From: Andreas Joseph Krogh <andreak@officenet.no>
Organization: OfficeNet AS
To: pgsql-sql@postgresql.org
Subject: Re: Returning the total number of rows as a separate column when
	using limit
Date: Mon, 5 Nov 2007 15:38:34 +0100
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Cc: Tom Lane <tgl@sss.pgh.pa.us>
References: <200711050836.38130.andreak@officenet.no>
	<18728.1194272302@sss.pgh.pa.us>
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On Monday 05 November 2007 15:18:22 Tom Lane wrote:
> Andreas Joseph Krogh <andreak@officenet.no> writes:
> > AFAICS the information about the *total* number of rows is in the
> > "result" somehow. When I execute a "limit 1" query with EXPLAIN ANALYZE,
> > I se the total number of columns in "rows=3D200819", so the information=
 is
> > there.
>
> That's only an estimate.  Since the query doesn't get executed to
> completion thanks to the LIMIT, Postgres really has no idea whether
> the estimate is accurate.

Ok. The query is ORDER-ed, but you're saying that it doesn't matter and PG=
=20
still doesn't have to know the total numbers even if it has to sort the=20
result?

Is there a way to perform the LIMIT-query only once and still be able to=20
extract the total number of rows from some "magic function", like=20
Oracle's "over()" analytic function? I will accept a simple "no" if that is=
=20
the case, but if it is possible (like it is in Oracle) I would appreciate t=
o=20
know how to do it.

=2D-=20
Andreas Joseph Krogh <andreak@officenet.no>
Senior Software Developer / Manager
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