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Re: Again, sorry, caching.

From: Neil Conway <nconway(at)klamath(dot)dyndns(dot)org>
To: Christopher Kings-Lynne <chriskl(at)familyhealth(dot)com(dot)au>
Cc: PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Again, sorry, caching.
Date: 2002-03-20 04:43:49
Message-ID: 1016599429.1196.10.camel@jiro (view raw, whole thread or download thread mbox)
Lists: pgsql-hackers
On Tue, 2002-03-19 at 21:40, Christopher Kings-Lynne wrote:
> 1. Implementing a byte-compatible query cache WILL improve the speed of
> repetitive queries over static data.

For some specific workloads, I think it has the potential to
significantly improve performance.

> 3. It is really hard to implement such a cache whilst keeping postgres
> maintainable and ACID compliant.

If we only consider implementations within Postgres itself, this is
probably true. However, I haven't seen anyone comment that there are
ACID-related concerns with the NOTIFY/LISTEN scheme that has been
suggested (and therefore, with the middle-tier caching daemon I

> 5. The main developers, or in fact the people with the ability to implement
> such a thing, either won't do it or can't be stuffed doing it...

I don't think it's a particularly good idea to implement the query cache
within the database itself. As for the middle-tier caching daemon I
suggested, I'm working on a design but I haven't begun implementation

> 3. We agree that such a query cache can be useful in some circumstances and
> could help postgres's performance in certain environments, but the will
> doesn't exist to implement it at the moment and it would also be difficult
> and messy.  Put it on the TODO list maybe.

I agree that a query cache implemented inside Postgres proper would be
messy and of dubious value, but I haven't heard of any show-stoppers WRT
my proposal (of course, if anyone knows of one, please speak up).


Neil Conway <neilconway(at)rogers(dot)com>

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