation. This classifier type represents the Support Vector Machine method of classification and generates rules in binary format. Use this classifier type when you need high classification accuracy.
This type has the following attributes:
Table 2-43 SVM_CLASSIFIER Attributes
Attribute Name | Data Type | Default | Min Value | Max Value | Description |
---|---|---|---|---|---|
|
I |
50 |
10 |
8192 |
Specify the maximum number of terms representing one document. |
|
I |
3,000 |
1 |
100,000 |
Specify the maximum number of distinct features. |
|
B |
FALSE |
NULL |
NULL |
Specify |
|
B |
TRUE |
NULL |
NULL |
Specify |
|
B |
FALSE |
NULL |
NULL |
Specify |
|
I |
500 |
10 |
4000 |
Specify approximate memory size in MB. |
|
1 |
2 |
0 |
100 |
Specify the occurrence multiplier for adding a term in a field section as a normal term. For example, by default, the term cat in "<A>cat</A>" is a field section term and is treated as a normal term with occurrence equal to 2, but you can specify that it be treated as a normal term with a weight up to 100. |
2.9.3 SENTIMENT_CLASSIFIER
Use the SENTIMENT_CLASSIFIER
type to create a preference for sentiment analysis queries. This classifier specifies preferences associated with a user-defined sentiment classifier preference. You must define a preference of this type before you use the CTX_CLS.SA_TRAIN_MODEL
procedure to train the user-defined sentiment classifier.
Table 2-44 lists the attributes for the SENTIMENT_CLASSIFIER
type.
Table 2-44 SENTIMENT_CLASSIFIER Attributes
Attribute | Data Type | Default | Minimum Value | Maximum Value | Description |
---|---|---|---|---|---|
MAX_DOCTERMS |
I | 50 | 10 | 8192 | Specify the maximum number of distinct terms representing one document |
MAX_FEATURES |
I | 3000 | 1 | 100000 | Specify the maximum number of distinct features used to build a sentiment classifier |
THEME_ON |
B | False | Specify if themes must be extracted as features | ||
TOKEN_ON |
B | True | Specify if tokens must be extracted as features | ||
STEM_ON |
B | True | Specify if stemmed tokens must be extracted as features | ||
MEMORY_SIZE |
I | 500 | 10 | 4000 | Specify the typical memory size, in MB, used to build the sentiment classifier. |
SECTION_WEIGHT |
I | 2 | 0 | 100 | Specify the integer multiplier for term occurrence within a field section |
NUM_ITERATIONS |
I | 600 | Specify the maximum number of iterations for which the sentiment classifier is run before it converges |
See Also:
Oracle Text Application
Developer's Guide for an example of using the SENTIMENT_CLASSIFIER
type
2.10 Cluster Types
This section describes the cluster types used for creating preferences for the CTX_CLS.CLUSTERING
procedure.
Note:
In Oracle Database Express Edition (Oracle Database XE), KMEAN_CLUSTERING
is not supported because the Data Mining option is not available. This is also true for RULE_CLASSIFIER
and SVM_CLASSIFIER
.
See Also:
For more information about clustering, see "CLUSTERING" in CTX_CLS Package as well as the Oracle Text Application Developer's Guide
2.10.1 KMEAN_CLUSTERING
The KMEAN_CLUSTERING
clustering type has the attributes listed in Table 2-45.
Table 2-45 KMEAN_CLUSTERING Attributes
Attribute Name | Data Type | Default | Min Value | Max Value | Description |
---|---|---|---|---|---|
|
I |
50 |
10 |
8192 |
Specify the maximum number of distinct terms representing one document. |
|
I |
3,000 |
1 |
500,000 |
Specify the maximum number of distinct features. |
|
B |
FALSE |
NULL |
NULL |
Specify |
|
B |
TRUE |
NULL |
NULL |
Specify |
|
B |
FALSE |
NULL |
NULL |
Specify |
|
I |
500 |
10 |
4000 |
Specify approximate memory size in MB. |
|
1 |
2 |
0 |
100 |
Specify the occurrence multiplier for adding a term in a field section as a normal term. For example, by default, the term cat in "<A>cat</A>" is a field section term and is treated as a normal term with occurrence equal to 2, but you can specify that it be treated as a normal term with a weight up to 100. |
|
I |
200 |
2 |
20000 |
Specify the total number of leaf clusters to be generated. |
2.11 Stoplists
Stoplists identify the words in your language that are not to be indexed. In English, you can also identify stopthemes that are not to be indexed. By default, the system indexes text using the system-supplied stoplist that corresponds to your database language.
Oracle Text provides default stoplists for most common languages including English, French, German, Spanish, Chinese, Dutch, and Danish. These default stoplists contain only stopwords.
See Also:
For more information about the supplied default stoplists, see Oracle Text Supplied Stoplists
2.11.1 Multi-Language Stoplists
You can create multi-language stoplists to hold language-specific stopwords. A multi-language stoplist is useful when you use the MULTI_LEXER
to index a table that contains documents in different languages, such as English, German.
To create a multi-language stoplist, use the CTX_DLL.
CREATE_STOPLIST procedure and specify a stoplist type of MULTI_STOPLIST
. Add language specific stopwords with CTX_DDL.
ADD_STOPWORD .
At indexing time, the language column of each document is examined, and only the stopwords for that language are eliminated. At query time, the session language setting determines the active stopwords, like it determines the active lexer when using the multi-lexer.
2.11.2 Creating Stoplists
Create your own stoplists using the CTX_DLL.
CREATE_STOPLIST procedure. With this procedure you can create a BASIC_STOPLIST
for single language stoplist, or you can create a MULTI_STOPLIST
for a multi-language stoplist.
When you create your own stoplist, you must specify it in the parameter clause of CREATE
INDEX
.
To create stoplists for Chinese or Japanese languages, use the CHINESE_LEXER
or JAPANESE_LEXER
respectively, and update the appropriate lexicon to be @contained_such_stopwords.
2.11.3 Modifying the Default Stoplist
The default stoplist is always named .CTXSYS.DEFAULT_STOPLIST
. Use the following procedures to modify this stoplist:
-
CTX_DDL.ADD_STOPWORD
-
CTX_DDL.REMOVE_STOPWORD
-
CTX_DDL.ADD_STOPTHEME
-
CTX_DDL.ADD_STOPCLASS
When you modify CTXSYS.DEFAULT_STOPLIST
with the CTX_DDL
package, you must re-create your index for the changes to take effect.
Dynamic Addition of Stopwords
You can add stopwords dynamically to a default or custom stoplist with ALTER INDEX . When you add a stopword dynamically, you need not re-index, because the word immediately becomes a stopword and is removed from the index.
Note:
Even though you can dynamically add stopwords to an index, you cannot dynamically remove stopwords. To remove a stopword, you must use CTX_DDL.REMOVE_STOPWORD , drop your index and re-create it.
See Also:
2.12 System-Defined Preferences
When you install Oracle Text, some indexing preferences are created. You can use these preferences in the parameter clause of CREATE INDEX or define your own.
The default index parameters are mapped to some of the system-defined preferences described in this section.
See Also:
For more information about default index parameters, see "Default Index Parameters"
System-defined preferences are divided into the following categories:
2.12.1 Data Storage Preferences
This section discusses the types associated with data storage preferences.
-
The
CTXSYS.DEFAULT_DATASTORE
preference uses the DIRECT_DATASTORE type. Use this preference to create indexes for text columns in which the text is stored directly in the column. -
The
CTXSYS.FILE_DATASTORE
preference uses the FILE_DATASTORE type. -
The
CTXSYS.URL_DATASTORE
preference uses the URL_DATASTORE type.
2.12.2 Filter Preferences
This section discusses the types associated with filtering preferences.
-
The
CTXSYS.NULL_FILTER
preference uses the NULL_FILTER type. -
The
CTXSYS.AUTO_FILTER
preference uses the AUTO_FILTER type.
2.12.3 Lexer Preferences
This section discusses the types associated with lexer preferences.
2.12.3.1 CTXSYS.DEFAULT_LEXER
The CTXSYS.DEFAULT_LEXER
default lexer depends on the language used at install time. The following sections describe the default settings for CTXSYS.DEFAULT_LEXER
for each language.
-
American and English Language Settings
If your language is English, this preference uses the BASIC_LEXER with the
index_themes
attribute disabled. -
If your language is Danish, this preference uses the BASIC_LEXER with the following option enabled:
-
Alternate spelling (alternate_spelling attribute set to
DANISH
)
-
-
If your language is Dutch, this preference uses the BASIC_LEXER with the following options enabled:
-
composite indexing (
composite
attribute set toDUTCH
)
-
-
German and German DIN Language Settings
If your language is German, then this preference uses the BASIC_LEXER with the following options enabled:
-
Case-sensitive indexing (
mixed_case
attribute enabled) -
Composite indexing (
composite
attribute set toGERMAN
) -
Alternate spelling (
alternate_spelling
attribute set toGERMAN
)
-
-
Finnish, Norwegian, and Swedish Language Settings
If your language is Finnish, Norwegian, or Swedish, this preference uses the BASIC_LEXER with the following option enabled:
-
Alternate spelling (alternate_spelling attribute set to
SWEDISH
)
-
-
If your language is Japanese, this preference uses the JAPANESE_VGRAM_LEXER.
-
If your language is Korean, this preference uses the KOREAN_MORPH_LEXER . All attributes for the
KOREAN_MORPH_LEXER
are enabled. -
If your language is Simplified or Traditional Chinese, this preference uses the CHINESE_VGRAM_LEXER.
-
Other Languages
For all other languages not listed in this section, this preference uses the BASIC_LEXER with no attributes set.
See Also:
To learn more about these options, see "BASIC_LEXER"
2.12.3.2 CTXSYS.DEFAULT_EXTRACT_LEXER
The CTXSYS.DEFAULT_EXTRACT_LEXER
preference uses AUTO_LEXER and includes all Oracle-supplied features (rules, dictionary, etc.). CTXSYS.DEFAULT_EXTRACT_LEXER
uses AUTO_LEXER with the following options:
-
alternate_spelling is NONE
-
base_letter is NO
-
mixed_case is YES
-
<> printjoin is '-*' <>
2.12.4 Section Group Preferences
This section discusses the types associated with section group preferences.
-
The
CTXSYS.NULL_SECTION_GROUP
preference uses theNULL_SECTION_GROUP
type. -
The
CTXSYS.HTML_SECTION_GROUP
preference uses theHTML_SECTION_GROUP
type. -
The
CTXSYS.JSON_SECTION_GROUP
preference uses thePATH_SECTION_GROUP
type. -
The
CTXSYS.AUTO_SECTION_GROUP
preference uses theAUTO_SECTION_GROUP
type. -
The
CTXSYS.PATH_SECTION_GROUP
preference uses thePATH_SECTION_GROUP
type.
Here is the list of default section groups that are created:
-
The
CTXSYS.XQUERY_SEC_GROUP
preference evaluates not only xquery full text expressions but also the xquery range expressions. -
The
CTXSYS.XQFT_SEC_GROUP
preference evaluates only xquery full text expressions.
2.12.5 Stoplist Preferences
This section discusses the types associated with stoplist preferences.
-
The
CTXSYS.DEFAULT_STOPLIST
stoplist preference defaults to the stoplist of your database language.
See Also:
For a complete list of the stop words in the supplied stoplists, see Oracle Text Supplied Stoplists
2.12.6 Storage Preferences
This section discusses the types associated with storage preferences.
The CTXSYS.DEFAULT_STORAGE
storage preference uses the BASIC_STORAGE type.
Here are the storage preferences:
-
The
CTXSYS.XQFT_LOW
preference disables the persistence of secondary XML representation into$D
table to save index storage space.-
xml_save_copy = FALSE
-
xml_forward_enable = FALSE
-
-
The
CTXSYS.XQFT_MEDIUM
preference enables the persistence of secondary XML representation into$D
table to reduce the time spent on post index xquery evaluation, if needed.-
xml_save_copy = TRUE
-
xml_forward_enable = FALSE
-
-
The
CTXSYS.XQFT_HIGH
preference enables the persistence of secondary XML representation into$D
table and forwards the index into$O
to reduce the time spent on post index xquery and xquery full text expression evaluation, if needed.-
xml_save_copy = TRUE
-
xml_forward_enable = TRUE
-
2.12.7 Wordlist Preferences
This section discusses the types associated with wordlist preferences.
The CTXSYS.DEFAULT_WORDLIST
preference uses the language stemmer for your database language. If your language is not listed in Table 2-38, then this preference defaults to the NULL
stemmer and the GENERIC
fuzzy matching attribute.
2.13 System Parameters
This section describes the Oracle Text system parameters, which are divided into the following categories:
See Also:
2.13.1 General System Parameters
When you install Oracle Text, in addition to the system-defined preferences, the following system parameters are set:
Table 2-46 General System Parameters
System Parameter | Description |
---|---|
|
This is the maximum indexing memory that can be specified in the parameter clause of |
|
This is the default indexing memory used with |
|
This is the directory for |
|
This is the default input key type, either See Also: CTX_DOC.SET_KEY_TYPE. |
View system defaults by querying the CTX_PARAMETERS view. Change defaults using the CTX_ADM.SET_PARAMETER procedure.
2.13.2 Default Index Parameters
This section describes the index parameters that you can use when you create CONTEXT
and CTXCAT
indexes.
This section contains the following topics:
Viewing Default Values
View system defaults by querying the CTX_PARAMETERS view. For example, to see all parameters and values, enter the following statement:
SQL> SELECT par_name, par_value from ctx_parameters;
Changing Default Values
Change a default value using the CTX_ADM.SET_PARAMETER procedure to name another custom or system-defined preference to use as default.
2.13.2.1 CONTEXT Index Parameters
The following default parameters are used when you create a CONTEXT
index and do not specify preferences in the parameter clause of CREATE INDEX. Each default parameter names a system-defined preference to use for data storage, filtering, lexing, and so on.
Table 2-47 Default CONTEXT Index Parameters
Parameter | Used When | Default Value |
---|---|---|
|
No datastore preference specified in parameter clause of |
|
|
No filter preference specified in parameter clause of
|
|
|
No filter preference specified in parameter clause of |
|
|
No filter preference specified in parameter clause of |
|
|
No section group specified in parameter clause of
|
|
|
No section group specified in parameter clause of |
|
|
No storage preference specified in parameter clause of |
|
|
No lexer preference specified in parameter clause of |
|
|
No stoplist specified in parameter clause of |
|
|
No wordlist preference specified in parameter clause of |
|
See Also:
2.13.2.2 CTXCAT Index Parameters
The following default parameters are used when you create a CTXCAT
index with CREATE
INDEX
and do not specify any parameters in the parameter string. The CTXCAT
index supports only the index set, lexer, storage, stoplist, and wordlist parameters. Each default parameter names a system-defined preference.
Table 2-48 Default CTXCAT Index Parameters
Parameter | Used When | Default Value |
---|---|---|
|
No index set specified in parameter clause of |
n/a |
|
No storage preference specified in parameter clause of |
|
|
No lexer preference specified in parameter clause of |
|
|
No stoplist specified in parameter clause of |
|
|
No wordlist preference specified in parameter clause of Note that while you can specify a wordlist preference for |
|
See Also:
2.13.2.3 CTXRULE Index Parameters
Table 2-49 lists the default parameters that are used when you create a CTXRULE
index with CREATE
INDEX
and do not specify any parameters in the parameter string. The CTXRULE
index supports only the lexer, storage, stoplist, and wordlist parameters. Each default parameter names a system-defined preference.
Table 2-49 Default CTXRULE Index Parameters
Parameter | Used When | Default Value |
---|---|---|
No lexer preference specified in parameter clause of |
|
|
No storage preference specified in parameter clause of |
|
|
No stoplist specified in parameter clause of |
|
|
No wordlist preference specified in parameter clause of |
|
|
No classifier preference is specified in parameter clause. |
|
See Also:
CTXRULE Index Limitations
The CTXRULE
index does not support the following query operators:
-
Fuzzy
-
Soundex
It also does not support the following BASIC_WORDLIST
attributes:
-
SUBSTRING_INDEX
-
PREFIX_INDEX
2.13.3 Default Policy Parameters
Policies in Oracle Text enable you to use document services without creating an index. For example, the document services might be filtering to generate a plain text or HTML version of a document, generating theme summaries or lists of themes, and highlighting.
Table 2-50 lists the default parameters when you create a policy and do not specify preferences when using CTX_DDL.CREATE_POLICY. Each default parameter names a system-defined preference to use for filtering, lexing, and so on.
Table 2-50 Default Policy Parameters for CTX_DDL.CREATE_POLICY
Parameter | Used When | Default Value |
---|---|---|
|
No filter preference specified for |
|
|
No filter preference specified for |
|
|
No section group specified for |
|
|
No |
|
|
No lexer preference specified for |
|
|
No stoplist specified for |
|
|
No wordlist preference specified for |
|
See Also:
-
"CREATE_POLICY" for complete information
2.14 Token Limitations for Oracle Text Indexes
Starting with Oracle Database Release 18c, the indexed token maximum size is increased to 255 characters for single-byte character sets.
Before Oracle Database Release 18c, all Oracle Text index types except SDATA
sections stored tokens in a table column of type VARCHAR2
(64 BYTE). Starting with Oracle Database Release 18c, all Oracle Text index types except CTXCAT
and CTXRULE
indexes store tokens in VARCHAR2
(255 BYTE) table column types. This change is an increase for the maximum size of an indexed token to 255 characters for single-byte character sets. The size increase is less with multibyte or variable-length character sets. Tokens longer than 255 bytes are truncated. Truncated tokens do not prevent searches on the whole token string. However, the system cannot distinguish between two tokens that have the same first 255 bytes.
Note:
Before Oracle Database Release 18c, tokens that were greater than 64 bytes were truncated to 64 bytes. After upgrading to Oracle Database Release 18c, the token tables are increased to 255 bytes from 64 bytes. Searches with more than 64 bytes in the search token (that is, any single word in search string) cannot find any tokens which were truncated to 64 bytes. To avoid this problem, rebuild the index. If you never use search tokens longer than 64 bytes, it is not necessary to rebuild the index.
SDATA
sections store tokens in a table column of type VARCHAR2
(249 BYTE). CTXCAT
and CTXRULE
indexes store tokens in a table column of type VARCHAR2
(64 BYTE).
2.15 Auditing Oracle Text DR$ Index Tables
You should consider creating audit policies for Oracle Text DR$
index tables, especially if the base index table has sensitive information.
2.15.1 About Auditing Oracle Text DR$ Index Tables
You can audit actions on Oracle Text index tables (DR$index
), which can contain sensitive data.
The audit can capture actions that a user will perform on the index table. You should create a unified audit policy for the table that contains the sensitive data, as well as the Oracle Text index table for the column containing the sensitive data. Oracle Text index table names start with a prefix of DR$
.
Index tables that do not contain customer data do not need audit policies. Tables that you should consider creating audit policies for include the following:
DR$index_name$I
(the main table that all users should protect)DR$index_name$G
(if present, stage_itab preference)DR$index_name$P
(if present, prefix index preference)DR$index_name$O
(if present, forward index preference)DR$index_name$D
(if present, save copy preference)DR$index_name$KG
(if present, wildcard index preference)DR$index_name$SN
,$ST
,$SD
,$SV
,$STZ
(if present,optimize_for_search
SDATA
preference )DR$index_name$S
(if present,optimize_for_sort
SDATA
preference)
You can find associated indexes with a particular table by querying the OBJECT_TYPE
column of the ALL_OBJECTS
data dictionary view. To find a list of internal Oracle Text tables, query the USER_TABLES
table, in the schema where index was created. For example, for an index named my_index
:
SELECT TABLE_NAME FROM USER_TABLES WHERE TABLE_NAME LIKE 'DR$my_index%';
2.15.2 Configuring an Oracle Text DR$ Index Tables Audit Policy
You can use the ACTIONS
clause in the CREATE AUDIT POLICY
statement to create a unified audit policy on Oracle Text DR$
index tables.
2.15.3 Example: Auditing Update Actions on an Oracle Text DR$ Index Table
The CREATE AUDIT POLICY
statement can audit all or specific actions on an Oracle Text DR$
index table.
Example 2-8 shows how to create and enable a unified audit policy for the emp_data
table that captures user update attempts on this table's Oracle Text index table, DR$emp_data_idx$I
.
Example 2-8 Auditing Update Actions on an Oracle Text DR$ Index Table
CREATE AUDIT POLICY emp_data_pol ACTIONS UPDATE ON emp_data, UPDATE ON DR$emp_data_idx$I; AUDIT POLICY emp_data_pol;
2.15.4 How Oracle Text DR$ Index Table Entries Appear in the Audit Trail
The UNIFIED_AUDIT_TRAIL
data dictionary view lists actions on audited Oracle Text DR$
index tables.
For example:
SELECT ACTION_NAME, OBJECT_SCHEMA, DBUSERNAME FROM UNIFIED_AUDIT_TRAIL WHERE OBJECT_NAME = 'DR$EMP_DATA_IDX$I'; ACTION_NAME OBJECT_SCHEMA DBUSERNAME ----------- ------------- ---------- UPDATE PRESTON FUSFERATU