STATIC DATA CACHING FOR QUERIES WITH A CLAUSE THAT REQUIRES MULTIPLE ITERATIONS TO EXECUTE

摘要

Techniques are described herein to generate and to execute a query execution plan using static data buffering. After receiving a query with a clause that requires multiple iterations to execute, a database management system (DBMS) generates a plurality of plans that vary the order in which the database operations are executed. Within each plan, the DBMS identifies sets of rows within that plan that contain static data during execution of the query. Then, an additional step is added to each plan that includes loading the static set of rows in a database buffer cache. One or more database operations, from an iteration other than the first iteration, may be performed against the cached static set of rows. For each plan generated in this manner, a cost analysis model is applied, and the plan with the lowest estimated computational cost is selected for use as the query execution plan.

主权项

1. A method comprising:
receiving a query with a clause that requires multiple iterations to execute; prior to executing the query, determining, based on the query, one or more database operations that are:
performed in more than one iteration, andat least partially performed against a static set of rows, said static set of rows being static during execution of the query; while executing the query,
loading said static set of rows into a database buffer cache; andperforming at least one iteration other than a first iteration against the buffered static set of rows.