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DBMS_XDBT

The DBMS_XDBT package provides a convenient mechanism for administrators to set up a CONTEXT index on the Oracle XML DB hierarchy. The package contains procedures to create default preferences, create the index and set up automatic synchronization of the CONTEXT index

The DBMS_XDBT package also contains a set of package variables that describe the configuration settings for the index. These are intended to cover the basic customizations that installations may require, but is by no means a complete set.

This chapter contains the following topics:

• Using DBMS_XDBT
  • Overview
  • Operational Notes
• Summary of DBMS_XDBT Subprograms

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Using DBMS_XDBT

• Overview
• Operational Notes

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Overview

The DBMS_XDBT package can be used in the following fashion:

• Customize the package to set up the appropriate configuration.
• Drop any existing index preferences using the DROPPREFERENCES Procedure procedure.
• Create new index preferences using the CREATEPREFERENCES Procedure procedure.
• Create the CONTEXT index using the CREATEINDEX Procedure procedure.
• Set up automatic synchronization of the index using the CONFIGUREAUTOSYNC Procedure procedure.

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Operational Notes

The DBMS_XDBT package can be customized by using a PL/SQL procedure or an anonymous block to set the relevant package variables, configuration settings, and then execute the procedures. A more general approach would be to introduce the appropriate customizations by modifying this package in place, or as a copy. The system must be configured to use job queues, and the jobs can be viewed through the USER_JOBS catalog views. This section describes the configuration settings, or package variables, available to customize the DBMS_XDBT package.

Table 111-1  General Indexing Settings for Customizing DBMS_XDBT

Parameter	Default Value	Description
IndexName	XDB$CI	The name of the CONTEXT index.
IndexTablespace	XDB$RESINFO	Tablespace used by tables and indexes comprising the CONTEXT index.
IndexMemory	128M	Memory used by index creation and SYNC; less than or equal to the MAX_INDEX_MEMORY system parameter (see the CTX_ADMIN package).
LogFile	'XdbCtxLog'	The log file used for ROWID during indexing. The LOG_DIRECTORY system parameter must be set already. NULL turn s off ROWID logging.

Table 111-2  Filtering Settings for Customizing DBMS_XDBT

Parameter	Default Value	Description
SkipFilter_Types	image/%, audio/%, video/%, model/%	List of mime types that should not be indexed.
NullFilter_Types	text/plain, text/html, text/xml	List of mime types that do not need to use the INSO filter. Use this for text-based documents.
FilterPref	XDB$CI_FILTER	Name of the filter preference.

Table 111-3  Stoplist Settings for Customizing DBMS_XDBT

Parameter	Default Value	Description
StoplistPref	XDB$CI_STOPLIST	Name of the stoplist.
StopWords	0..9; 'a'..'z'; 'A'..'Z'	List of stopwords, in excess of CTXSYS.DEFAULT_STOPLIST.

Table 111-4  Sectioning and Section Group Settings for Customizing DBMS_XDBT

Parameter	Default Value	Description
SectionGroup	HTML_SECTION_GROUP	Default sectioner. Use PATH_SECTION_GROUP or AUTO_SECTION_GROUP if repository contains mainly XML documents.
SectiongroupPref	XDB$CI_SECTIONGROUP	Name of the section group.

Table 111-5  Other Index Preference Settings for Customizing DBMS_XDBT

Parameter	Default Value	Description
DatastorePref	XDB$CI_DATASTORE	The name of the datastore preference.
StoragePref	XDB$CI_STORAGE	The name of the storage preference.
WordlistPref	XDB$CI_WORDLIST	The name of the wordlist preference.
DefaultLexerPref	XDB$CI_DEFAULT_LEXER	The name of the default lexer preference.

Table 111-6  SYNC (CONTEXT Synchronization) Settings for Customizing DBMS_XDBT

Parameter	Default Value	Description
AutoSyncPolicy	SYNC_BY_PENDING_COUNT	Indicates when the index should be SYNCed. One of SYNC_BY_PENDING_COUNT, SYNC_BY_TIME, or SYNC_BY_PENDING_COUNT_AND_TIME.
MaxPendingCount	2	Maximum number of documents in the CTX_USER_PENDING queue before an index SYNC is triggered. Only if the AutoSyncPolicy is SYNC_BY_PENDING_COUNT or SYNC_BY_PENDING_COUNT_AND_TIME.
CheckPendingCountInterval	10 minutes	How often, in minutes, the pending queue should be checked. Only if the AutoSyncPolicy is SYNC_BY_PENDING_COUNT or SYNC_BY_PENDING_COUNT_AND_TIME.
SyncInterval	60 minutes	Indicates how often, in minutes, the index should be SYNCed. Only if the AutoSyncPolicy is SYNC_BY_TIME or SYNC_BY_PENDING_COUNT_AND_TIME

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Summary of DBMS_XDBT Subprograms

Table 111-7  DBMS_XDBT Package Subprograms

Subprogram	Description
CONFIGUREAUTOSYNC Procedure	Configures the CONTEXT index for automatic maintenance, SYNC
CREATEDATASTOREPREF Procedure	Creates a USER datastore preference for the CONTEXT index
CREATEFILTERPREF Procedure	Creates a filter preference for the CONTEXT index
CREATEINDEX Procedure	Creates the CONTEXT index on the XML DB hierarchy
CREATELEXERPREF Procedure	Creates a lexer preference for the CONTEXT index
CREATEPREFERENCES Procedure	Creates preferences required for the CONTEXT index on the XML DB hierarchy
CREATESECTIONGROUPPREF Procedure	Creates a storage preference for the CONTEXT index
CREATESTOPLISTPREF Procedure	Creates a section group for the CONTEXT index
CREATESTORAGEPREF Procedure	Creates a wordlist preference for the CONTEXT index
CREATEWORLDLISTPREF Procedure	Creates a stoplist for the CONTEXT index
DROPPREFERENCES Procedure	Drops any existing preferences

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CONFIGUREAUTOSYNC Procedure

This procedure sets up jobs for automatic SYNCs of the CONTEXT index.

Syntax

DBMS_XDBT.CONFIGUREAUTOSYNC;

Usage Notes

• The system must be configured for job queues for automatic synchronization. The jobs can be viewed using the USER_JOBS catalog views
• The configuration parameter AutoSyncPolicy can be set to choose an appropriate synchronization policy.

The synchronization can be based on one of the following:

Sync Basis	Description
SYNC_BY_PENDING_COUNT	The SYNC is triggered when the number of documents in the pending queue is greater than a threshold (See the MaxPendingCount configuration setting). The pending queue is polled at regular intervals (See the CheckPendingCountInterval configuration parameter) to determine if the number of documents exceeds the threshold.
SYNC_BY_TIME	The SYNC is triggered at regular intervals. (See the SyncInterval configuration parameter).
SYNC_BY_PENDING_COUNT_AND_TIME	A combination of both of the preceding options.

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CREATEDATASTOREPREF Procedure

This procedure creates a user datastore preference for the CONTEXT index on the XML DB hierarchy.

Syntax

DBMS_XDBT.CREATEDATASTOREPREF;

Usage Notes

• The name of the datastore preference can be modified; see the DatastorePref configuration setting.
• The default USER datastore procedure also filters the incoming document. The DBMS_XDBT package provides a set of configuration settings that control the filtering process.
• The SkipFilter_Types array contains a list of regular expressions. Documents with a mime type that matches one of these expressions are not indexed. Some of the properties of the document metadata, such as author, remain unindexed.
  • The NullFilter_Types array contains a list of regular expressions. Documents with a mime type that matches one of these expressions are not filtered; however, they are still indexed. This is intended to be used for documents that are text-based, such as HTML, XML and plain-text.
  • All other documents use the INSO filter through the IFILTER API.

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CREATEFILTERPREF Procedure

This procedure creates a NULL filter preference for the CONTEXT index on the XML DB hierarchy.

Syntax

DBMS_XDBT.CREATEFILTERPREF;

Usage Notes

• The name of the filter preference can be modified; see FilterPref configuration setting.
• The USER datastore procedure filters the incoming document; see CREATEDATASTOREPREF Procedure for more details.

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CREATEINDEX Procedure

This procedure creates the CONTEXT index on the XML DB hierarchy.

Syntax

DBMS_XDBT.CREATEINDEX;

Usage Notes

• The name of the index can be changed; see the IndexName configuration setting.
• Set the LogFile configuration parameter to enable ROWID logging during index creation.
• Set the IndexMemory configuration parameter to determine the amount of memory that index creation, and later SYNCs, will use.

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CREATELEXERPREF Procedure

This procedure creates a BASIC lexer preference for the CONTEXT index on the XML DB hierarchy.

Syntax

DBMS_XDBT.CREATELEXERPREF;

Usage Notes

• The name of the lexer preference can be modified; see LexerPref configuration setting. No other configuration settings are provided.
• MultiLexer preferences are not supported.
• Base letter translation is turned on by default.

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CREATEPREFERENCES Procedure

This procedure creates a set of default preferences based on the configuration settings.

Syntax

DBMS_XDBT.CREATEPREFERENCES;

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CREATESECTIONGROUPPREF Procedure

This procedure creates a section group for the CONTEXT index on the XML DB hierarchy.

Syntax

DBMS_XDBT.CREATESECTIONGROUPPREF;

Usage Notes

• The name of the section group can be changed; see the SectiongroupPref configuration setting.
• The HTML sectioner is used by default. No zone sections are created by default. If the vast majority of documents are XML, consider using the AUTO_SECTION_GROUP or the PATH_SECTION_GROUP; see the SectionGroup configuration setting.

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CREATESTOPLISTPREF Procedure

This procedure creates a stoplist for the CONTEXT index on the XML DB hierarchy.

Syntax

DBMS_XDBT.CREATESTOPLISTPREF;

Usage Notes

• The name of the stoplist can be modified; see the StoplistPref configuration setting.
• Numbers are not indexed.
• The StopWords array is a configurable list of stopwords. These are meant to be stopwords in addition to the set of stopwords in CTXSYS.DEFAULT_STOPLIST.

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CREATESTORAGEPREF Procedure

This procedure creates a BASIC_STORAGE preference for the CONTEXT index on the XML DB hierarchy.

Syntax

DBMS_XDBT.CREATESTORAGEPREF;

Usage Notes

• The name of the storage preference can be modified; see the StoragePref configuration setting.
• A tablespace can be specified for the tables and indexes comprising the CONTEXT index; see the IndexTablespace configuration setting.
• Prefix and Substring indexing are not turned on by default.
• The I_INDEX_CLAUSE uses key compression.

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CREATEWORLDLISTPREF Procedure

This procedure creates a wordlist preference for the CONTEXT index on the XML DB hierarchy.

Syntax

DBMS_XDBT.createWordlistPref;

Usage Notes

• The name of the wordlist preference can be modified; see the WordlistPref configuration setting. No other configuration settings are provided.
• FUZZY_MATCH and STEMMER attributes are set to AUTO (auto-language detection)

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DROPPREFERENCES Procedure

This procedure drops any previously created preferences for the CONTEXT index on the XML DB hierarchy.

Syntax

DBMS_XDBT.DROPPREFERENCES;