167 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.

Overview

The DBMS_XDBT package can be used in the following fashion:

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

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 167-1 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 `ROWID` during indexing. The `LOG_DIRECTORY` system parameter must be set already. `NULL t`urn s off `ROWID` logging.

Table 167-2 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 167-3 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 167-4 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 167-5 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 167-6 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 167-7 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 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 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;