152 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

The DBMS_XDBT package can be used in the following fashion:


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 152-1 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 152-2 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 152-3 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 152-4 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 152-5 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 152-6 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



Summary of DBMS_XDBT Subprograms

Table 152-7 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 the SyncInterval 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_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.


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 Procedurefor 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 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.


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.


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 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.


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_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.


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)


DROPPREFERENCES Procedure

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

Syntax

DBMS_XDBT.DROPPREFERENCES;