Method and apparatus for exploiting statistics on query...

Details Method and apparatus for exploiting statistics on query... Method and apparatus for exploiting statistics on query...

2008-04-22

2008-04-22

Al-Hashemi, Sana (Department: 2164)

Data processing: database and file management or data structures

Database design

Data structure types

C707S793000, C707S793000, C707S793000

Reexamination Certificate

active

07363289

ABSTRACT:
A method for evaluating a user query on a relational database having records stored therein, a workload made up of a set of queries that have been executed on the database, and a query optimizer that generates a query execution plan for the user query. Each query plan includes a plurality of intermediate query plan components that verify a subset of records from the database meeting query criteria. The method accesses the query plan and a set of stored intermediate statistics for records verified by query components, such as histograms that summarize the cardinality of the records that verify the query component. The method forms a transformed query plan based on the selected intermediate statistics (possibly by rewriting the query plan) and estimates the cardinality of the transformed query plan to arrive at a more accurate cardinality estimate for the query. If additional intermediate statistics are necessary, a pool of intermediate statistics may be generated based on the queries in the workload by evaluating the benefit of a given statistic over the workload and adding intermediate statistics to the pool that provide relatively great benefit.

REFERENCES:
patent: 6393419 (2002-05-01), Novak et al.
patent: 6529901 (2003-03-01), Chaudhuri et al.
patent: 6618719 (2003-09-01), Andrei
patent: 6732110 (2004-05-01), Rjaibi et al.
patent: 6754652 (2004-06-01), Bestgen et al.

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