Enables or disables the performance enhancements associated with exposed USING values in parameterized queries.
Field Group
Performance
Valid Settings
| Setting | Description |
|---|---|
| TRUE | Optimizer peek USING performance enhancements are disabled. |
| FALSE | Optimizer peek USING performance enhancements are enabled. |
Default
FALSE
Changes Take Effect
As soon as the request cache is purged.
Performance Implications
The Teradata Query Optimizer determines the most efficient way to execute an SQL request in the Teradata parallel environment. It generates several possible plans of action, which involve alternate methods of accessing and joining database tables to satisfy the request. The Optimizer evaluates the relative costs of each plan in terms of resource usage and speed of execution, then chooses the plan with the lowest cost. Plans that are sufficiently generic are cached for fast reuse by the Optimizer in similar situations.
For some parameterized queries, the Optimizer can generate better plans by "peeking" at the specific USING values (data parcels) in the queries. Because the plans are specific for the USING values, they are not cached, which in rare cases may have an adverse affect on performance. The DisablePeekUsing field allows you to disable this feature of the Optimizer if you suspect it is a problem.
Related Information
| For more information on… | See… |
|---|---|
| the request cache and query optimization | SQL Request and Transaction Processing, B035-1142. |
| parameterized queries | SQL Request and Transaction Processing, B035-1142. |