Database system index selection using candidate index selection for a workload

• US 5,960,423 A
• Filed: 12/01/1997
• Issued: 09/28/1999
• Est. Priority Date: 08/15/1997
• Status: Expired due to Term

• Current Assignee: Microsoft Technology Licensing LLC (Microsoft Corporation)
• Original Assignee: Microsoft Corporation
• Inventors: Chaudhuri, Surajit, Narasayya, Vivek
• Primary Examiner(s): Black, Thomas G.
• Assistant Examiner(s): Mizrahi, Diane D.
• Application Number:
  US08/980,830
• Time in Patent Office: 666 Days
• Field of Search: 707/1, 707/2, 707/3, 707/5, 707/101, 707/205, 702/186, 340/825.35, 348/286, 385/102, 156/256
• US Class Current: 707/715
• CPC Class Codes: G06F 16/22 Indexing; Data structures therefor; Storage structures
• CPC Class Codes: Y10S 707/99931 Database or file accessing
• CPC Class Codes: Y10S 707/99932 Access augmentation or optimizing
• CPC Class Codes: Y10S 707/99933 Query processing, i.e. searching
• CPC Class Codes: Y10S 707/99935 Query augmenting and refining, e.g. inexact access
• CPC Class Codes: Y10S 707/99942 Manipulating data structure, e.g. compression, compaction, compilation
• CPC Class Codes: Y10S 707/99953 Recoverability

Abstract

An index selection tool helps reduce costs in time and memory in selecting an index configuration or set of indexes for use by a database server in accessing a database in accordance with a workload of queries. The index selection tool attempts to reduce the number of indexes to be considered, the number of index configurations to be enumerated, and the number of invocations of a query optimizer in selecting an index configuration for the workload.

Claims

1. A method for determining a set of candidate indexes for a workload of queries to be executed against a database, the method comprising the steps of:

(a) selecting an index configuration of one or more indexes for each query of the workload such that the selected index configuration helps optimize execution of the query against the database; and

(b) determining the set of candidate indexes for the workload as comprising indexes from each index configuration selected for the selecting step (a).

2. The method of claim 1, wherein the index configuration selected for each query for the selecting step (a) comprises at most a predetermined number of indexes.

3. The method of claim 1, wherein the selecting step (a) comprises the step of selecting for a given query of the workload an index configuration determined to have a least estimated cost for executing the given query against the database.

4. The method of claim 1, wherein the selecting step (a) selects for each query of the workload one or more index configurations that help optimize execution of the query against the database.

5. The method of claim 4, wherein the selecting step (a) selects for a given query of the workload an index configuration determined to have a least estimated cost for executing the given query against the database and any other index configurations determined to have for the given query an estimated cost within a predetermined percent of the least estimated cost.

6. The method of claim 5, wherein the predetermined percent is approximately ten percent.

7. The method of claim 1, comprising the step of:

(c) selecting an index configuration comprising at least one of the candidate indexes for use by a database server to execute queries of the workload against the database.

8. The method of claim 7, wherein the selecting step (a) is performed by an index configuration enumeration tool, and

wherein the selecting step (c) is also performed by the index configuration enumeration tool.

9. A computer readable medium having computer-executable instructions for performing the steps of claim 1.

10. A computer readable medium having computer-executable instructions for performing the steps of claim 4.

11. A computer readable medium having computer-executable instructions for performing the steps of claim 7.

12. A computer readable medium having computer-executable instructions for performing the steps of claim 8.

13. A method for determining a set of candidate indexes for a workload of queries to be executed against a database, the method comprising the steps of:

(a) determining a respective set of one or more indexes for each query of the workload;

(b) determining estimated costs to execute each query of the workload against the database for index configurations comprising one or more indexes from the respective set of one or more indexes for the query;

(c) selecting one of the index configurations for each query of the workload based on the estimated costs determined for the determining step (b); and

(d) determining the set of candidate indexes for the workload as comprising indexes from each index configuration selected for the selecting step (c).

14. The method of claim 13, wherein the determining step (a) comprises the step of determining a respective set of one or more indexable columns for each query.

15. The method of claim 13, wherein the determining step (b) comprises the step of determining estimated costs to execute each query of the workload against the database for index configurations comprising at most a predetermined number of indexes from the respective set of one or more indexes for the query.

16. The method of claim 13, wherein the selecting step (c) comprises the step of selecting for each query of the workload the index configuration having the least estimated cost for the query.

17. The method of claim 13, wherein the selecting step (c) selects one or more index configurations for each query of the workload based on the estimated costs determined for the determining step (b).

18. The method of claim 17, wherein the selecting step (c) selects for a given query of the workload an index configuration determined to have a least estimated cost for the given query and any other index configurations determined to have for the given query an estimated cost within a predetermined percent of the least estimated cost.

19. The method of claim 18, wherein the predetermined percent is approximately ten percent.

20. The method of claim 13, wherein the determining step (b) comprises the steps of:

(i) determining one or more atomic index configurations for a given query of the workload,

(ii) determining an estimated cost to execute the given query against the database for each determined atomic index configuration using a query optimizer of a database server that is to execute the given query against the database, and

(iii) determining an estimated cost to execute the given query against the database for an index configuration comprising one or more indexes from the respective set of one or more indexes for the given query based on the estimated cost for each determined atomic index configuration as determined for the determining step (b)(ii).

21. The method of claim 13, comprising the steps of:

(e) determining estimated costs to execute each query of the workload against the database for index configurations comprising at least one of the candidate indexes; and

(f) selecting, based on the estimated costs determined for the determining step (e), one of the index configurations comprising at least one of the candidate indexes for use by a database server to execute queries of the workload against the database.

22. The method of claim 21, wherein the determining step (b) and the selecting step (c) are performed by an index configuration enumeration tool, and

wherein the determining step (e) and the selecting step (f) are also performed by the index configuration enumeration tool.

23. A computer readable medium having computer-executable instructions for performing the steps of claim 13.

24. A computer readable medium having computer-executable instructions for performing the steps of claim 17.

25. A computer readable medium having computer-executable instructions for performing the steps of claim 21.

26. A computer readable medium having computer-executable instructions for performing the steps of claim 22.