1. Application Developer's Guide
  2. Searching Document Sections in Oracle Text

11 Searching Document Sections in Oracle Text

You can use document sections in a text query application.

This chapter contains the following topics:

11.1 About Oracle Text Document Section Searching

Section searching enables you to narrow text queries down to blocks of text within documents. Section searching is useful when your documents have internal structure, such as HTML and XML documents.

You can also search for text at the sentence and paragraph level.

This section contains these topics:

11.1.1 Enabling Oracle Text Section Searching

The steps for enabling section searching for your document collection are:

  1. Create a Section Group

  2. Define Your Sections

  3. Index Your Documents

  4. Section Searching with the WITHIN Operator

  5. Path Searching with INPATH and HASPATH Operators

  6. Marking an SDATA Section to be Searchable

11.1.1.1 Create a Section Group

You enable section searching by defining section groups. You use one of the system-defined section groups to create an instance of a section group. Choose a section group that is appropriate for your document collection.

You use section groups to specify the type of document set that you have and implicitly indicate the tag structure. For instance, to index HTML tagged documents, use HTML_SECTION_GROUP. Likewise, to index XML tagged documents, use XML_SECTION_GROUP.

Table 11-1 lists the different types of section groups.

Table 11-1 Types of Section Groups

Section Group Preference Description

NULL_SECTION_GROUP

This is the default. Use this group type when you define no sections or when you define only SENTENCE or PARAGRAPH sections.

BASIC_SECTION_GROUP

Use this group type for defining sections where the start and end tags are of the form <A> and </A>.

Note: This group type does not support input such as unbalanced parentheses, comments tags, and attributes. Use HTML_SECTION_GROUP for this type of input.

HTML_SECTION_GROUP

Use this group type to index HTML documents and for defining sections in HTML documents.

XML_SECTION_GROUP

Use this group type to index XML documents and for defining sections in XML documents.

AUTO_SECTION_GROUP

Use this group type to automatically create a zone section for each start-tag/end-tag pair in an XML document. As in XML, the section names derived from XML tags are case-sensitive.

Attribute sections are created automatically for XML tags that have attributes. Attribute sections are named in the form tag@attribute.

Stop sections, empty tags, processing instructions, and comments are not indexed.

The following limitations apply to automatic section groups:

  • You cannot add zone, field, or special sections to an automatic section group.

  • Automatic sectioning does not index XML document types (root elements.)

  • The length of the indexed tags, including prefix and namespace, cannot exceed 64 bytes. Tags longer than 64 bytes are not indexed.

PATH_SECTION_GROUP

Use this group type to index XML documents. This preference behaves like AUTO_SECTION_GROUP.

The difference is that you can search paths with the INPATH and HASPATH operators. Queries are also case-sensitive for tag and attribute names.

NEWS_SECTION_GROUP

Use this group to define sections in newsgroup-formatted documents according to RFC 1036.

Note:

Documents sent to the HTML, XML, AUTO, and PATH sectioners must begin with \s*<. The \s* represents zero or more whitespace characters. Otherwise, the document is treated as a plain-text document, and no sections are recognized.

You use the CTX_DDL package to create section groups and define sections as part of section groups. For example, to index HTML documents, create a section group with HTML_SECTION_GROUP: 

begin
ctx_ddl.create_section_group('htmgroup', 'HTML_SECTION_GROUP');
end;

Note:

Starting with Oracle Database 18c, use of NEWS_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.

11.1.1.2 Define Your Sections

You define sections as part of the section group. The following example defines a zone section called heading for all text within the HTML < H1> tag: 

begin
ctx_ddl.create_section_group('htmgroup', 'HTML_SECTION_GROUP');
ctx_ddl.add_zone_section('htmgroup', 'heading', 'H1');
end;

Note:

If you are using AUTO_SECTION_GROUP or PATH_SECTION_GROUP to index an XML document collection, then you do not have to explicitly define sections. The system defines the sections during indexing.

See Also:

11.1.1.3 Index Your Documents

When you index your documents, you specify your section group in the parameter clause of CREATE INDEX.

create index myindex on docs(htmlfile) indextype is ctxsys.context 
parameters('filter ctxsys.null_filter section group htmgroup');
11.1.1.4 Search Sections with the WITHIN Operator

When your documents are indexed, you can query within sections by using the WITHIN operator. For example, to find all documents that contain the word Oracle within their headings, enter the following query: 

'Oracle WITHIN heading'

See Also:

Oracle Text Reference to learn more about using the WITHIN operator

11.1.1.5 Search Paths with INPATH and HASPATH Operators

When you use PATH_SECTION_GROUP, the system automatically creates XML sections. In addition to using the WITHIN operator to enter queries, you can enter path queries with the INPATH and HASPATH operators.

See Also:

11.1.1.6 Mark an SDATA Section to Be Searchable
To mark an SDATA section to be searchable and have a $Sdatatype table created, use the CTX_DDL.SET_SECTION_ATTRIBUTE API.

The following tables are created:

  • $SN – NUMBER

  • $SD – DATE

  • $SV – VARCHAR2, CHAR

  • $SR – RAW

  • $SBD – BINARY DOUBLE

  • $SBF – BINARY FLOAT

  • $ST – TIMESTAMP

  • $STZ – TIMESTAMP WITH TIMEZONE

The following example creates a $SV table for this SDATA section to allow efficient searching on that section.
ctx_ddl.add_sdata_section('sec_grp', 'sdata_sec', 'mytag', 'varchar');
ctx_ddl.set_section_attribute('sec_grp', 'sdata_sec', 'optimized_for', 'search');

The default value of this attribute is FALSE.

11.1.2 Oracle Text Section Types

All section types are blocks of text in a document. However, sections can differ in the way that they are delimited and the way that they are recorded in the index. Sections can be one of the following types:

Table 11-2 shows which section types may be used with each kind of section group.

Table 11-2 Section Types and Section Groups

Section Group ZONE FIELD STOP MDATA NDATA SDATA ATTRIBUTE SPECIAL

NULL

NO

NO

NO

NO

NO

NO

NO

YES

BASIC

YES

YES

NO

YES

YES

YES

NO

YES

HTML

YES

YES

NO

YES

YES

YES

NO

YES

XML

YES

YES

NO

YES

YES

YES

YES

YES

NEWS

YES

YES

NO

YES

YES

YES

NO

YES

AUTO

NO

NO

YES

NO

NO

NO

NO

NO

PATH

NO

NO

NO

NO

NO

NO

NO

NO
11.1.2.1 Zone Section

A zone section is a body of text delimited by start and end tags in a document. The positions of the start and end tags are recorded in the index so that any words in between the tags are considered to be within the section. Any instance of a zone section must have a start and an end tag.

For example, define the text between the <TITLE> and </TITLE> tags as a zone section as follows: 

<TITLE>Tale of Two Cities</TITLE>
It was the best of times...

Zone sections can nest, overlap, and repeat within a document.

When querying zone sections, you use the WITHIN operator to search for a term across all sections. Oracle Text returns those documents that contain the term within the defined section.

Zone sections are well suited for defining sections in HTML and XML documents. To define a zone section, use CTX_DDL.ADD_ZONE_SECTION.

For example, assume you define the booktitle section as follows: 

begin
ctx_ddl.create_section_group('htmgroup', 'HTML_SECTION_GROUP');
ctx_ddl.add_zone_section('htmgroup', 'booktitle', 'TITLE');
end;

After you index, you can search for all documents that contain the term Cities within the booktitle section as follows: 

'Cities WITHIN booktitle'

With multiple query terms such as (dog and cat) WITHIN booktitle, Oracle Text returns those documents that contain cat and dog within the same instance of a booktitle section.

Repeated Zone Sections

Zone sections can repeat. Each occurrence is treated as a separate section. For example, if <H1> denotes a heading section, the heading can be repeated in the same documents as follows: 

<H1> The Brown Fox </H1>
<H1> The Gray Wolf </H1>

Assuming that these zone sections are named Heading, a query of Brown WITHIN Heading returns this document. However, a query of (Brown and Gray) WITHIN Heading does not.

Overlapping Zone Sections

Zone sections can overlap each other. For example, if <B> and <I> denote two different zone sections, they can overlap in a document as follows: 

plain <B> bold <I> bold and italic </B> only italic </I>  plain

Nested Zone Sections

Zone sections can be nested, as follows:

<TD> <TABLE><TD>nested cell</TD></TABLE></TD>

Using the WITHIN operator, you can write queries to search for text in sections within sections. For example, assume that the BOOK1, BOOK2, and AUTHOR zone sections occur as follows in the doc1 and doc2 documents:

doc1:

<book1> <author>Scott Tiger</author> This is a cool book to read.</book1>

doc2:

<book2> <author>Scott Tiger</author> This is a great book to read.</book2>

Consider the nested query. It returns only doc1.

'(Scott within author) within book1'
11.1.2.2 Field Section

A field section is similar to a zone section in that it is a region of text delimited by start and end tags. Field sections are more efficient from zone sections and are different than zone sections in that the region is indexed separately from the rest of the document. You can create an unlimited number of field sections.

Because field sections are indexed differently, you can also get better query performance over zone sections when a large number of documents are indexed.

Field sections are more suited to a single occurrence of a section in a document, such as a field in a news header. Field sections can also be made visible to the rest of the document.

Unlike zone sections, field sections have the following restrictions:

  • They cannot overlap.

  • They cannot repeat.

  • They cannot nest.

Visible and Invisible Field Sections

By default, field sections are indexed as a sub-document separate from the rest of the document. As such, field sections are invisible to the surrounding text and can only be queried by explicitly naming the section in the WITHIN clause.

You can make field sections visible if you want the text within the field section to be indexed as part of the enclosing document. You can query text within a visible field section with or without the WITHIN operator.

The following example shows the difference using invisible and visible field sections. The code defines a basicgroup section group of the BASIC_SECTION_GROUP type. It then creates a field section in basicgroup called Author for the <A> tag. It also sets the visible flag to FALSE to create an invisible section. 

begin
ctx_ddl.create_section_group('basicgroup', 'BASIC_SECTION_GROUP');
ctx_ddl.add_field_section('basicgroup', 'Author', 'A', FALSE);
end;

Because the Author field section is not visible, to find text within the Author section, you must use the WITHIN operator. 

'(Martin Luther King) WITHIN Author'

A query of Martin Luther King without the WITHIN operator does not return instances of this term in field sections. If you want to query text within field sections without specifying WITHIN, you must set the visible flag to TRUE when you create the section, as follows: 

begin
ctx_ddl.add_field_section('basicgroup', 'Author', 'A', TRUE);
end;

Nested Field Sections

You cannot nest field sections. For example, if you define a field section to start with <TITLE> and define another field section to start with <FOO>, you cannot nest the two sections as follows: 

<TITLE> dog <FOO> cat </FOO> </TITLE>

To work with nested sections, define them as zone sections.

Repeated Field Sections

Repeated field sections are allowed, but WITHIN queries treat them as a single section. Here is an example of a repeated field section in a document: 

<TITLE> cat </TITLE>
<TITLE> dog </TITLE>

The query dog and cat within title returns the document, even though these words occur in different sections.

To have WITHIN queries distinguish repeated sections, define them as zone sections.

11.1.2.3 Stop Section

When you add a stop section to an automatic section group, the automatic section indexing operation ignores the specified section in XML documents.

Note:

Adding a stop section causes no section information to be created in the index. However, the text within a stop section is always searchable.

Adding a stop section is useful when your documents contain many low-information tags. Adding stop sections also improves indexing performance with the automatic section group.

You can add an unlimited number of stop sections.

Stop sections do not have section names and are not recorded in the section views.

11.1.2.4 MDATA Section

You use an MDATA section to reference user-defined metadata for a document. MDATA sections can speed up mixed queries, and there is no limit to the number of MDATA sections that can be returned in a query.

Consider the case where you want to query according to text content and document type (magazine, newspaper, or novel). You can create an index with a column for text and a column for the document type, and then perform a mixed query of this form. In this case, search for all novels with the phrase Adam Thorpe (author of the novel Ulverton): 

SELECT id FROM documents
   WHERE doctype = 'novel'
      AND CONTAINS(text, 'Adam Thorpe')>0;

However, it is usually faster to incorporate the attribute (in this case, the document type) in a field section, rather than using a separate column, and then using a single CONTAINS query. 

SELECT id FROM documents
  WHERE CONTAINS(text, 'Adam Thorpe AND novel WITHIN doctype')>0;

This approach has two drawbacks:

  • Each time the attribute is updated, the entire text document must be reindexed, resulting in increased index fragmentation and slower rates of data manipulation language (DML) processing.

  • Field sections tokenize the section value. Tokenization has several effects. Special characters in metadata, such as decimal points or currency characters, are not easily searchable; value searching (searching for John Smith but not John Smith, Jr.) is difficult; multiword values are queried by phrase, which is slower than single-token searching; and multiword values do not show up in browsed words, making author browsing or subject browsing impossible.

For these reasons, using MDATA sections instead of field sections may be worthwhile. MDATA sections are indexed like field sections, but you can add and remove metadata values from documents without the need to reindex the document text. Unlike field sections, MDATA values are not tokenized. Additionally, MDATA section indexing generally takes up less disk space than field section indexing.

Starting with Oracle Database 12c Release 2 (12.2), the MDATA section can be updatable or nonupdatable depending on the value of its read-only tag, which can be set to either FALSE or TRUE.

Use CTX_DDL.ADD_MDATA_SECTION to add an MDATA section to a section group. By default, the value of a read-only MDATA section is FALSE. It implies that you want to permit calling CTX_DDL.ADD_MDATA() and CTX_DDL.REMOVE_MDATA() for this MDATA section, otherwise you can set it to TRUE. When set to FALSE, the queries on the MDATA section run less efficiently because a cursor must be opened on the index table to track the deleted values for that MDATA section. This example adds an MDATA section called AUTHOR and gives it the value Soseki Natsume (author of the novel Kokoro). 

ctx_ddl.create.section.group('htmgroup', 'HTML_SECTION_GROUP');
ctx_ddl.add_mdata_section('htmgroup', 'author', 'Soseki Natsume');

You can change MDATA values with CTX_DDL.ADD_MDATA, and you can remove them with CTX_DDL.REMOVE_MDATA. Also, MDATA sections can have multiple values. Only the owner of the index may call CTX_DDL.ADD_MDATA and CTX_DDL.REMOVE_MDATA.

Neither CTX_DDL.ADD_MDATA nor CTX_DDL.REMOVE_MDATA is supported for CTXCAT and CTXRULE indexes.

MDATA values are not passed through a lexer. Instead, all values undergo the following simplified normalization:

  • Leading and trailing whitespace on the value is removed.

  • The value is truncated to 255 bytes.

  • The value is indexed as a single value; if the value consists of multiple words, it is not broken up.

  • Case is preserved. If the document is dynamically generated, you can implement case-insensitivity by uppercasing MDATA values and making sure to search only in uppercase.

After you add MDATA metadata to a document, you can query for that metadata by using the CONTAINS query operator: 

SELECT id FROM documents
   WHERE CONTAINS(text, 'Tokyo and MDATA(author, Soseki Natsume)')>0;

This query is only successful if an AUTHOR tag has the exact value Soseki Natsume (after simplified tokenization). Soseki or Natsume Soseki returns no rows.

The following are considerations for MDATA:

  • MDATA values are not highlightable, do not appear in the output of CTX_DOC.TOKENS, and do not appear when you enable FILTER PLAINTEXT.

  • MDATA sections must be unique within section groups. For example, do not use FOO as the name of an MDATA section and a zone or field section in the same section group.

  • Like field sections, MDATA sections cannot overlap or nest. An MDATA section is implicitly closed by the first tag encountered. In this example: 

    <AUTHOR>Dickens <B>Shelley</B> Keats</AUTHOR>

    The <B> tag closes the AUTHOR MDATA section; as a result, this document has an AUTHOR of 'Dickens', but not of 'Shelley' or 'Keats'.

  • To prevent race conditions, each call to ADD_MDATA and REMOVE_MDATA locks out other calls on that rowid for that index for all values and sections. However, because ADD_MDATA and REMOVE_MDATA do not commit, it is possible for an application to deadlock when calling them both. It is the application's responsibility to prevent deadlocking.

See Also:

11.1.2.5 NDATA Section

For fields containing data to be indexed for name searching, you can specify them exclusively by adding NDATA sections to section groups of type BASIC_SECTION_GROUP, HTML_SECTION_GROUP, or XML_SECTION_GROUP.

Users can synthesize textual documents, which contain name data, by using two possible datastores: MULTI_COLUMN_DATASTORE or USER_DATASTORE. The following example uses MULTI_COLUMN_DATASTORE to pick up relevant columns containing the name data for indexing: 

create table people(firstname varchar2(80), surname varchar2(80));
 insert into people values('John', 'Smith');
 commit;
 begin
   ctx_ddl.create_preference('nameds', 'MULTI_COLUMN_DATASTORE');
   ctx_ddl.set_attribute('nameds', 'columns', 'firstname,surname');
 end;
 /

This example produces the following virtual text for indexing:

<FIRSTNAME>
John
</FIRSTNAME>
<SURNAME>
Smith
</SURNAME>

You can then create NDATA sections for FIRSTNAME and SURNAME sections: 

begin
  ctx_ddl.create_section_group('namegroup', 'BASIC_SECTION_GROUP');
  ctx_ddl.add_ndata_section('namegroup', 'FIRSTNAME', 'FIRSTNAME');
  ctx_ddl.add_ndata_section('namegroup', 'SURNAME', 'SURNAME');
end;
/

Next, create the index by using the datastore preference and section group preference that you created earlier:

create index peopleidx on people(firstname) indextype is ctxsys.context
parameters('section group namegroup datastore nameds');

NDATA sections support both single- and multibyte data with character- and term-based limitations. NDATA section data that is indexed is constrained as follows:

  • The number of characters in a single, whitespace-delimited term: 511

  • The number of whitespace-delimited terms: 255

  • The total number of characters, including whitespaces: 511

11.1.2.6 SDATA Section

The value of an SDATA section is extracted from the document text like other sections, but it is indexed as structured data, also referred to as SDATA. SDATA sections support operations such as projection, range searches, and ordering. SDATA sections also enable SDATA indexing of section data (such as embedded tags) and detail table or function invocations. You can perform various combinations of text and structured searches in one single SQL statement.

Use SDATA operators only as descendants of AND operators that also have non-SDATA children. SDATA operators are meant to be used as secondary (checking or non-driving) criteria. For example, "find documents with DOG that also have price > 5", rather than "find documents with rating > 4".

Use CTX_DDL.ADD_SDATA_SECTION to add an SDATA section to a section group. Use CTX_DDL.UPDATE_SDATA to update the values of an existing SDATA section. When querying within an SDATA section, you must use the CONTAINS operator. The following example creates a table called items, adds an SDATA section called my_sec_group, and then queries SDATA in the section.

After you create an SDATA section, you can further modify the attributes of the SDATA section by using CTX_DDL.SET_SECTION_ATTRIBUTE.

Create the items table: 

CREATE TABLE items 
(id  NUMBER PRIMARY KEY, 
 doc VARCHAR2(4000));
 
INSERT INTO items VALUES (1, '<description> Honda Pilot </description>
                              <category> Cars & Trucks </category>
                              <price> 27000 </price>');
INSERT INTO items VALUES (2, '<description> Toyota Sequoia </description>
                              <category> Cars & Trucks </category>
                              <price> 35000 </price>');
INSERT INTO items VALUES (3, '<description> Toyota Land Cruiser </description>
                              <category> Cars & Trucks </category>
                              <price> 45000 </price>');
INSERT INTO items VALUES (4, '<description> Palm Pilot </description>
                              <category> Electronics </category>
                              <price> 5 </price>');
INSERT INTO items VALUES (5, '<description> Toyota Land Cruiser Grill </description>
                              <category> Parts & Accessories </category>
                              <price> 100 </price>');
COMMIT;

Add the my_sec_group SDATA section: 

BEGIN
  CTX_DDL.CREATE_SECTION_GROUP('my_sec_group', 'BASIC_SECTION_GROUP');
  CTX_DDL.ADD_SDATA_SECTION('my_sec_group', 'category', 'category', 'VARCHAR2');
  CTX_DDL.ADD_SDATA_SECTION('my_sec_group', 'price', 'price', 'NUMBER');
END;

Create the CONTEXT index: 

CREATE INDEX items$doc 
  ON items(doc) 
  INDEXTYPE IS CTXSYS.CONTEXT
  PARAMETERS('SECTION GROUP my_sec_group');

Run a query:

SELECT id, doc
  FROM items
  WHERE contains(doc, 'Toyota 
                       AND SDATA(category = ''Cars & Trucks'') 
                       AND SDATA(price <= 40000 )') > 0;

Return the results:

  ID DOC
---- ----------------------------------------------------------------------
   2 <description> Toyota Sequoia </description>
                                   <category> Cars & Trucks </category>
                                   <price> 35000 </price>

Consider a document whose rowid is 1. This example updates the value of the price SDATA section to a new value of 30000: 

BEGIN
    SELECT ROWID INTO rowid_to_update FROM items WHERE id=1;

    CTX_DDL.UPDATE_SDATA('items$doc', 
                         'price',
                         SYS.ANYDATA.CONVERTVARCHAR2('30000'),
                         rowid_to_update);
END;

After executing the query, the price of Honda Pilot is changed from 27000 to 30000.

Note:

  • You can also add an SDATA section to an existing index. Use the ADD SDATA SECTION parameter of the ALTER INDEX PARAMETERS statement. See the "ALTER INDEX" section of the Oracle Text Reference for more information.

  • Documents that were indexed before adding an SDATA section do not reflect this new preference. Rebuild the index in this case.

See Also:

  • The "CONTAINS" query section of the Oracle Text Reference for information on the SDATA operator

  • The "CTX_DDL" package section of the Oracle Text Reference for information on adding and updating the SDATA sections and changing their attributes by using the ADD_SDATA_SECTION, SET_SECTION_ATTRIBUTE, and the UPDATE_SDATA procedures

Storage

For optimized_for search SDATA sections, use CTX_DDL.SET_ATTRIBUTE to specify the storage preferences for the $Sdatatype tables and the indexes on these tables.

By default, large object (LOB) caching is turned on for $S* tables and off for $S* indexes. These attributes are valid only on SDATA sections.

Query Operators

optimized_for search SDATA supports the following query operators:

  • =

  • <>

  • between

  • not between

  • <=

  • <

  • >=

  • >

  • is null

  • is not null

  • like

  • not like

11.1.2.7 Attribute Section

You can define attribute sections to query on XML attribute text. You can also have the system automatically define and index XML attributes for you.

See Also:

"XML Section Searching with Oracle Text"

11.1.2.8 Special Sections

Special sections are not recognized by tags. Currently, sentence and paragraph are the only supported special sections, and they enable you to search for a combination of words within sentences or paragraphs.

The sentence and paragraph boundaries are determined by the lexer. For example, BASIC_LEXER recognizes sentence and paragraph section boundaries as follows:

Table 11-3 Sentence and Paragraph Section Boundaries for BASIC_LEXER

Special Section Boundary

SENTENCE

  • WORD/PUNCT/WHITESPACE

  • WORD/PUNCT/NEWLINE

PARAGRAPH

  • WORD/PUNCT/NEWLINE/WHITESPACE

  • WORD/PUNCT/NEWLINE/NEWLINE

If the lexer cannot recognize the boundaries, then no sentence or paragraph sections are indexed.

To add a special section, use the CTX_DDL.ADD_SPECIAL_SECTION procedure. For example, the following code enables searches within sentences in HTML documents: 

begin
ctx_ddl.create_section_group('htmgroup', 'HTML_SECTION_GROUP');
ctx_ddl.add_special_section('htmgroup', 'SENTENCE');
end;

To enable zone and sentence searches, add zone sections to the group. The following example adds the Headline zone section to the htmgroup section group: 

begin
ctx_ddl.create_section_group('htmgroup', 'HTML_SECTION_GROUP');
ctx_ddl.add_special_section('htmgroup', 'SENTENCE');
ctx_ddl.add_zone_section('htmgroup', 'Headline', 'H1');
end;

11.1.3 Oracle Text Section Attributes

Section attributes are the attributes that can be specified at the section level rather than at the index level. Currently, the visible section attribute is supported for sections of field type.

You can set the visible section attribute for field sections using the CTX_DDL.ADD_FIELD_SECTION API directly. You can set this attribute to one of the following values:

  • FALSE: This is the default value. The text in the field section is indexed separately from the rest of the document.

  • TRUE: You can set this value if you want to make the text visible within a document. The text in the field section is indexed as part of the enclosing document.

The syntax is as follows:

CTX_DDL.ADD_FIELD_SECTION(
  group_name     IN    VARCHAR2,
  section_name   IN    VARCHAR2,
  tag            IN    VARCHAR2,
  visible        IN    BOOLEAN default FALSE
);

The following example enables the visible attribute for a field section: 

begin
ctx_ddl.create_section_group(‘fieldgroup', ‘BASIC_SECTION_GROUP');
ctx_ddl.add_field_section(‘fieldgroup', ‘author', ‘AUTHOR', TRUE);
end;

You can use the ALTER INDEX REBUILD syntax to alter the visible attribute as follows: 

ADD FIELD SECTION section_name tag tag [(VISIBLE | INVISIBLE)]

Related Topics

11.2 HTML Section Searching with Oracle Text

HTML has internal structure in the form of tagged text that you can use for section searching. For example, define a section called headings for the <H1> tag, and then search for terms only within these tags across your document set.

To query, you use the WITHIN operator. Oracle Text returns all documents that contain your query term within the headings section. For example, if you want to find all documents that contain the word oracle within headings, enter the following query: 

'oracle within headings'

This section contains these topics:

11.2.1 Creating HTML Sections

The following code defines a section group called htmgroup of type HTML_SECTION_GROUP. It then creates a zone section in htmgroup called heading identified by the <H1> tag: 

begin
ctx_ddl.create_section_group('htmgroup', 'HTML_SECTION_GROUP');
ctx_ddl.add_zone_section('htmgroup', 'heading', 'H1');
end;

You can then index your documents as follows:

create index myindex on docs(htmlfile) indextype is ctxsys.context
parameters('filter ctxsys.null_filter section group htmgroup');

After indexing with the htmgroup section group, you can query within the heading section by issuing this query: 

'Oracle WITHIN heading'

11.2.2 Searching HTML Meta Tags

With HTML documents, you can also create sections for NAME/CONTENT pairs in <META> tags. When you do so, you can limit your searches to text within CONTENT.

Consider an HTML document that has the following META tag: 

<META NAME="author" CONTENT="ken">

Create a zone section that indexes all CONTENT attributes for the META tag whose NAME value is author: 

begin
ctx_ddl.create_section_group('htmgroup', 'HTML_SECTION_GROUP');
ctx_ddl.add_zone_section('htmgroup', 'author', 'meta@author');
end

After indexing with the htmgroup section group, you can query the document: 

'ken WITHIN author'

11.3 XML Section Searching with Oracle Text

Like HTML documents, XML documents have tagged text that you can use to define blocks of text for section searching. You can search the contents of a section with the WITHIN or INPATH operators.

The following sections describe the different types of XML searching:

11.3.1 Automatic Sectioning

To set up your indexing operation to automatically create sections from XML documents, use the AUTO_SECTION_GROUP section group. The system creates zone sections for XML tags. Attribute sections are created for the tags that have attributes and for the sections named in the form tag@attribute.

For example, the following statement uses the AUTO_SECTION_GROUP to create the myindex index on a column containing the XML files: 

CREATE INDEX myindex
ON xmldocs(xmlfile)
 INDEXTYPE IS ctxsys.context
PARAMETERS ('datastore ctxsys.default_datastore 
             filter ctxsys.null_filter 
             section group ctxsys.auto_section_group'
           );

11.3.2 Attribute Searching

You can search XML attribute text in one of two ways:

  • Creating Attribute Sections

    Create attribute sections with CTX_DDL.ADD_ATTR_SECTION and then index with XML_SECTION_GROUP. If you use AUTO_SECTION_GROUP when you index, attribute sections are created automatically. You can query attribute sections with the WITHIN operator.

    Consider an XML file that defines the BOOK tag with a TITLE attribute: 

    <BOOK TITLE="Tale of Two Cities"> 
  It was the best of times. 
</BOOK>

    To define the title attribute as an attribute section, create an XML_SECTION_GROUP and define the attribute section: 

    begin
ctx_ddl.create_section_group('myxmlgroup', 'XML_SECTION_GROUP');
ctx_ddl.add_attr_section('myxmlgroup', 'booktitle', 'book@title');
end;

    To index:

    CREATE INDEX myindex
ON xmldocs(xmlfile)
INDEXTYPE IS ctxsys.context
PARAMETERS ('datastore ctxsys.default_datastore 
             filter ctxsys.null_filter 
             section group myxmlgroup'
           );

    To query the booktitle XML attribute section: 

    'Cities within booktitle'

  • Searching Attributes with the INPATH Operator

    Index with the PATH_SECTION_GROUP and query attribute text with the INPATH operator.

See Also:

"Path Section Searching"

11.3.3 Document Type Sensitive Sections

For an XML document set that contains the <book> tag declared for different document types, you may want to create a distinct book section for each document type to improve search capability. The following scenario shows you how to create book sections for each document type.

Assume that mydocname1 is declared as an XML document type (root element): 

<!DOCTYPE mydocname1 ... [...

Within mydocname1,, the <book> element is declared. For this tag, you can create a section named mybooksec1 that is sensitive to the tag's document type: 

begin
ctx_ddl.create_section_group('myxmlgroup', 'XML_SECTION_GROUP');
ctx_ddl.add_zone_section('myxmlgroup', 'mybooksec1', 'mydocname1(book)');
end;

Assume that mydocname2 is declared as another XML document type (root element): 

<!DOCTYPE mydocname2 ... [...

Within mydocname2,, the <book> element is declared. For this tag, you can create a section named mybooksec2 that is sensitive to the tag's document type: 

begin
ctx_ddl.create_section_group('myxmlgroup', 'XML_SECTION_GROUP');
ctx_ddl.add_zone_section('myxmlgroup', 'mybooksec2', 'mydocname2(book)');
end;

To query within the mybooksec1 section, use WITHIN: 

'oracle within mybooksec1'

11.3.4 Path Section Searching

XML documents can have parent-child tag structures such as:

<A> <B> <C> dog </C> </B> </A>

In this scenario, tag C is a child of tag B, which is a child of tag A.

With Oracle Text, you can search paths with PATH_SECTION_GROUP. This section group enables you to specify direct parentage in queries, such as to find all documents that contain the term dog in element C, which is a child of element B, and so on.

With PATH_SECTION_GROUP, you can also perform attribute value searching and attribute equality testing.

The new operators associated with this feature are

  • INPATH

  • HASPATH

This section contains the following topics.

11.3.4.1 Creating an Index with PATH_SECTION_GROUP

To enable path section searching, index your XML document set with PATH_SECTION_GROUP. For example:

Create the preference.

begin
ctx_ddl.create_section_group('xmlpathgroup', 'PATH_SECTION_GROUP');
end;

Create the index.

CREATE INDEX myindex
ON xmldocs(xmlfile)
INDEXTYPE IS ctxsys.context
PARAMETERS ('datastore ctxsys.default_datastore 
             filter ctxsys.null_filter 
             section group xmlpathgroup'
           );
When you create the index, you can use the INPATH and HASPATH operators.
                        

                     

                  
11.3.4.2 Top-Level Tag Searching
                     

                     

                        
To find all documents that contain the term dog in the top-level tag <A>:
dog INPATH (/A)

or
dog INPATH(A)

                  
11.3.4.3 Any-Level Tag Searching
                     

                     

                        
To find all documents that contain the term dog in the <A> tag at any level:
                        
dog INPATH(//A)

This query finds the following documents:
<A>dog</A>

and
<C><B><A>dog</A></B></C>

                  
11.3.4.4 Direct Parentage Searching
                     

                     

                        
To find all documents that contain the term dog in a B element that is a direct child of a top-level A element:
                        
dog INPATH(A/B)

This query finds the following XML document:
<A><B>My dog is friendly.</B></A>

but it does not find:
<C><B>My dog is friendly.</B></C>

                  
11.3.4.5 Tag Value Testing
                     

                     

                        
You can test the value of tags. For example, the query:
dog INPATH(A[B="dog"])

Finds the following document:
<A><B>dog</B></A>

But does not find:
<A><B>My dog is friendly.</B></A>

                  
11.3.4.6 Attribute Searching
                     

                     

                        
You can search the content of attributes. For example, the query:
dog INPATH(//A/@B)

Finds the document:
<C><A  B="snoop dog"> </A> </C>

                  
11.3.4.7 Attribute Value Testing
                     

                     

                        
You can test the value of attributes. For example, the query:
California INPATH (//A[@B = "home address"])

Finds the document:
<A B="home address">San Francisco, California, USA</A>

But it does not find:
<A B="work address">San Francisco, California, USA</A>

                  
11.3.4.8 Path Testing
                     

                     

                        
You can test if a path exists with the HASPATH operator. For example, the query:
                        
HASPATH(A/B/C)

finds and returns a score of 100 for the document
<A><B><C>dog</C></B></A>

without the query having to reference dog at all.
                        

                     

                  
11.3.4.9 Section Equality Testing with HASPATH 
                     

                     

                        
You can use the HASPATH operator for section quality tests. For example, consider the following query:
                        
dog INPATH A

It finds:
<A>dog</A>

but it also finds:
<A>dog park</A>

To limit the query to the term dog and nothing else, you can use a section equality test with the HASPATH operator. For example,
                        
HASPATH(A="dog")

finds and returns a score of 100 only for the first document, not for the second document.

                        

                           
See Also:

                           
Oracle Text Reference to learn more about using the INPATH and HASPATH operators