Oracle-L: RE: Optimizer choosing different index

From: <Long.Nguyen_at_csiro.au>
Date: Wed, 22 May 2002 16:28:18 -0800
Message-ID: <F001.004688CB.20020522162818@fatcity.com>

I guess Oracle determines the execution plan based on many factors, and one of them would be the data size and distribution. If you have different data size in prod and dev then the execution plan may be different.

Long

-----Original Message-----
Sent: Thursday, 23 May 2002 6:04 AM
To: Multiple recipients of list ORACLE-L

Oracle 8.0.5, peoplesoft version 7.51

We have a report that has stopped working due to running out of temporary space.

The first step was to check the explain plan. I compared the explain plans between the
production database and a dev database that is approx 6 months old. They were very different.

Upon review we found that the production database is now using a different index then the dev system.

I made a copy of the prod database, deleted the index, and the explain plan and sql performed the
same as the dev system.

Question I have is, what would cause the cost based optimizer to choose a different index. The only thing
that has changed is the number of rows in the source table.

Statistics are up-todate, and I have re-built the indexes in question.

Thanks

Darren

Darren Browett P.Eng This message
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