QUERY_REWRITE_ENABLED

Parameter type	String
Syntax	QUERY_REWRITE_ENABLED = {force | true | false}
Default value	false
Parameter class	Dynamic: ALTER SESSION, ALTER SYSTEM
Real Application Clusters	Multiple instances can have different values.

QUERY_REWRITE_ENABLED allows you to enable or disable query rewriting globally for the database.

Values:

• true

  Oracle costs the query with rewrite and without rewrite and chooses the method with the lower cost.

• false

  Oracle does not use rewrite.

• force

  Oracle always uses rewrite and does not evaluate the cost before doing so. Use force when you know that the query will always benefit from rewrite and when reduction in compile time is important.

To take advantage of query rewrite for a particular materialized view, you must enable query rewrite for that materialized view, and you must enable cost-based optimization.

See Also: Oracle9i Data Warehousing Guide for information on query rewrite of materialized views Oracle9i Database Performance Tuning Guide and Reference and "OPTIMIZER_MODE" for information on cost-based optimization