"vinita bansal" <[EMAIL PROTECTED]> writes:
> Also, a particular query which was taking a min or less with postgres 7 is 
> taking 15 mins now.
> Here is the query plan for the query both for postgres 7.4.6 and postgres 8:

It's hard to say anything about this when you only provided EXPLAIN and
not EXPLAIN ANALYZE results.  The rowcount estimates are obviously a lot
different between 7.4 and 8.0, but are they more accurate or less so?
Can't tell from EXPLAIN.

> Why is this happening.

Have you vacuumed and/or analyzed all of the tables used in the query?
It looks like a statistical estimation problem to me.  People frequently
complain that a new version has horrible performance because they forgot
to analyze their database after migrating ...

                        regards, tom lane

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