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Problem IC65989
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Status: Closed |
QUERY PERFORMANCE PROBLEM WITH A JOIN PREDICATE THAT INVOLVES A CASE STATEMENT THAT RETURNS A MIX OF CONSTANT AND COLUMN VALUES |
| product: |
DB2 FOR LUW / DB2FORLUW / 970 - DB2 |
| Problem description: |
The CASE statement used to generate a value that was applied as
a start/stop key in an index access, but due to the rewrite of
the CASE-based predicate to a series of "AND" and "OR"
pedicates, the rewritten predicate is applied as a SARG
predicate on an IXSCAN or TBSCAN |
| Problem Summary: |
The CASE statement used to generate a value that was applied as
a start/stop key in an index access, but due to the rewrite of
the CASE-based predicate to a series of "AND" and "OR"
pedicates, the rewritten predicate is applied as a SARG
predicate on an IXSCAN or TBSCAN |
| Local Fix: |
workaround is to replace one of the simple column expressions or
constants in the 'THEN' portion of the WHEN clause with a more
complex expression, or if the CASE does not return a NULL, wrap
the CASE in a coalesce function (i.e. join_col = coalesce( CASE
... END, 1)) |
| available fix packs: |
DB2 Version 9.7 Fix Pack 2 for Linux, UNIX, and Windows
DB2 Version 9.7 Fix Pack 3 for Linux, UNIX, and Windows
DB2 Version 9.7 Fix Pack 3a for Linux, UNIX, and Windows
DB2 Version 9.7 Fix Pack 4 for Linux, UNIX, and Windows
DB2 Version 9.7 Fix Pack 5 for Linux, UNIX, and Windows
DB2 Version 9.7 Fix Pack 6 for Linux, UNIX, and Windows
DB2 Version 9.7 Fix Pack 7 for Linux, UNIX, and Windows
DB2 Version 9.7 Fix Pack 9a for Linux, UNIX, and Windows
DB2 Version 9.7 Fix Pack 8 for Linux, UNIX, and Windows
DB2 Version 9.7 Fix Pack 9 for Linux, UNIX, and Windows
DB2 Version 9.7 Fix Pack 10 for Linux, UNIX, and Windows
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| Solution |
workaround is to replace one of the simple column expressions or
constants in the 'THEN' portion of the WHEN clause with a more
complex expression, or if the CASE does not return a NULL, wrap
the CASE in a coalesce function (i.e. join_col = coalesce( CASE
... END, 1)) |
| Workaround |
workaround is to replace one of the simple column expressions or
constants in the 'THEN' portion of the WHEN clause with a more
complex expression, or if the CASE does not return a NULL, wrap
the CASE in a coalesce function (i.e. join_col = coalesce( CASE
... END, 1)) |
| Timestamps |
Date - problem reported :
Date - problem closed :
Date - last modified :
| 02.02.2010
13.05.2010
13.05.2010 |
| Problem solved at the following versions (IBM BugInfos) |
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| Problem solved according to the fixlist(s) of the following version(s) |
| 9.7.0.2
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