CREATE_PREFERENCE

Creates a preference in the Text data dictionary.

Specify preferences in the parameter string of CREATE INDEX or ALTER INDEX .

Caution: CTX_DDL.CREATE_PREFERENCE does not respect the current schema as set by ALTER SESSION SET current_schema. Therefore, if you need to create or delete a preference owned by another user, then you must explicitly state this, and you must have the CREATE ANY TABLE system privilege.

Syntax

CTX_DDL.CREATE_PREFERENCE(preference_name  in varchar2,
                          object_name      in varchar2);

preference_name

Specify the name of the preference to be created.

object_name

Specify the name of the preference type.

See Also: For a complete list of preference types and their associated attributes, see Oracle Text Indexing Elements

Examples

Creating Text-only Index

The following example creates a lexer preference that specifies a text-only index. It does so by creating a BASIC_LEXER preference called my_lexer with CTX_DDL.CREATE_PREFERENCE. It then calls CTX_DDL.SET_ATTRIBUTE twice, first specifying YES for the INDEX_TEXT attribute, then specifying NO for the INDEX_THEMES attribute.

begin
ctx_ddl.create_preference('my_lexer', 'BASIC_LEXER');
ctx_ddl.set_attribute('my_lexer', 'INDEX_TEXT', 'YES');
ctx_ddl.set_attribute('my_lexer', 'INDEX_THEMES', 'NO');
end;

Specifying File Data Storage

The following example creates a data storage preference called mypref that tells the system that the files to be indexed are stored in an Oracle directory object. The example then uses CTX_DDL.SET_ATTRIBUTE to set the DIRECTORY attribute to the directory /docs.

begin
ctx_ddl.create_preference('mypref', 'DIRECTORY_DATASTORE');
ctx_ddl.set_attribute('mypref', 'DIRECTORY', '/docs');
end;

See Also: For more information about data storage, see “Datastore Types”

Creating Primary/Detail Relationship

Use CTX_DDL.CREATE_PREFERENCE to create a preference with DETAIL_DATASTORE. Use CTX_DDL.SET_ATTRIBUTE to set the attributes for this preference. The following example shows how this is done:

begin
ctx_ddl.create_preference('my_detail_pref', 'DETAIL_DATASTORE');
ctx_ddl.set_attribute('my_detail_pref', 'binary', 'true');
ctx_ddl.set_attribute('my_detail_pref', 'detail_table', 'my_detail');
ctx_ddl.set_attribute('my_detail_pref', 'detail_key', 'article_id');
ctx_ddl.set_attribute('my_detail_pref', 'detail_lineno', 'seq');
ctx_ddl.set_attribute('my_detail_pref', 'detail_text', 'text');
end;

See Also: For more information about primary/detail, see “DETAIL_DATASTORE”

Specifying Storage Attributes

The following examples specify that the index tables are to be created in the foo tablespace with an initial extent of 1K:

begin
ctx_ddl.create_preference('mystore', 'BASIC_STORAGE');
ctx_ddl.set_attribute('mystore', 'I_TABLE_CLAUSE',
                        'tablespace foo storage (initial 1K)');
ctx_ddl.set_attribute('mystore', 'K_TABLE_CLAUSE',
                        'tablespace foo storage (initial 1K)');
ctx_ddl.set_attribute('mystore', 'R_TABLE_CLAUSE',
                        'tablespace foo storage (initial 1K)');
ctx_ddl.set_attribute('mystore', 'S_TABLE_CLAUSE',
                        'tablespace foo storage (initial 1K)');
ctx_ddl.set_attribute('mystore', 'N_TABLE_CLAUSE',
                        'tablespace foo storage (initial 1K)');
ctx_ddl.set_attribute('mystore', 'I_INDEX_CLAUSE',
                        'tablespace foo storage (initial 1K)');
end;

Note: If S_TABLE_CLAUSE is specified for a storage preference in an index without SDATA, then it has no effect on the index, and the index creation will still succeed.

See Also: Storage Types

Creating Preferences with No Attributes

When you create preferences with types that have no attributes, you need only create the preference, as in the following example which sets the filter to the NULL_FILTER:

begin
ctx_ddl.create_preference('my_null_filter', 'NULL_FILTER');
end;

Specifying BIGRAM Mode for Japanese VGRAM Lexer

The following example creates a Japanese VGRAM lexer preference that specifies the BIGRAM mode of operation for the Japanese queries:

begin
ctx_ddl.create_preference('jp_lexer','JAPANESE_VGRAM_LEXER');
ctx_ddl.set_attribute('jp_lexer','BIGRAM','TRUE');
end;

/* create the index */
create index jp_idx on jp_doc(text) indextype is ctxsys.context
  parameters('lexer jp_lexer');

SET_ATTRIBUTE DROP_PREFERENCE CREATE INDEX ALTER INDEX Oracle Text Indexing Elements