SQL/MP Query Guide

Selectivity and Cost Estimates
HP NonStop SQL/MP Query Guide—524488-003
5-21
Forcing Execution Plans
•
The query might not be able to benefit from future enhancements to SQL
•
Changes to the database structure (such as dropping an index) can require
recompilation when the option is in use
Therefore, make any occurrences of it easy to find and change, using one or more of
these alternatives:
•
Make sure the directive only applies to the statement and table intended. Return
the specified table to SYSTEM method directly after the statement.
•
Isolate this directive in its own section and perform it from the inline application
code.
•
Place all statements affected by this directive in separate modules, called as
services by other modules.
Verify the use of any of these options periodically to account for changes in data
distributions and volumes. Reevaluate their effectiveness with each new version of
SQL.