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Serious Serious
Reported By: Vincent
Reported On: 5/8/2008
For: Version 4.26 Build 2
# 2612 Compound Query Expressions Not Being Rewritten by the Query Optimizer

I have been able to replicate a problem using the following SQL. I have 2 versions of dbsys. I am running both from the same folder using file-sharing pointing to the same data folder. One is version 4.25 b3 the other 4.26 b2. Version 4.25 b3 takes 1.5-2 seconds to run. Version 4.26 b2 takes 250-400 seconds to run. If I remove the JOINOPTIMIZECOSTS from the SQL, 4.26 b2 takes 1.5-2 seconds to run.

SELECT T1.PF1, T1.PF2, T1.RF1, T1.RF2
FROM Table1 AS T1 
LEFT OUTER JOIN Table2 AS T2 ON (T1.PF1=T2.PF1) AND (T1.PF2=T2.PF2) 
WHERE  (T1.PF1 = 'ANUMBER') AND  (upper(T1.RF1) LIKE  upper('ANAME%'))
ORDER BY T1.PF1, T1.RF1
JOINOPTIMIZECOSTS



Comments Comments
Query expressions that should have been rewritten in order to optimize the execution of the compound elements of the expression, were simply being left alone, resulting in much worse performance in some cases.


Resolution Resolution
Fixed Problem on 5/9/2008 in version 4.26 build 3


Products Affected Products Affected
DBISAM Additional Software and Utilities
DBISAM CLX Client-Server
DBISAM CLX Client-Server with Source
DBISAM CLX Standard
DBISAM CLX Standard with Source
DBISAM ODBC Client-Server
DBISAM ODBC Client-Server with Source
DBISAM ODBC Standard
DBISAM ODBC Standard with Source
DBISAM ODBC Trial
DBISAM VCL Client-Server
DBISAM VCL Client-Server with Source
DBISAM VCL Standard
DBISAM VCL Standard with Source
DBISAM VCL Trial

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