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Problem IT35798
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Status: Closed |
SLOW PERFORMANCE IN DPF OR CDE WHEN RUNNING A QUERY WITH SCALAR SUBQUERIES AND AN OUTER JOIN
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| product: |
DB2 FOR LUW / DB2FORLUW / B50 - DB2 |
| Problem description: |
A query with the following characteristic could run slow in MPP
environment;
* A query has more than one scalar subqueries which include a
correlated predicate
* A query has at least one outer join.
* There's a correlation in one of scalar subqueries which
source is from the row-preserving side of the outer join.
* There's another correlation in one of scalar subqueries which
source is not from the row-preserving side of the outer join.
During the rewrite, the scalar subquery with the correlation not
coming from the outer join is wrongfully pushed down under the
outer join. This could form another correlation deep in the plan
which could be the reason of the slowness.
### Workaround
/*
*/ |
| Problem Summary: |
****************************************************************
* USERS AFFECTED: *
* CDE *
****************************************************************
* PROBLEM DESCRIPTION: *
* See Error Description *
****************************************************************
* RECOMMENDATION: *
* /* *
* *
* *
* *
* */ *
**************************************************************** |
| Local Fix: |
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| Solution |
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| Workaround |
****************************************************************
* USERS AFFECTED: *
* CDE *
****************************************************************
* PROBLEM DESCRIPTION: *
* See Error Description *
****************************************************************
* RECOMMENDATION: *
* /* *
* *
* *
* *
* */ *
**************************************************************** |
| Timestamps |
Date - problem reported :
Date - problem closed :
Date - last modified :
| 04.02.2021
25.03.2021
06.04.2021 |
| Problem solved at the following versions (IBM BugInfos) |
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| Problem solved according to the fixlist(s) of the following version(s) |
