RE: Adding SQL indes causing performance degradation?

["McCallion, Martin" <martin.mccallion@xxxxxxxxx>]

> Does anyone have experience with existing applications 
> slowing down after
> adding 1 or more SQL indexes to a physical file used by the 
> application?

We had a client report a problem like this a while back.  I don't quite
know all the details, unfortunately.

Initially they thought it was to do with our application (which is
written in Java and was accessing the database using JDBC, which may or
may not be relevant).  The application was configured to do a lookup to
one of their tables for every transaction it processed.  They had added
an index to the table in question, I think in an attempt to improve
performance.  The performance got worse, however.

After some investigation they determined (IIRC) that the key of the new
index was of a different data type from the field on the underlying file
-- I think it might have been an integer key over a packed field.  The
increased run time appeared to come from the database having to convert
the data for every record.

HTH

Cheers,

Martin.

--
Martin McCallion
Senior Technical Consultant
Misys Wholesale Banking Systems
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