Rajesh Kumar Mallah <[EMAIL PROTECTED]> writes:
> NOT EXISTS is taking almost double time than NOT IN .
> I know IN has been optimised in 7.4 but is anything 
> wrong with the NOT EXISTS?

That's the expected behavior in 7.4.  EXISTS in the style you are using
it effectively forces a nestloop-with-inner-indexscan implementation.
As of 7.4, IN can do that, but it can do several other things too,
including the hash-type plan you have here.  So assuming that the
planner chooses the right plan choice (not always a given ;-))
IN should be as fast or faster than EXISTS in all cases.

                        regards, tom lane

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