Re: Wrong plan for simple join with index on FK

From: "Zeugswetter Andreas DCP SD" <ZeugswetterA(at)spardat(dot)at>
To: "Pavel Stehule" <pavel(dot)stehule(at)hotmail(dot)com>, <kleptog(at)svana(dot)org>
Cc: <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Wrong plan for simple join with index on FK
Date: 2006-05-16 12:35:43
Message-ID: E1539E0ED7043848906A8FF995BDA579010543B4@m0143.s-mxs.net
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> >These are all minor abberations though, on the whole the estimates
are
> >pretty good. Perhaps you need to tweak the values of random_page_cost
> >and similar variables.
>
> Thank You, It's general problem or only mine? I have "100%"
> standard current PC.

The default random_page_cost assumes some concurrent activity. If your
PC does nothing else concurrently, the performance of a seq scan will
be underestimated.

Try to do the statement with some concurrent disk load and you will most
likely
see that the 1. plan is faster. (assuming the tables are not fully
cached)

Andreas

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