CREATION OF PRE-FILTERS FOR MORE EFFICIENT X-PATH PROCESSING

• US 20090210383A1
• Filed: 02/18/2008
• Published: 08/20/2009
• Est. Priority Date: 02/18/2008
• Status: Active Grant

• Current Assignee: Domo, Inc.
• Original Assignee: International Business Machines Corporation
• Inventors: Seemann, Normen
• Granted Patent: US 7,996,444 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06F 16/8365 Query optimisation

Abstract

A system and method is provided for XML query processing includes an execution compiler for transforming an XML query into an executable XML query plan. A query rewrite processor performs query transformation on the XML query, the query transformations including transforming an XPath within said XML Query into a pre-filter. The XML query is then transformed into a transformed XML query which includes the pre-filter.

Claims

1. An XML query rewrite method comprising:

identifying an XPath within an XML query; and

transforming said XPath into a pre-filter of said XML query.

2. The method of claim 1 further comprising executing said pre-filter.

3. The method of claim 2 further comprising executing said XML query after said execution of said pre-filter.

4. The method of claim 3 further comprising eliminating data using said pre-filter before executing said XML query.

5. The method of claim 1 further comprising:

finding an index that matches said pre-filter.

6. The method of claim 1 wherein said transforming comprises performing a query transformation by transforming the expression:

g$i[e1]/e2

into the expression

$i[e1][e2]/e2.

where e1 is a filter and e2 is a deterministic XQuery expression.

7. The method of claim 1 further comprising:

subsequent to said transforming, applying said XML query to a sequence of XML items selected from a group consisting of;

a sequence of XML items extracted from one or more extensible markup language (XML) documents, a sequence of XML items supplied by an Internet service, a sequence of HTML items extracted from one or more hypertext markup language (HTML) documents, and a sequence of HTML items supplied by an Internet service.

8. An XML query rewrite method for processing an XML query, said XML query rewrite method comprising:

identifying an XPath within said XML query;

transforming said XPath into a pre-filter;

executing said pre-filter; and

executing said XML query after said execution of said pre-filter.

9. The method of claim 8 further comprising eliminating data using said pre-filter before executing said XML query.

10. The method of claim 8 further comprising finding an index that matches said pre-filter.

11. The method of claim 8 wherein said transforming comprises performing a query transformation by transforming the expression

$i[e1]/e2

into the expression

$i[e1][e2]/e2

where e1 is a filter and e2 is a deterministic XQuery expression.

12. The method of claim 8 further comprising:

subsequent to said transforming, applying said XML query to a sequence of XML items selected from a group consisting of;

a sequence of XML items extracted from one or more extensible markup language (XML) documents, a sequence of XML items supplied by an Internet service, a sequence of HTML items extracted from one or more hypertext markup language (HTML) documents, and a sequence of HTML items supplied by an Internet service.

13. An XML compilation processor comprising:

an execution compiler transforming an XML query into an executable XML query plan;

a query rewrite processor performing query transformation on said XML query, said query transformations including transforming an XPath within said XML Query into a pre-filter, said query rewrite processor also transforms said XML query into a transformed XML query including said pre-filter.

14. The XML compilation processor of claim 13 wherein said execution compiler eliminates data using said pre-filter before said XML query is executed.

15. The XML compilation processor of claim 13 wherein said query rewrite processor is adapted to perform said query transformation by transforming the expression

$i[e1]/e2

into the expression

$i[e1][e2]/e2

where e1 is a filter and e2 is a deterministic XQuery expression.

16. The XML compilation processor of claim 13 further comprising:

an index matcher for finding an index that matches said pre-filter.

17. The XML compilation processor of claim 13 further comprising:

textual XML query parser for providing a parsed XML query; and

query optimizer for optimizing data flow.

18. The XML compilation processor of claim 17 further comprising a data flow modeler for receiving said parsed XML query and producing an equivalent data flow model.

19. The XML compilation processor of claim 18 further comprising an execution compiler for compiling a data flow model into an executable XML query plan.

20. An article of manufacture for use in a computer system tangibly embodying computer instructions executable by said computer system to perform process steps for querying an XML document, said process steps comprising:

identifying an XPath within said XML query;

transforming said XPath into a pre-filter;

executing said pre-filter; and

executing said XML query after said execution of said pre-filter.

21. The article of manufacture of claim 20 wherein said process steps further comprise matching an index to said pre-filter.

22. The article of manufacture of claim 20 wherein said transforming comprises performing a query transformation which transforms the expression

$i[e1]/e2

into the expression

$i[e1][e2]/e2

where e1 is a filter and e2 is a deterministic XQuery expression.