| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Simon Riggs <simon(at)2ndquadrant(dot)com> |
| Cc: | pgsql-hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: SeqScan costs |
| Date: | 2008-08-12 19:46:42 |
| Message-ID: | 23950.1218570402@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Simon Riggs <simon(at)2ndquadrant(dot)com> writes:
> Proposal: Make the first block of a seq scan cost random_page_cost, then
> after that every additional block costs seq_page_cost.
This is only going to matter for a table of 1 block (or at least very
few blocks), and for such a table it's highly likely that it's in RAM
anyway. So I'm unconvinced that the proposed change represents a
better model of reality.
Perhaps more to the point, you haven't provided any actual evidence
that this is a better approach. I'm disinclined to tinker with the
fundamental cost models on the basis of handwaving.
regards, tom lane
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