Efficient query processing on ordered views

• US 9,471,630 B2
• Filed: 03/06/2012
• Issued: 10/18/2016
• Est. Priority Date: 03/06/2012
• Status: Expired due to Fees

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Gupte, Ajaykumar B., Murthy, Raghupathi K., Zuzarte, Joaquim A.
• Primary Examiner(s): Liao, Jason
• Assistant Examiner(s): Brooks, David T
• Application Number:
  US13/413,535
• Publication Number:
  US 20130238637A1
• Time in Patent Office: 1,687 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: G06F 16/24534 Query rewriting; Transformation
• CPC Class Codes: G06F 16/24535 of sub-queries or views
• CPC Class Codes: G06F 16/24556 Aggregation; Duplicate elimination

Abstract

The efficient query processing on ordered views includes: obtaining a view definition for a view for database data; obtaining a query to be executed on the database data; identifying any columns in the view that are unnecessary for the query; after processing any predicates of the query, identifying any sorts in the view definition that are unnecessary or redundant in the query; rewriting the query to eliminate the unnecessary columns and unnecessary and redundant sorts; and executing the rewritten query without materializing the view. Thus, the query is rewritten in a way that avoids materializing the view and eliminates duplicate or unnecessary sorts. This reduces the number of rows to be sorted and eliminates unnecessary columns from materialization. These reductions lead to resource savings, including memory, temporary table space required for sorting, and CPU resources.

Claims

1. A method for efficient query processing on ordered views by a computing device comprising a processor, comprising:

processing a query for database data in a database system that does not support view definitions containing a sorting clause, the query processed against an ordered view without materialization of the ordered view, wherein the ordered view comprises operations directed to at least one database table, wherein a view definition that defines the ordered view comprises at least one sorting clause, wherein the view definition comprising the at least one sorting clause is not supported by the database system by;

obtaining the view definition for the ordered view;

obtaining the query to be executed on the database data, wherein the query comprises operations directed to the ordered view;

identifying any columns in the view definition that are unnecessary for the query;

after processing any predicates of the query, identifying any sorts in the view definition that are unnecessary or redundant in the query, wherein the sorts in the view definition are defined by the at least one sorting clause, and are not supported by the database system; and

rewriting the query to eliminate the unnecessary columns, and unnecessary or redundant sorts, wherein the query is rewritten to comprise operations directed only to the at least one database table, wherein the resulting rewritten query is processed efficiently due to;

i) the elimination of the unnecessary columns;

ii) the elimination of unnecessary or redundant sorts;

iii) an effective processing of the ordered view, comprising the at least one sorting clause, without materialization; and

iv) fewer rows of data returned when the rewritten query is executed.

2. The method of claim 1, further comprising:

executing the rewritten query.

3. The method of claim 1, wherein the identifying any sorts in the view definition that are unnecessary or redundant in the query comprises:

processing the query predicates;

determining that the view definition comprises one or more view sorts;

determining whether the view sort is used in the query or affects query results; and

in response to determining that the view sort is not used in the query and does not affect the query results, not applying the view sort to the query.

4. The method of claim 1, wherein the identifying any sorts in the view definition that are unnecessary or redundant in the query comprises:

processing the query predicates;

determining that the view definition comprises one or more view sorts;

determining whether the view sort is used in the query or affects query results;

in response to determining that the view sort is used in the query or does affect the query results, determining whether the query comprises one or more sorts; and

in response to determining that the query does not comprise any sorts, applying the view sort to the query.

5. The method of claim 1, wherein the identifying any sorts in the view definition that are unnecessary or redundant in the query comprises:

processing the query predicates;

determining that the view definition comprises one or more view sorts;

determining whether the view sort is used in the query or affects query results;

in response to determining that the view sort is used in the query or does affect the query results, determining whether the query comprises one or more query sorts;

in response to determining that the query comprises one or more query sorts, determining whether the view sort matches the query sort; and

in response to determining that the view sort matches the query sort, not applying the view sort to the query.

6. The method of claim 5, wherein the identifying any sorts in the view definition that are unnecessary or redundant in the query further comprises:

in response to determining that the view sort does not match the query sort, not applying the view sort to the query.

7. The method of claim 5, wherein the identifying any sorts in the view definition that are unnecessary or redundant in the query further comprises:

in response to determining that the view sort does not match the query sort, building a composite sort from the view sort and the query sort; and

applying the composite sort to the query.

8. A non-transitory computer readable storage media, not including signals per se, containing a computer program product for efficient query processing on ordered views comprising:

the computer readable storage media having computer readable program code embodied therewith, the computer readable program code configured to;

process a query for database data in a database system that does not support view definitions containing a sorting clause, the query processed against an ordered view, without materialization of the ordered view, wherein the ordered view comprises operations directed to at least one database table, wherein a view definition that defines the ordered view comprises at least one sorting clause, wherein the view definition comprising the at least one sorting clause is not supported by the database system by;

obtaining the view definition for the ordered view;

obtaining the query to be executed on the database data, wherein the query comprises operations directed to the ordered view;

identifying any columns in the view definition that are unnecessary for the query;

after processing any predicates of the query, identifying any sorts in the view definition that are unnecessary or redundant in the query, wherein the sorts in the view definition are defined by the at least one sorting clause, and are not supported by the database system; and

rewriting the query to eliminate the unnecessary columns, and unnecessary or redundant sorts, wherein the query is rewritten to comprise operations directed only to the at least one database table, wherein the resulting rewritten query is processed efficiently due to;

i) the elimination of the unnecessary columns;

ii) the elimination of unnecessary or redundant sorts;

iii) an effective processing of the ordered view, comprising the at least one sorting clause, without materialization; and

iv) fewer rows of data returned when the rewritten query is executed.

9. The computer readable storage media of claim 8, wherein the computer readable program code is further configured to:

execute the rewritten query.

10. The computer readable storage media of claim 8, wherein the computer readable program code configured to identify any sorts in the view definition that are unnecessary or redundant in the query is further configured to:

process the query predicates;

determine that the view definition comprises one or more view sorts;

determine whether the view sort is used in the query or affects query results; and

in response to determining that the view sort is not used in the query and does not affect the query results, not apply the view sort to the query.

11. The computer readable storage media of claim 8, wherein the computer readable program code configured to identify any sorts in the view definition that are unnecessary or redundant in the query are further configured to:

process the query predicates;

determine that the view definition comprises one or more view sorts;

determine whether the view sort is used in the query or affects query results;

in response to determining that the view sort is used in the query or does affect the query results, determine whether the query comprises one or more sorts; and

in response to determining that the query does not comprise any sorts, apply the view sort to the query.

12. The computer readable storage media of claim 8, wherein the computer readable program code configured to identify any sorts in the view definition that are unnecessary or redundant in the query are further configured to:

process the query predicates;

determine that the view definition comprises one or more view sorts;

determine whether the view sort is used in the query or affects query results;

in response to determining that the view sort is used in the query or does affect the query results, determine whether the query comprises one or more query sorts;

in response to determining that the query comprises one or more query sorts, determine whether the view sort matches the query sort; and

in response to determining that the view sort matches the query sort, not apply the view sort to the query.

13. The computer readable storage media of claim 12, wherein the computer readable program code configured to identify any sorts in the view definition that are unnecessary or redundant in the query further are further configured to:

in response to determining that the view sort does not match the query sort, not apply the view sort to the query.

14. The computer readable storage media of claim 12, wherein the computer readable program code configured to identify any sorts in the view definition that are unnecessary or redundant in the query further are further configured to:

in response to determining that the view sort does not match the query sort, build a composite sort from the view sort and the query sort; and

apply the composite sort to the query.

15. A system, comprising:

a processor; and

a computer readable storage media having computer readable program code embodied therewith executable by the processor, the computer readable program code configured to;

process a query for database data in a database system that does not support view definitions containing a sorting clause, the query processed against an ordered view, without materialization of the ordered view, wherein the ordered view comprises operations directed to at least one database table, wherein a view definition that defines the ordered view comprises at least one sorting clause, wherein the view definition comprising the at least one sorting clause is not supported by the database system by;

obtaining the view definition for the ordered view;

obtaining the query to be executed on the database data, wherein the query comprises operations directed to the ordered view;

identifying any columns in the view definition that are unnecessary for the query;

after processing any predicates of the query, identifying any sorts in the view definition that are unnecessary or redundant in the query, wherein the sorts in the view definition are defined by the at least one sorting clause, and are not supported by the database system; and

rewriting the query to eliminate the unnecessary columns, and unnecessary or redundant sorts, wherein the query is rewritten to comprise operations directed only to the at least one database table, wherein the resulting rewritten query is processed efficiently due to;

i) the elimination of the unnecessary columns;

ii) the elimination of unnecessary or redundant sorts;

iii) an effective processing of the ordered view, comprising the at least one sorting clause, without materialization; and

iv) fewer rows of data returned when the rewritten query is executed.

16. The system of claim 15, wherein the computer readable program code is further configured to:

execute the rewritten query.

17. The system of claim 15, wherein the computer readable program code configured to identify any sorts in the view definition that are unnecessary or redundant in the query is further configured to:

process the query predicates;

determine that the view definition comprises one or more view sorts;

determine whether the view sort is used in the query or affects query results; and

in response to determining that the view sort is not used in the query and does not affect the query results, not apply the view sort to the query.

18. The system of claim 15, wherein the computer readable program code configured to identify any sorts in the view definition that are unnecessary or redundant in the query are further configured to:

process the query predicates;

determine that the view definition comprises one or more view sorts;

determine whether the view sort is used in the query or affects query results;

in response to determining that the view sort is used in the query or does affect the query results, determine whether the query comprises one or more sorts; and

in response to determining that the query does not comprise any sorts, apply the view sort to the query.

19. The system of claim 15, wherein the computer readable program code configured to identify any sorts in the view definition that are unnecessary or redundant in the query are further configured to:

process the query predicates;

determine that the view definition comprises one or more view sorts;

determine whether the view sort is used in the query or affects query results;

in response to determining that the view sort is used in the query or does affect the query results, determine whether the query comprises one or more query sorts;

in response to determining that the query comprises one or more query sorts, determine whether the view sort matches the query sort; and

in response to determining that the view sort matches the query sort, not apply the view sort to the query.

20. The system of claim 19, wherein the computer readable program code configured to identify any sorts in the view definition that are unnecessary or redundant in the query further are further configured to:

in response to determining that the view sort does not match the query sort, either not apply the view sort to the query or build a composite sort from the view sort and the query sort; and

apply the composite sort to the query when the composite sort is built.