Estimating Statistics for Generating Execution Plans for Database Queries

摘要

A database system identifies missing statistics that is not available for processing database queries and determines the missing statistics. The database system generates execution plans for database queries. The database system requests certain statistical information for generating a database query. If the database system determines that the requested statistical information is not available, the database system stores information describing the requested statistical information as missing statistics. The missing statistics may identify one or more columns associated with tables processed by the database query. The database system performs statistical analysis of database tables to generate the missing statistics so that the statistical information is available for generating execution plans for subsequent queries. The database system may rank the missing statistics based on the number of times the missing statistics was identified by the database system while processing database queries.

主权项

1. A computer-implemented method for generating statistics for processing database queries, the method comprising:
receiving a plurality of database queries by a database system, the database queries processing data stored in database tables of the database system; identifying missing statistics while generating execution plans for database queries, the identifying comprising, for each of the plurality of database queries:
requesting a statistical information useful for generating an execution plan for a database query;determining that the requested statistical information is not available; andstoring information describing the requested statistical information as missing statistics, responsive to determining that the requested statistical information is not available; and performing statistical analysis to determine at least a subset of the identified missing statistics for use in generating execution plans for subsequent database queries.