|
Problem IT37607
|
Status: Closed |
OPTIMIZE FOR N ROWS CLAUSE CAUSES THE QUERY TO SCAN THE SUB-OPTIMAL PLAN
|
| product: |
DB2 FOR LUW / DB2FORLUW / B50 - DB2 |
| Problem description: |
When both FFNR and OFNR is specified , optimizer can pick a
sub-optimial plan
with a few exceptions, optimizer automatically optimize for N
rows, if fetch first N rows is specified. So "optimize for N
row" clause is not necessary, and it exposes the costing bug.
The few exceptions are: when the select clause contains
distinct, OLAP functions, or aggregate functions (group by) |
| Problem Summary: |
****************************************************************
* USERS AFFECTED: *
* ALL *
****************************************************************
* PROBLEM DESCRIPTION: *
* See Error Description *
****************************************************************
* RECOMMENDATION: *
* There is no resolution. The issue is a limitation of the *
* product, introduced in v95. *
**************************************************************** |
| Local Fix: |
1)remove the "optimize for N row" clause. Since v95,
(2) or Suggest to add an index |
| Solution |
|
| Workaround |
****************************************************************
* USERS AFFECTED: *
* ALL *
****************************************************************
* PROBLEM DESCRIPTION: *
* See Error Description *
****************************************************************
* RECOMMENDATION: *
* There is no resolution. The issue is a limitation of the *
* product, introduced in v95. *
**************************************************************** |
| Timestamps |
Date - problem reported :
Date - problem closed :
Date - last modified :
| 13.07.2021
17.05.2022
17.05.2022 |
| Problem solved at the following versions (IBM BugInfos) |
|
| Problem solved according to the fixlist(s) of the following version(s) |
