Re: Strange logic for partial index proving

From: Richard Huxton <dev(at)archonet(dot)com>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: laser <laser(at)toping(dot)com(dot)cn>, pgsql-hackers(at)postgresql(dot)org
Subject: Re: Strange logic for partial index proving
Date: 2005-06-23 14:51:17
Message-ID: 42BACC65.6010102@archonet.com
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Tom Lane wrote:
> Richard Huxton <dev(at)archonet(dot)com> writes:
>
>>laser wrote:
>>>Aggregate (cost=100009638.60..100009638.60 rows=1 width=0) (actual
>>>time=1567.317..1567.318 rows=1 loops=1)
>>>-> Seq Scan on partial_idx_t (cost=100000000.00..100008327.88
>>>rows=524288 width=0) (actual time=0.046..906.747 rows=524288 loops=1)
>>>Total runtime: 1567.401 ms
>
>
>>I'd say your configuration settings are a long way from accurate.
>
>
> Actually, I'd say these estimates are pretty good. Ignoring the
> 100000000 penalty from "set enable_seqscan off", we have:

<sigh> of course the 100 million is from seqscan=off, that's what he was
demonstrating. Sometimes I wonder why I get out of bed in the mornings :-/

--
Richard Huxton
Archonet Ltd

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