16.10 - DisablePeekUsing - Teradata Database

Teradata Database Utilities

Product
Teradata Database
Release Number
16.10
Published
June 2017
Language
English (United States)
Last Update
2018-04-26
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Purpose

Enables or disables the performance enhancements associated with exposed USING values in parameterized queries.

This field should be changed only under the direction of Teradata Support Center personnel.

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 Database 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 Topics

For more information on… See…
the request cache and query optimization SQL Request and Transaction Processing.
parameterized queries SQL Request and Transaction Processing.