|
Problem IC63863
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Status: Closed |
OPTIMIZER USES FIRST TUPLE COST ONLY TO SELECT ACCESS PLAN |
| product: |
DB2 FOR LUW / DB2FORLUW / 970 - DB2 |
| Problem description: |
In a table with a large number of empty pages at the front of
the file, and a 0 cardinality, the optimizer uses First Tuple
Cost to select a plan. What the optimizer does not take into
account, when computing the First Tuple Cost, is that when the
table is empty, it will need to read the entire table to
discover it. Not just the first page of the table. There is a
similar issue with Index Scans - in that only the root page of
the index needs to be read to discover it is empty. The
optimizer does not currently fully, and properly deal with empty
indexes either. |
| Problem Summary: |
|
| Local Fix: |
Running Reorg on a regular basis. |
| available fix packs: |
DB2 Version 9.7 Fix Pack 1 for Linux, UNIX, and Windows
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 7 for Linux, UNIX, and Windows
DB2 Version 9.7 Fix Pack 9a for Linux, UNIX, and Windows
DB2 Version 9.7 Fix Pack 6 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
|
| Solution |
First fixed in FP5 |
| Workaround |
not known / see Local fix |
| Timestamps |
Date - problem reported :
Date - problem closed :
Date - last modified :
| 21.10.2009
17.02.2010
17.02.2010 |
| Problem solved at the following versions (IBM BugInfos) |
|
| Problem solved according to the fixlist(s) of the following version(s) |
| 9.7.0.1
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