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US 2006/0218128 A1Published application
Building database statistics across a join network using skew values
AssigneeInternational Business Machines Corporation
InventorBrian Muras
Life of this patent
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Abstract
An apparatus, program product and method that build column statistics utilizing at least one skew value. The column statistics built using skew values, instead of column statistics built only through random sampling, may be used to more accurately reflect skew values across join networks, and thus enable a query optimizer to better select an access plan that is optimal under current runtime conditions.
Claims18
A method of building database statistics, the method comprising:
- (a) building a first column statistic for a first column in a first table, including detecting at least one skew value in the first column statistic;
- and
- (b) using at least one detected skew value to build a second column statistic for a second column in a second table that is likely to be joined with the first column in a database query.
An apparatus, comprising:
- (a) at least one processor;
- (b) a memory;
- and
- (c) program code resident in the memory and configured to be executed by the at least one processor to build database statistics, the program code configured to build a first column statistic for a first column in a first table, including detecting at least one skew value in the first column statistic, and use at least one detected skew value to build a second column statistic for a second column in a second table that is likely to be joined with the first column in a database query.
1 more element
A program product, comprising:
- (a) program code configured to build database statistics by building a first column statistic for a first column in a first table, including detecting at least one skew value in the first column statistic, and using at least one detected skew value to build a second column statistic for a second column in a second table that is likely to be joined with the first column in a database query;
- and
- (b) a computer readable signal bearing medium bearing the program code.
Dependencies are inferred from the claim text.