Invention Grant
- Patent Title: Embracing and exploiting data skew during a join or groupby
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Application No.: US14509336Application Date: 2014-10-08
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Publication No.: US09672248B2Publication Date: 2017-06-06
- Inventor: Gopi K. Attaluri , Vijayshankar Raman
- Applicant: International Business Machines Corporation
- Applicant Address: US NY Armonk
- Assignee: INTERNATIONAL BUSINESS MACHINES CORPORATION
- Current Assignee: INTERNATIONAL BUSINESS MACHINES CORPORATION
- Current Assignee Address: US NY Armonk
- Agency: Edell, Shapiro & Finnan, LLC
- Agent Erik K. Johnson
- Main IPC: G06F17/30
- IPC: G06F17/30

Abstract:
A hybrid approach for performing a join in a database includes: obtaining a distribution of data values in a join column of an inner table; using the distribution, identifying one or more data ranges containing skew; for each data range identified as containing skew, performing, by the processor, the join operation using a skew specific join scheme; and for each data range not identified as containing skew, performing, by the processor, the join operation using a non-skew specific join scheme. One skew specific join scheme involves a compact array table, a highly populated array that represents the range of values that the inner table join column contains. One non-skew specific join scheme involves a compact hash table, an optimized hash table that allows high load factors with a small memory overhead. In combining multiple join techniques, joins may be performed more efficiently for skewed and non-skewed data.
Public/Granted literature
- US20160103879A1 EMBRACING AND EXPLOITING DATA SKEW DURING A JOIN OR GROUPBY Public/Granted day:2016-04-14
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