I added an index to a table in order to speed up a query in my
application.
The query, after the index creation, improved its performances but
another
query (a join on several tables one of which was the table on which I
added the index)
increased its execution time from four seconds to more than an hour (I
actually killed
the process after one hour).
How is it possible? Why the optimizer doesn't simply ignore the new
index if it is not
useful for him?
Moreover I added another index on the columns that were present in the
where condition
of the second query but until I dropped the first index the second query
didn't work.
Can anybody help me?
Giancarlo Sanna
IBM Italia S.p.A.
email: Giancarlo_Sanna_at_it.ibm.com
Received on Wed Jun 17 1998 - 10:15:52 CDT
