Re: Tablespaces

From: "Zeugswetter Andreas SB SD" <ZeugswetterA(at)spardat(dot)at>
To: "Greg Stark" <gsstark(at)mit(dot)edu>, <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Tablespaces
Date: 2004-06-11 10:02:40
Message-ID: 46C15C39FEB2C44BA555E356FBCD6FA40184D0FB@m0114.s-mxs.net
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> > With the rule system and two underlying tables one could make it work by
> > hand I think.
>
> The rule system could be used to do this, but there was some discussion of
> using inherited tables to handle it. However neither handles the really hard
> part of detecting queries that use only a part of the table and taking that
> into account in generating the plan.

I think the consensus should be to add smarts to the planner to include
static constraint information to reduce table access.

e.g if you have a constraint "acol integer, check acol < 5"
and you have a query with a "where acol = 10" you could reduce that
to "where false". This would help in all sorts of situations not only
partitioned/inherited tables. I am not sure what the runtime cost of
such an inclusion would be, so maybe it needs smarts to only try in certain
cases ?

Andreas

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