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Problem IT19506
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Status: Closed |
The optimizer might choose a non-optimal full table scan compared to a better performing index access on the inner of an NLJOIN |
| product: |
DB2 FOR LUW / DB2FORLUW / A50 - DB2 |
| Problem description: |
In some cases, the optimizer might over-estimate the cost of an
NLJOIN operation, leading to the optimizer favoring a full table
scan of a table access over an index access scan of that access
on the inner of a NLJOIN. Typically, the favored choice will be
a sub-optimal HSJOIN with the table access on the outer branch. |
| Problem Summary: |
****************************************************************
* USERS AFFECTED: *
* ALL *
****************************************************************
* PROBLEM DESCRIPTION: *
* See Error Description *
****************************************************************
* RECOMMENDATION: *
* Upgrade to Db2 10.5 Fix Pack 9 or higher *
**************************************************************** |
| Local Fix: |
Ensuring that the statistics are up to date can help alleviate
this problem. If not, an optimization guideline can be used to
request the NLJOIN method. |
| Solution |
First fixed in Db2 10.5 Fix Pack 9 |
| Workaround |
not known / see Local fix |
| Timestamps |
Date - problem reported :
Date - problem closed :
Date - last modified :
| 02.03.2017
29.09.2017
29.09.2017 |
| Problem solved at the following versions (IBM BugInfos) |
9.0.
|
| Problem solved according to the fixlist(s) of the following version(s) |
