Database system for executing parameter-sensitive query

摘要

A query is received. The query comprises a plural number of efficiency expressions. A key is generated for the query indicating a first selectivity region in multi-dimensional selectivity space comprising an array of selectivity regions arranged according to a grid with a number of dimensions equal to the plural number. The generated key is used to look up a stored query plan among a plurality of stored query plans. A stored query plan is executed for the query that is associated with a stored key determined to match the generated key.

主权项

1. A method in a data processing system that includes storage that stores data, and includes one or more processors configured to execute queries against the data, the method comprising:
storing a plurality of keys associated with a plurality of previous queries, the plurality of keys including a first key associated with a first previous query; receiving a query comprising a plural number of efficiency expressions; generating, based on the received query, a second key indicating a first selectivity region in a selectivity space comprising an array of selectivity regions arranged according to a grid with a number of dimensions equal to the plural number; comparing the second key to the plurality of keys; executing, based on the received query, a stored query plan associated with the first key on a condition that the first key is determined to match the second key; and executing, for the received query, a new query plan associated with the second key when the second key is determined to not match any stored key of the plurality of stored keys.