Re: Function result cacheing

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Philip Warner <pjw(at)rhyme(dot)com(dot)au>
Cc: pgsql-hackers(at)postgresql(dot)org
Subject: Re: Function result cacheing
Date: 2002-08-17 04:18:28
Message-ID: 29521.1029557908@sss.pgh.pa.us
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Philip Warner <pjw(at)rhyme(dot)com(dot)au> writes:
> Obviously this is not a 7.3 item, but would people support such
> functionality going into a future version?

Actually, I wouldn't. I can think of very few situations where
such caching is useful, and I don't believe that the mechanism required
would pay for itself. In the cases where a cache does make sense,
it's sufficiently application-specific that a generic "cache on a key
consisting of the function arguments" isn't the right thing anyway;
you'll find you want some internal logic to decide what to cache and
what key to use to retrieve it. Furthermore, a generic cache will have
no clue whatever about cache-invalidating events, thus further
restricting its usefulness. (Your suggestion of "flush at transaction
end" is too short-term for most applications, too long-term for some,
and just right for hardly any.)

Build the cache internally to your function if you need it.

regards, tom lane

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