REMOVING NODES FROM A QUERY TREE BASED ON A RESULT SET

• US 20070239673A1
• Filed: 04/05/2006
• Published: 10/11/2007
• Est. Priority Date: 04/05/2006
• Status: Abandoned Application

• Current Assignee: International Business Machines Corporation
• Original Assignee: International Business Machines Corporation
• Inventors: Santosuosso, John, Bestgen, Robert, Barsness, Eric
• Application Number:
  US11/278,714
• Publication Number:
  US 20070239673A1
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G06F 16/24542 Plan optimisation

Abstract

In an embodiment, a query tree is created that represents a query expression, where the query tree includes a union of nodes. Each of the nodes represents a respective partition of a table, and the query expression specifies a key value and the table. A determination is made whether a result set exists that includes the key value, where the result set was previously retrieved from the table. If the determination is true, a decision is made based on the result set whether the key value is stored in the respective partition represented by each of the nodes. The nodes for which the key value is not stored in the respective partition are removed from the query tree to create an optimization tree, and the optimization tree is used to retrieve data from the table. In this way, nodes that are not necessary to be searched may be removed from query trees, in order to increase the performance of the query.

Claims

1. A method comprising:

creating a query tree that represents a first query expression, wherein the query tree comprises a union of a plurality of nodes, wherein each of the nodes represents a respective partition of a table, and wherein the first query expression specifies a key value;

determining whether a result set exists that comprises the key value, wherein the result set was previously retrieved from the table; and

if the determining is true, deciding based on the result set whether the key value is stored in the respective partition represented by each of the plurality of nodes.

2. The method of claim 1 further comprising:

removing the nodes for which the key value is not stored in the respective partition from the query tree to create an optimization tree; and

retrieving data from the table via the optimization tree.

3. The method of claim 2, wherein the retrieving further comprises:

creating an execution plan based on the optimization tree.

4. The method of claim 3, wherein the retrieving further comprises:

searching the partitions represented by the nodes of the optimization tree for the key value via the execution plan.

5. The method of claim 1, wherein the deciding further comprises:

deciding whether the key value and a partition key value that represents the respective partition are both in a same row of the result set.

6. The method of claim 1, wherein the result set was previously retrieved in response to a second query expression, wherein the second query expression was processed prior to the first query expression.

7. The method of claim 1, further comprising:

if the determining is false, creating the result set.

8. The method of claim 1, further comprising:

if the determining is false, recommending that a user create the result set.

9. A signal-bearing medium encoded with instructions, wherein the instructions when executed comprise:

creating a query tree that represents a first query expression, wherein the query tree comprises a union of a plurality of nodes, wherein each of the nodes represents a respective partition of a table, and wherein the first query expression specifies a key value and the table;

determining whether a result set exists that comprises the key value, wherein the result set was previously retrieved from the table;

if the determining is true, deciding based on the result set whether the key value is stored in the respective partition represented by each of the plurality of nodes;

removing the nodes for which the key value is not stored in the respective partition from the query tree to create an optimization tree; and

retrieving data from the table via the optimization tree.

10. The signal-bearing medium of claim 9, wherein the retrieving further comprises:

creating an execution plan based on the optimization tree.

11. The signal-bearing medium of claim 10, wherein the retrieving further comprises:

searching the partitions represented by the nodes of the optimization tree for the corresponding key value via the execution plan.

12. The signal-bearing medium of claim 9, wherein the deciding further comprises:

deciding whether the key value and a partition key value that represents the respective partition are both in a same row of the result set.

13. The signal-bearing medium of claim 9, wherein the result set was previously retrieved in response to a second query expression, wherein the second query expression was processed prior to the first query expression.

14. The signal-bearing medium of claim 9, further comprising:

if the determining is false, creating the result set.

15. The signal-bearing medium of claim 9, further comprising:

if the determining is false, recommending that a user create the result set.

16. A method for configuring a computer, comprising:

configuring the computer to create a query tree that represents a first query expression, wherein the query tree comprises a union of a plurality of nodes, wherein each of the nodes represents a respective partition of a table, and wherein the first query expression specifies a key value and the table;

configuring the computer to determine whether a result set exists that comprises the key value, wherein the result set was previously retrieved from the table;

configuring the computer to, if the determining is true, decide based on the result set whether the key value is stored in the respective partition represented by each of the plurality of nodes;

configuring the computer to remove the nodes for which the key value is not stored in the respective partition from the query tree to create an optimization tree; and

configuring the computer to retrieve data from the table via the optimization tree.

17. The method of claim 16, wherein the configuring the computer to retrieve further comprises:

configuring the computer to create an execution plan based on the optimization tree.

18. The method of claim 17, wherein the configuring the computer to retrieve further comprises:

configuring the computer to search the partitions represented by the nodes of the optimization tree for the key value via the execution plan.

19. The method of claim 16, wherein the configuring the computer to decide further comprises:

configuring the computer to decide whether the key value and a partition key value that represents the respective partition are both in a same row of the result set.

20. The method of claim 16, wherein the result set was previously retrieved in response to a second query expression, wherein the second query expression was processed prior to the first query expression.