Hash join not being used

We have a query that is a good candidate for a hash-join operation. As a matter of fact, when we force it to use a hash-type join (with a hint), the
elapsed time of the query goes from 90 minutes to about 2 minutes.

However, we are unable to force it to use a hash-join, without using the hint.

What perplexes us is that a month ago, the query was using a hash-join on its
own, without our intervention.

Any clues as to why the optimizer would change its mind and stop using a hash-join? Received on Mon Jun 26 2000 - 08:05:23 CDT