ADD_INDEX

Use this procedure to add a subindex to a catalog index preference. Create this preference by naming one or more columns in the base table.

Because you create subindexes to improve the response time of structured queries, the column you add should be used in the structured_query clause of the CATSEARCH operator at query time.

Note:

Both CTXCAT and the use of CTXCAT grammar as an alternative grammar for CONTEXT queries is deprecated. Instead, Oracle recommends that you use the CONTEXT indextype, which can provide all the same functionality, except that it is not transactional. Near-transactional behavior in CONTEXT can be achieved by using SYNC(ON COMMIT) or, preferably, SYNC(EVERY [time-period]) with a short time period.

CTXCAT was introduced when indexes were typically a few megabytes in size. Modern, large indexes, can be difficult to manage with CTXCAT. The addition of index sets to CTXCAT can be achieved more effectively by the use of FILTER BY and ORDER BY columns, or SDATA, or both, in the CONTEXT indextype. CTXCAT is therefore rarely an appropriate choice. Oracle recommends that you choose the more efficient CONTEXT indextype.

Syntax

CTX_DDL.ADD_INDEX(
           set_name        IN VARCHAR2,
           column_list     IN VARCHAR2,
           storage_clause  IN VARCHAR2
);

set_name

Specify the name of the index set.

column_list

Specify a comma-delimited list of columns to index. At index time, any column listed here cannot have a NULL value in any row in the base table. If any row is NULL during indexing, then an error is raised.

Always ensure that your columns have non-NULL values before and after indexing.

Note: A column name in column_list must not be prefixed by the owner, schema or table name.

storage_clause

Specify a storage clause.

Example

Consider a table called AUCTION with the following schema:

create table auction(
  item_id number,
  title varchar2(100),
  category_id number,
  price number,
  bid_close date);

Assume that queries on the table involve a mandatory text query clause and optional structured conditions on category_id. Results must be sorted based on bid_close.

You can create a catalog index to support the different types of structured queries a user might enter.

To create the indexes, first create the index set preference then add the required indexes to it:

begin
  ctx_ddl.create_index_set('auction_iset');
  ctx_ddl.add_index('auction_iset','bid_close');
  ctx_ddl.add_index('auction_iset','category_id, bid_close');
end;

Create the combined catalog index with CREATE INDEX as follows:

create index auction_titlex on AUCTION(title) indextype is CTXCAT parameters
('index set auction_iset');

Querying

To query the title column for the word pokemon, enter regular and mixed queries as follows:

select * from AUCTION where CATSEARCH(title, 'pokemon',NULL)> 0;
select * from AUCTION where CATSEARCH(title, 'pokemon', 'category_id=99 order by
bid_close desc')> 0;

Notes

VARCHAR2 columns in the column list of a CTXCAT index of an index set cannot exceed 30 bytes.

Related Topics

• REMOVE_INDEX