From: Josh Close <narshe@gmail.com>
To: POSTGRES-PERFORMANCE <pgsql-performance@postgresql.org>
Subject: Re: slow queries, possibly disk io
Date: Fri, 27 May 2005 09:54:52 -0500
Message-ID: <4a0cafe205052707541373ab8a@mail.gmail.com> (raw)
In-Reply-To: <14584.1117204158@sss.pgh.pa.us>
References: <4a0cafe205052613242e0d4d10@mail.gmail.com>
<758d5e7f05052614232f6c9164@mail.gmail.com>
<4a0cafe205052706043ef8f53f@mail.gmail.com>
<4a0cafe205052706042d4e60e5@mail.gmail.com>
<14584.1117204158@sss.pgh.pa.us>
> I think you really want that seqscan to be an indexscan, instead.
> I'm betting this is PG 7.4.something? If so, probably the only
> way to make it happen is to simplify the now() expression to a constant:
>
> SELECT COALESCE( SUM( iNumSent ), 0 ) AS iNumSent
> FROM adaption.tblBatchHistory_\' || this_rServerIds.iId || \'
> WHERE tStamp > \\\'' || (now() - interval \'5 mins\')::text ||
> \'\\\'\';
The dollar sign thing would be a lot easier. I can't get this to work.
I'm using a db manager where I can just use ' instead of \'. How would
it look for that? In other words, it doesn't have the "create or
replace function as ' --stuff ' language 'plpgsql'" it just has the
actual function. Makes things a little easier. I'm getting an error at
or near "5".
>
> because pre-8.0 the planner won't realize that the inequality is
> selective enough to favor an indexscan, unless it's comparing to
> a simple constant.
>
> (BTW, 8.0's dollar quoting makes this sort of thing a lot less painful)
>
> regards, tom lane
>
--
-Josh
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Subject: Re: slow queries, possibly disk io
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