Query optimization by specifying path-based predicate evaluation in a path-based query operator
US8161035B2 · kind B2 · utility
Assignee
Inventors
Key dates
| Filing date | Jun 4, 2009 |
| Grant date | Apr 17, 2012 |
| Priority date | — |
| Expiry date | Dec 30, 2029 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG06F16/24542
- WIPO fieldComputer technology
- WIPO sectorElectrical engineering
Abstract
The approaches described herein provide an efficient way for a database server to process certain kinds of queries over XML data stored in an object-relational database that require the evaluation of a predicate expression with one or more path-based operands. A predicate expression part of a XQuery or SQL WHERE clause that returns a boolean value. A database server first determines whether the query qualifies for this particular kind of optimization, then rewrites the query using an enhanced query operator syntax for specifying the predicate expression to be evaluated. The enhanced query operator subsumes the work of a second path-based query operator, resulting in the suppression of the WHERE EXISTS subquery. The rewritten query operator is used to generate a query execution plan that provides for several query execution optimizations.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.