Changing the compression level of query plans
In an embodiment, a query plan is compressed to data in a cache at a high compression level if a runtime of a query that the query plan implements is greater than a high time threshold. The query plan is compressed to the data in the cache at a medium compression level if the runtime of the query that the query plan implements is less than the high time threshold and greater than a low time threshold. The query plan is stored to the data in the cache at an uncompressed level if the runtime of the query that the query plan implements is less than the low time threshold.
1. A computer-implemented method, comprising:
generating a plurality of query plans, each plan for executing a respective query against data in a database,
with respect to each query plan of said plurality of query plans, selectively determining whether the respective query plan should be stored to data in a cache in a compressed form;
with respect to each query plan of said plurality of query plans for which it is selectively determined that the respective query plan should be stored to data in a cache in compressed form, storing the query plan to data in the cache in a compressed form; and
with respect to each query plan of said plurality of query plans for which it is selectively determined that the respective query plan should not be stored to data in a cache in compressed form, storing the query plan to data in the cache in an uncompressed form;
storing uncompressed metadata to the cache that describes the data in the cache that is compressed;
receiving a query against data in said database; and
selecting the query plan with the uncompressed metadata that meets a criteria specified by the query, in response to receiving the query.
2. A computer-implemented method, comprising:
generating a plurality of query plans, each plan for executing a respective query against data in a database,
with respect to each query plan of said plurality of query plans, selectively determining whether the respective query plan should be stored to data in a cache in a compressed form;
with respect to each query plan of said plurality of query plans for which it is selectively determined that the respective query plan should be stored to data in a cache in compressed form, storing the query plan to data in the cache in a compressed form; and
with respect to each query plan of said plurality of query plans for which it is selectively determined that the respective query plan should not be stored to data in a cache in compressed form, storing the query plan to data in the cache in an uncompressed form;
wherein said selectively determining whether the respective query plan should be stored to data in a cache in a compressed form comprises making the selective determination using at least one parameter from: (a) an estimated runtime of the respective query plan; (b) an estimated frequency of execution of the respective query plan; (c) a cache utilization of said cache; (d) a memory utilization; (e) a concurrency level; and (f) a CPU utilization.