From: | david(at)lang(dot)hm |
---|---|
To: | Simon Riggs <simon(at)2ndquadrant(dot)com> |
Cc: | Csaba Nagy <nagy(at)ecircle-ag(dot)com>, Bill Moran <wmoran(at)collaborativefusion(dot)com>, pgsql-performance(at)postgresql(dot)org |
Subject: | Re: TB-sized databases |
Date: | 2007-11-28 21:55:23 |
Message-ID: | Pine.LNX.4.64.0711281352280.18750@asgard.lang.hm |
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Lists: | pgsql-performance |
On Wed, 28 Nov 2007, Simon Riggs wrote:
> On Wed, 2007-11-28 at 14:48 +0100, Csaba Nagy wrote:
>
>> In fact an even more useful option would be to ask the planner to throw
>> error if the expected cost exceeds a certain threshold...
>
> Well, I've suggested it before:
>
> statement_cost_limit on pgsql-hackers, 1 March 2006
>
> Would people like me to re-write and resubmit this patch for 8.4?
>
> Tom's previous concerns were along the lines of "How would know what to
> set it to?", given that the planner costs are mostly arbitrary numbers.
arbitrary numbers are fine if they are relativly consistant with each
other.
will a plan with a estimated cost of 1,000,000 take approximatly 100 times
as long as one with a cost of 10,000?
or more importantly, will a plan with an estimated cost of 2000 reliably
take longer then one with an estimated cost of 1000?
David Lang
> Any bright ideas, or is it we want it and we don't care about the
> possible difficulties?
>
>
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