Re: index vs. seq scan choice?

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От George Pavlov
Тема Re: index vs. seq scan choice?
Дата
Msg-id 8C5B026B51B6854CBE88121DBF097A86DEA6D3@ehost010-33.exch010.intermedia.net
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Ответ на Re: index vs. seq scan choice?  (Tom Lane <tgl@sss.pgh.pa.us>)
Ответы Re: index vs. seq scan choice?  ("Joshua D. Drake" <jd@commandprompt.com>)
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> From: Tom Lane
> "George Pavlov" <gpavlov@mynewplace.com> writes:
> >> From: Joshua D. Drake [mailto:jd@commandprompt.com]
> >> In those rare cases wouldn't it make more sense to just set
> >> enable_seqscan to off; run query; set enable_seqscan to on;
>
> > 1. these cases are not that rare (to me);
>
> It strikes me that you probably need to adjust the planner cost
> parameters to reflect reality on your system.  Usually dropping
> random_page_cost is the way to bias the thing more in favor of
> index scans.

Thanks, Tom, I will try that. Seems better than fiddling with
enable_seqscan around every query/transaction.

Joshua, I fail to understand why setting and unsetting enable_seqscan on
a per query/transaction basis is in any way preferable to query hints?
Don't get me wrong, I don't like the idea of hints, and I have read the
archives on the subject and I agree with the philosophy, but if the
optimization toolkit for routine application queries is going to include
setting config parameters that just smacks of hints by another name...

George

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