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MF63321 - OSP-PERFM INDEX NOT USED DUE TO INCORRECT 'IS NOT NULL' EKR

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Abstract

OSP-PERFM INDEX NOT USED DUE TO INCORRECT 'IS NOT NULL' EKR


Pre/Co-Requisite PTF / Fix List

REQ  LICENSED      PTF/FIX  LEVEL

TYPE PROGRAM  REL  NUMBER   MIN/MAX  OPTION
---- -------- ---  -------  -------  ------
CO   5770999  710  MF62374   00/00    0000
CO   5770999  710  MF52433   00/00    0000



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APAR Error Description / Circumvention

-----------------------------------------------
EKR was giving an estimate of 100% for the IsNotNull when
actually all rows are Null for a particular column. This invalid
estimate caused the desirable index to not be used.

CORRECTION FOR APAR MA46186 :
-----------------------------
The algorithm for calculating the number of non-NULL values for
a given key was found to have a bug that resulted in an estimate
of 100% when it should have been 0%.  The estimate problem is
specific to EKRs that are trying to determine the non-NULL
count.

CIRCUMVENTION FOR APAR MA46186 :
--------------------------------
None.


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Special Instructions


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THIS PTF CAN BE APPLIED IMMEDIATE OR DELAYED.



Supersedes

PTF/FIX NO(S).  APAR TITLE LINE
--------------  ------------------------------------------------------------
   MF62377      LIC-DB-OTHER Internal Database Maintenance.
   MF61487      LIC-DB-OTHER Internal database maintenance
   MF60663      LIC-DB Internal maintenance
   MF60584      LIC-DB Internal maintenance
   MF57329      LIC-DB-OTHER-LOOP Job loops in DbEstimateKeyRange
   MF56979      LIC-DB-PERFM Long running key range estimates are being aged
   MF56882      LIC-DB-PERFM Extend size of key range estimate cache to avoi
   MF52432      LIC-DB-OTHER-PERFM HIGH MACHINE GATING ON INDEX.
   MF51884      LIC-DB-PERFM Need EVI stat to detect skewed values on a tabl
   MF51429      LIC-DB-PERFM AN TABLE SCAN IS BEING CHOSEN OVER A INDEX.
   MF51276      LIC-DB-PERFM Non-preload brings not targeting specific pool
   MF49890      LIC-DB Component dbix failed to compile during build
   MF49604      LIC-DB Expose New DataSpace / Index Attribute
   MF48385      LIC-DB-OTHER-F/#DBXBINX-T/QDMCOPEN-MSGMCH3203

Summary Information

System..............................i
Models..............................
Release.............................V7R1M0
Licensed Program...............5770999
APAR Fixed..........................View details for APAR MA46186
Superseded by:......................
Recompile...........................N
Library.............................QSYS
MRI Feature ........................NONE
Cum Level...........................NONE


System i Support

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Document Information

Modified date:
26 July 2017