Join factorization of union/union all queries
US7644062B2 · kind B2 · utility
8Cited by
65References
20Claims
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Key dates
| Filing date | Mar 8, 2007 |
| Grant date | Jan 5, 2010 |
| Priority date | — |
| Expiry date | Jan 16, 2028 |
Classification
- Technology area (CPC Y)Emerging Cross-Sectional Technologies
- CPC primaryY10S707/99932
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
Under a type of query transformation referred to herein as join factorization, the branches of an UNION/UNION ALL query that join a common table are combined to reduce accesses to the common table. The transformation can be expressed as (T1 join T2) union all (T1 join T3)=T1 join (T2 union all T3), where T1, T2 and T3 are three tables. A given query may be rewritten in many alternate ways using join factorization. Evaluating each alternative can be expensive. Therefore, the alternatives are generated and evaluated in a way that minimizes the cost of evaluating the alternatives.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.