Query Explain Plan

With query explain plan, formerly known as query expression feedback, you can obtain an execution plan of a Text query before actually issuing the query. Oracle returns the explain plan information in a table, from which you can construct a parse tree.

In interMedia Text 8.1, this feature has been renamed from query expression feedback to query explain plan. Query explain plan should not be confused with hierarchical query feedback, which is a new, different feature.

The user interface for query explain plan has changed in the following ways:

• the procedure CTX_QUERY.FEEDBACK has been renamed to CTX_QUERY.EXPLAIN

• in CTX_QUERY.EXPLAIN, you specify index name rather than policy

• the FEEDBACK_ID column in the result table has been renamed to EXPLAIN_ID

• the OPERATION column in the explain table has new ABOUT operation value

• FIRST_NEXT_DOC and MAX_DOC operation column values have been removed

• the numbers associated with WEIGHT and THRESHOLD have moved from OPTIONS column to the OBJECT_NAME column.

  See Also: For more information on the syntax of CTX_QUERY.EXPLAIN and the structure of the explain table, see Oracle8i interMedia Text Reference.

Obtaining Explain Information

You use the CTX_QUERY.EXPLAIN to obtain expression feedback. The procedure for obtaining this information has not changed from pre-8.1 to 8.1. You must do the following:

1. Create the explain table.

2. Execute CTX_QUERY.EXPLAIN

3. Retrieve data from explain table.

4. Optionally, construct expansion tree from table information.

You must use the new 8.1 explain syntax when you code the first three steps.

The way you construct and expansion tree from the explain table in step 4 is the same as in pre-8.1

See Also: For examples on constructing the expansion tree, see the CTX_QUERY.EXPLAIN command syntax in the Oracle8i interMedia Text Reference.