QUERY_REWRITE_ENABLED

官方文檔中：

QUERY_REWRITE_ENABLED

Property	Description
Parameter type	String
Syntax	QUERY_REWRITE_ENABLED = { false | true | force }
Default value	If OPTIMIZER_FEATURES_ENABLE is set to 10.0.0 or higher, then true If OPTIMIZER_FEATURES_ENABLE is set to 9.2.0 or lower, then false
Modifiable	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:

• false

  Oracle does not use rewrite.

• true

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

• 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.