|Oracle® Text Reference
11g Release 2 (11.2)
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This chapter discusses the utilities shipped with Oracle Text. The following topics are included:
An import file is an ASCII flat file that contains entries for synonyms, broader terms, narrower terms, or related terms, which can be used to expand queries.
See Also:For examples of import files for thesaurus importing, see "Structure of ctxload Thesaurus Import File" in Appendix C, "Text Loading Examples for Oracle Text"
ctxload program no longer supports the loading of text columns. To load files to a text column in batch mode, Oracle recommends that you use SQL*Loader.
ctxload -user username[/password][@sqlnet_address] -name object_name -file file_name [-thes] [-thescase y|n] [-thesdump] [-log file_name] [-trace] [-drop]
Specify the user name and password of the user running
The user name and password can be followed immediately by @sqlnet_address to permit logging on to remote databases. The value for sqlnet_address is a database connect string. If the
TWO_TASK environment variable is set to a remote database, then you do not need to specify a value for sqlnet_address to connect to the database.
When you use
ctxload to import a thesaurus, use
object_name to specify the name of the thesaurus to be imported.
object_name to identify the thesaurus in queries that use thesaurus operators.
Note:Thesaurus name must be unique. If the name specified for the thesaurus is identical to an existing thesaurus, then
ctxloadreturns an error and does not overwrite the existing thesaurus.
ctxload is used to import a thesaurus, use file_name to specify the name of the import file that contains the thesaurus entries.
ctxload is used to export a thesaurus, use file_name to specify the name of the export file created by
Note:If the name specified for the thesaurus dump file is identical to an existing file, then
ctxloadoverwrites the existing file.
Import a thesaurus. Specify the source file with the -file argument. Specify the name of the thesaurus to be imported with -name.
Specify y to create a case-sensitive thesaurus with the name specified by -name and populate the thesaurus with entries from the thesaurus import file specified by -file. If -thescase is y (the thesaurus is case-sensitive),
ctxload enters the terms in the thesaurus exactly as they appear in the import file.
The default for -thescase is n (case-insensitive thesaurus).
Note:-thescase is valid for use only with the -thes argument.
Export a thesaurus. Specify the name of the thesaurus to be exported with the -name argument. Specify the destination file with the -file argument.
Specify the name of the log file to which
ctxload writes any national-language supported (Globalization Support) messages generated during processing. If you do not specify a log file name, the messages appear on the standard output.
Enables SQL statement tracing using
TRUE. This command captures all processed SQL statements in a trace file, which can be used for debugging. The location of the trace file is operating-system dependent and can be modified using the
USER_DUMP_DEST initialization parameter.
See Also:For more information about SQL trace and the
USER_DUMP_DESTinitialization parameter, see Oracle Database Administrator's Guide
This section provides examples for some of the operations that
ctxload can perform.
See Also:For more document loading examples, see Appendix C, "Text Loading Examples for Oracle Text"
The following example imports a thesaurus named
tech_doc from an import file named
ctxload -user jsmith/123abc -thes -name tech_doc -file tech_thesaurus.txt
The following example dumps the contents of a thesaurus named
tech_doc into a file named
ctxload -user jsmith/123abc -thesdump -name tech_doc -file tech_thesaurus.out
The knowledge base is the information source that Oracle Text uses to perform theme analysis, such as theme indexing, processing
ABOUT queries, and to document theme extraction with the
CTX_DOC package. A knowledge base is supplied for English and French.
ctxkbtc compiler, you can:
Extend your knowledge base by compiling one or more thesauri with the Oracle Text knowledge base. The extended information can be application-specific terms and relationships. During theme analysis, the extended portion of the knowledge base overrides any terms and relationships in the knowledge base where there is overlap.
Create a new user-defined knowledge base by compiling one or more thesauri. In languages other than English and French, this feature can be used to create a language-specific knowledge base.
CTXSYScan extend the knowledge base.
See Also:For more information about the knowledge base packaged with Oracle Text, see
For more information about document services, see Chapter 8, "CTX_DOC Package"
Knowledge bases can be in any single-byte character set. Supplied knowledge bases are in WE8ISO8859P1. You can store an extended knowledge base in another character set such as US7ASCII.
ctxkbtc -user uname/passwd
[-name thesname1 [thesname2 ... thesname16]] [-revert] [-stoplist stoplistname] [-verbose] [-log filename]
Specify the user name and password for the administrator creating an extended knowledge base. This user must have write permission to the
Specify the names of the thesauri (up to 16) to be compiled with the knowledge base to create the extended knowledge base. The thesauri you specify must already be loaded with
ctxload with the "-
thescase Y" option
Reverts the extended knowledge base to the default knowledge base provided by Oracle Text.
Specify the name of the stoplist. Stopwords in the stoplist are added to the knowledge base as useless words that are prevented from becoming themes or contributing to themes. Add stopthemes after running this command using
Displays all warnings and messages, including non-Globalization Support messages, to the standard output.
Specify the log file for storing all messages. When you specify a log file, no messages are reported to standard out.
ctxkbtc, you must set the
NLS_LANG environment variable to match the database character set.
The user issuing
ctxkbtc must have write permission to the
ORACLE_HOME, because the program writes files to this directory.
Before being compiled, each thesaurus must be loaded into Oracle Text case sensitive with the "-
thescase Y" option in
ctxkbtc twice removes the previous extension.
ctxkbtc program has the following limitations:
When upgrading or downgrading your database to a different release, for theme indexing and related features to work correctly, Oracle recommends that you recompile your extended knowledge base in the new environment.
Before extending the knowledge base, you must terminate all server processes that have invoked any knowledge base-related Text functions during their lifetime.
There can be only one user extension for each language for each installation. Because a user extension affects all users at the installation, only the
CTXSYS user can extend the knowledge base.
In an Oracle RAC environment, the
ORACLE_HOME can either be shared between multiple nodes, or each node can have its own
ORACLE_HOME. The following requirements apply:
Before using any knowledge base-dependent functionality in any of the Oracle RAC nodes,
ctxkbtc must be run in every
ORACLE_HOME in the Oracle RAC environment.
ctxkbtc, the exact same input thesaurus content must be used in every
ORACLE_HOME in the Oracle RAC environment.
Terms are case sensitive. If a thesaurus has a term in uppercase, for example, the same term present in lowercase form in a document will not be recognized.
The maximum length of a term is 80 characters.
Disambiguated homographs are not supported.
The following constraints apply to thesaurus relations:
BTG and BTP are the same as BT. NTG and NTP are the same as NT.
Only preferred terms can have a BT, NTs or RTs.
If a term has no USE relation, it will be treated as its own preferred term.
If a set of terms are related by SYN relations, only one of them may be a preferred term.
An existing category cannot be made a top term.
There can be no cycles in BT and NT relations.
A term can have at most one preferred term and at most one BT. A term may have any number of NTs.
An RT of a term cannot be an ancestor or descendent of the term. A preferred term may have any number of RTs up to a maximum of 32.
The maximum height of a tree is 16 including the top term level.
When multiple thesauri are being compiled, a top term in one thesaurus should not have a broader term in another thesaurus.
Note:The thesaurus compiler tolerates some violations of the preceding rules. For example, if a term has multiple BTs, then the compiler ignores all but the last one it encounters.
Similarly, BTs between existing knowledge base categories result only in a warning message.
Oracle recommends that you do not set up extended storage bases with violations. Using extended storage bases containing violations can produce undesired results.
Extend the supplied knowledge base by compiling one or more thesauri with the Oracle Text knowledge base. The extended information can be application-specific terms and relationships. During theme analysis, the extended portion of the knowledge base overrides any terms and relationships in the knowledge base where there is overlap.
When extending the knowledge base, Oracle recommends that new terms be linked to one of the categories in the knowledge base for best results in theme proving when appropriate.
See Also:For complete description of the supplied knowledge base, see
If new terms are kept completely disjoint from existing categories, fewer themes from new terms will be proven. The result of this is poorer precision and recall with
ABOUT queries as well poor quality of gists and theme highlighting.
Link new terms to existing terms by making an existing term the broader term for the new terms.
You purchase a medical thesaurus
medthes containing a hierarchy of medical terms. The four top terms in the thesaurus are the following:
Anesthesia and Analgesia
Anti-Allergic and Respiratory System Agents
Anti-Inflammatory Agents, Antirheumatic Agents, and Inflammation Mediators
Antineoplastic and Immunosuppressive Agents
To link these terms to the existing knowledge base, add the following entries to the medical thesaurus to map the new terms to the existing health and medicine branch:
health and medicine NT Anesthesia and Analgesia NT Anti-Allergic and Respiratory System Agents NT Anti-Inflamammatory Agents, Antirheumatic Agents, and Inflamation Mediators NT Antineoplastic and Immunosuppressive Agents
Set your globalization support language environment variable to match the database character set. For example, if your database character set is WE8ISO8859P1 and you are using American English, set your
NLS_LANG as follows:
setenv NLS_LANG AMERICAN_AMERICA.WE8ISO8859P1
Assuming the medical thesaurus is in a file called med.thes, load the thesaurus as
ctxload as follows:
ctxload -thes -thescase y -name medthes -file med.thes -user ctxsys/ctxsys
To link the loaded thesaurus
medthes to the knowledge base, use
ctxkbtc as follows:
ctxkbtc -user ctxsys/ctxsys -name medthes
Extend theme functionality to languages other than English or French by loading your own knowledge base for any single-byte whitespace delimited language, including Spanish.
Theme functionality includes theme indexing,
ABOUT queries, theme highlighting, and the generation of themes, gists, and theme summaries with the
CTX_DOC PL/SQL package.
Extend theme functionality by adding a user-defined knowledge base. For example, you can create a Spanish knowledge base from a Spanish thesaurus.
To load your language-specific knowledge base, follow these steps:
Load your custom thesaurus using
Set NLS_LANG so that the language portion is the target language. The charset portion must be a single-byte character set.
Compile the loaded thesaurus using
ctxkbtc -user ctxsys/ctxsys -name my_lang_thes
This command compiles your language-specific knowledge base from the loaded thesaurus. To use this knowledge base for theme analysis during indexing and
ABOUT queries, specify the
NLS_LANG language as the
THEME_LANGUAGE attribute value for the
The following limitations hold for adding knowledge bases:
Oracle Text supplies knowledge bases in English and French only. You must provide your own thesaurus for any other language.
You can only add knowledge bases for languages with single-byte character sets. You cannot create a knowledge base for languages which can be expressed only in multibyte character sets. If the database is a multibyte universal character set, such as UTF-8, the NLS_LANG parameter must still be set to a compatible single-byte character set when compiling the thesaurus.
Adding a knowledge base works best for whitespace delimited languages.
You can have at most one knowledge base for each globalization support language.
Obtaining hierarchical query feedback information such as broader terms, narrower terms and related terms does not work in languages other than English and French. In other languages, the knowledge bases are derived entirely from your thesauri. In such cases, Oracle recommends that you obtain hierarchical information directly from your thesauri.
When multiple thesauri are to be compiled, precedence is determined by the order in which thesauri are listed in the arguments to the compiler, assumed to be most preferred first. A user-defined thesaurus always has precedence over the built-in knowledge base.
The following table lists the size limits associated with creating and compiling an extended knowledge base.
|Description of Parameter||Limit|
Number of RTs (from + to) for each term
Number of terms for each single hierarchy (for example, all narrower terms for a given top term)
Number of new terms in an extended knowledge base
Number of separate thesauri that can be compiled into a user extension to the KB
The Lexical Compiler (
ctxlc) is a command-line utility that enables you to create your own Chinese and Japanese lexicons (dictionaries). Such a lexicon may either be generated from a user-supplied word list or from the merging of a word list with the system lexicon for that language.
ctxlc creates the new lexicon in your current directory. The new lexicon consists of three files,
droli.dat. To change your system lexicon for Japanese or Chinese, overwrite the system lexicon with these files.
The Lexical Compiler can also generate wordlists from the system lexicons for Japanese and Chinese, enabling you to see their contents. These word lists go to the standard output and thus can be redirected into a file of your choice.
After overwriting the system lexicon, you need to re-create your indexes before querying them.
ctxlc has the following syntax:
ctxlc -ja | -zh [ -n ] -ics character_set -i input_file ctxlc -ja | -zh -ocs character_set [ > output_file ]
Specify the language of the lexicon to modify or create.
-ja indicates the Japanese lexicon;
-zh indicates the Chinese lexicon.
Specify the character set of the input file denoted by
-i input_file. input_file is the list of words, one word to a line, to use in creating the new lexicon.
Specify the file containing words to use in creating a new lexicon.
Specify the character set of the text file to be output.
-n to create a new lexicon that consists only of user-supplied words taken from input_file. If
-n is not specified, then the new lexicon consists of a merge of the system lexicon with input_file. Also, when
-n is not selected, a text file called
drolt.dat, is created in the current directory to enable you to inspect the contents of the merged lexicon without having to enter another
You can add up to 1,000,000 new words to a lexicon. However, creating a very large lexicon can reduce performance in indexing and querying. Performance is best when the lexicon character set is UTF-8. There is no performance impact on the Chinese or Japanese V-gram lexers, as they do not use lexicons.
Oracle recommends the following practices with regard to
Save your plain text dictionary file in your environment for emergency use.
When upgrading or downgrading your database to a different release, recompile your plain text dictionary file in the new environment so that the user lexicon will work correctly.
In this example, you create a new Japanese lexicon from the file
jadict.txt, a word list that uses the JA16EUC character set. Because you are not specifying
-n, the new lexicon is the result of merging
jadict.txt with the system Japanese lexicon. Then replace the existing Japanese lexicon with the new, merged one.
% ctxlc -ja -ics JA16EUC -i jadict.txt
This creates new files in the current directory:
% ls drold.dat drolk.dat droli.dat drolt.dat
The system lexicon files for Japanese and Chinese are named
.dat, where xx is either
JA (for Japanese) or
ZH (for Chinese). Rename the three new files and copy them to the directory containing the system Japanese lexicon.
% mv drold.dat droldJA.dat % mv drolk.dat drolkJA.dat % mv droli.dat droliJA.dat % cp *dat $ORACLE_HOME/ctx/data/jalx
This replaces the system Japanese lexicon with one that is a merge of the old system lexicon and your wordlist from
You can also use
ctxlc to get a dump of a system lexicon. This example dumps the Chinese lexicon to a file called
new_chinese_dict.txt in the current directory:
% ctxlc -zh -ocs UTF8 > new_chinese_dict.txt
This creates a file,
new_japanese.dict.txt, using the UTF8 character set, in the current directory.