Database query

摘要

Mechanisms for performing database queries are provided. With these mechanisms, in response to a query request, a query plan intended for minimum query response time and a query plan intended for minimum query total time for the query request are obtained execution of the minimum query response time query plan and the minimum query total time query plan is started. Before the execution of the minimum query total time query plan reaches a specified point, an initial query result obtained from the execution of the minimum query response time query plan is output. In response to the execution of the minimum query total time query plan reaching the specified point, continuing the execution of the minimum query total time query plan to output remaining query results.

主权项

1. A method of database query, comprising:
in response to a query request, obtaining a first query plan for minimum query response time and a second query plan for minimum query total time for the query request; starting execution of the first query plan and execution of the second query plan at substantially a same time; outputting, before execution of the second query plan reaches a specified point, an initial query result obtained from execution of the first query plan; and in response to execution of the second query plan reaching the specified point, continuing execution of the second query plan to output remaining query results, wherein the first query plan is a query plan using a nested loop join operation, the second query plan is a query plan using a hash join operation and the specified point is a point where a construction stage of the hash join operation ends, wherein continuing execution of the second query plan comprises: performing operation of a detection stage of the second query plan using the hash join operation, from a first record on which the nested loop join operation has not been performed in a driving table of the first query plan.