Re: How to keep a table in memory?

Added to TODO:

>
> * Consider allowing higher priority queries to have referenced buffer
>   cache pages stay in memory longer
>
>   http://archives.postgresql.org/pgsql-hackers/2007-11/msg00562.php

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Tom Lane wrote:
> Devrim GÜNDÜZ <devrim@CommandPrompt.com> writes:
> > So, IMHO, saying "trust your OS + PostgreSQL" is not a 100% perfect
> > approach for the people who are asking to keep their objects on RAM,
> > even though I know that there is nothing we can say right now.
> 
> Well, nothing is a 100% solution.  But my opinion is that people who
> think they are smarter than an LRU caching algorithm are typically
> mistaken.  If the table is all that heavily used, it will stay in memory
> just fine.  If it's not sufficiently heavily used to stay in memory
> according to an LRU algorithm, maybe the memory space really should be
> spent on something else.
> 
> Now there are certainly cases where a standard caching algorithm falls
> down --- the main one I can think of offhand is where you would like to
> give one class of queries higher priority than another, and so memory
> space should preferentially go to tables that are needed by the first
> class.  But if that's your problem, "pin these tables in memory" is
> still an awfully crude solution to the problem.  I'd be inclined to
> think instead about a scheme that lets references made by
> higher-priority queries bump buffers' use-counts by more than 1,
> or some other way of making the priority considerations visible to an
> automatic cache management algorithm.
> 
>             regards, tom lane
> 
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