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Re: COUNT & Pagination

From: Neil Conway <neilc(at)samurai(dot)com>
To: "scott(dot)marlowe" <scott(dot)marlowe(at)ihs(dot)com>
Cc: Rajesh Kumar Mallah <mallah(at)trade-india(dot)com>,David Shadovitz <david(at)www(dot)shadovitz(dot)com>,"pgsql-performance(at)postgresql(dot)org" <pgsql-performance(at)postgresql(dot)org>
Subject: Re: COUNT & Pagination
Date: 2004-01-19 23:58:44
Message-ID: 8765f7ij7v.fsf@mailbox.samurai.com (view raw or flat)
Thread:
Lists: pgsql-performance
"scott.marlowe" <scott(dot)marlowe(at)ihs(dot)com> writes:
> Yes, previously run query should be faster, if it fits in kernel
> cache.

Or the PostgreSQL buffer cache.

> Plus, the design of Postgresql is such that it would have to do a
> LOT of cache checking to see if there were any updates to the
> underlying data between selects.

Last I checked (which was a while ago, admittedly), the MySQL design
completely purges the query cache for a relation whenever that
relation is mentioned in an INSERT, UPDATE, or DELETE. When this was
discussed (check the -hackers archives for more), IIRC the consensus
was that it's not worth implementing it if we can't do better than
that.

-Neil


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