From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
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To: | Willem Buitendyk <willem(at)pcfish(dot)ca> |
Cc: | pgsql-general(at)postgresql(dot)org |
Subject: | Re: Mechanics of Select |
Date: | 2008-02-10 23:45:09 |
Message-ID: | 11648.1202687109@sss.pgh.pa.us |
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Lists: | pgsql-general |
Willem Buitendyk <willem(at)pcfish(dot)ca> writes:
> I have the following function that returns the first day of the next
> month from whatever date is inserted. If I use this as part of a select
> statement then it takes almost twice as long to perform. Is this
> because for each scanned record this function is being called? If so
> any ideas how I could make this only occur once?
Don't declare it VOLATILE, when (AFAICS) you have no reason to.
It would be evaluated only once if it were marked IMMUTABLE.
BTW, I think you're doing it the hard way --- this could almost
certainly be a one-liner if you were using the available date
arithmetic facilities.
regards, tom lane
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