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Re: query cache

From: Greg Stark <stark(at)mit(dot)edu>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Billy Earney <billy(dot)earney(at)gmail(dot)com>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: query cache
Date: 2012-03-23 16:29:28
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Lists: pgsql-hackers
On Fri, Mar 23, 2012 at 3:49 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> The complication, opportunities for bugs, and general slowdown
> associated with that would outweigh any possible gain, in the opinion
> of most hackers who have thought about this.

I wouldn't be quite so pessimistic. I think the problem is that the
hard part in doing this for real is all the parts the proposal glosses
over. How much memory is it worth dedicating to the cache before the
cost of that memory costs more than it helps? How do you invalidate
cache entries efficiently enough that it doesn't become a bottleneck?

Also, you need to identify the specific advantages you hope a built-in
cache would have over one implemented in the ORM or database library.
If there aren't any advantages then those solutions are much simpler.
And they have other advantages as well -- one of the main reason
people implement caches is so they can move the load away from the
bottleneck of the database to the more easily scaled out application.


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