DBMS_XDBT

The DBMS_XDBTpackage 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:

• Overview

• Security Model

• Operational Notes

• Summary of DBMS_XDBT Subprograms

See Also: Oracle XML DB Developer’s Guide

DBMS_XDBT Overview

The DBMS_XDBT package contains a set of package variables that describe the configuration settings for the index.

The DBMS_XDBT package can be used in the following ways:

• Customize the package to set up the appropriate configuration.

• Use the DROPPREFERENCES Procedure to drop any existing index preferences

• 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

DBMS_XDBT Security Model

Owned by XDB, the DBMS_XDBT package must be created by SYS or XDB. The EXECUTE privilege is granted to SYS or XDB. Subprograms in this package are executed using the privileges of the current user.

DBMS_XDBT Operational Notes

Configuration settings, or package variables, are available to customize the DBMS_XDBT package.

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.

Table 1 General Indexing Settings for Customizing DBMS_XDBT

Parameter	Default Value	Description
IndexName	XDB$CI	Name of the CONTEXT index.
IndexTablespace	XDB$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 ROWIDduring indexing. The LOG_DIRECTORY system parameter must be set already. NULL turn s off ROWIDlogging.

Table 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 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 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 5 Other Index Preference Settings for Customizing DBMS_XDBT

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

Table 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, orSYNC_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 orSYNC_BY_PENDING_COUNT_AND_TIME

Summary of DBMS_XDBT Subprograms

This table lists the DBMS_XDBT subprograms in alphabetical order and briefly describes them.

Table 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

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 theSyncInterval configuration parameter).
SYNC_BY_PENDING_COUNT_AND_TIME	A combination of both of the preceding options.

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_XDBTpackage 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.

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.

• TheUSER datastore procedure filters the incoming document; see CREATEDATASTOREPREF Procedure for more details.

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 IndexNameconfiguration 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.

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 lexerpreference 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.

CREATEPREFERENCES Procedure

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

Syntax

DBMS_XDBT.CREATEPREFERENCES;

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 SectiongroupPrefconfiguration 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_GROUPor the PATH_SECTION_GROUP; see the SectionGroupconfiguration setting.

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.

CREATESTORAGEPREF Procedure

This procedure creates a BASIC_STORAGEpreference 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_CLAUSEuses key compression.

CREATEWORLDLISTPREF Procedure

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

Syntax

DBMS_XDBT.CREATEWORDLISTPREF;

Usage Notes

• The name of the word list preference can be modified; see the WordlistPrefconfiguration setting. No other configuration settings are provided.

• FUZZY_MATCH and STEMMER attributes are set to AUTO (auto-language detection)

DROPPREFERENCES Procedure

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

Syntax

DBMS_XDBT.DROPPREFERENCES;