Adaptive Server can capture query text and save an abstract plan for a query in a new system table called sysqueryplans. Using a rapid hashing method, incoming SQL queries can be compared to stored query text, and if a match is found, the saved abstract plan is used to execute the query.
An abstract plan describes the execution plan for a query using a language created for that purpose. This language contains operators to specify the choices and actions that can be generated by the optimizer. For example, to specify an index scan on the titles table, using the index title_id_ix, the abstract plan says:
( i_scan title_id_ix titles)
Abstract plans provide a means for System Administrators and performance tuners to protect the overall performance of a server from changes to query plans. Changes in query plans can arise due to:
Adaptive Server software upgrades that affect optimizer choices
New Adaptive Server features that change query plans
Changing tuning options such as the parallel degree, table partitioning, or indexing
Other uses include:
The ability to look for specific types of plans, such as table scans or reformatting
The ability to determine which plans use particular indexes
The ability to specify full or partial plans for poorly-performing queries.
For more information, see Chapter 21, “Introduction to Abstract Plans,” in the Performance and Tuning Guide.
