From: Ow Mun Heng <Ow.Mun.Heng@wdc.com>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: Steinar H. Gunderson <sgunderson@bigfoot.com>
Cc: Carlo Stonebanks <stonec.register@sympatico.ca>
Cc: pgsql-performance@postgresql.org
Subject: Re: REPOST: Nested loops row estimates always too high
Date: Thu, 27 Sep 2007 14:59:13 +0800
Message-ID: <1190876353.15634.65.camel@neuromancer.home.net> (raw)
In-Reply-To: <12946.1190779378@sss.pgh.pa.us>
References: <fcu215$2em3$1@news.hub.org>
<1190616376.17050.51.camel@neuromancer.home.net>
<fd8ukj$s38$1@news.hub.org>
<1190681440.22945.8.camel@neuromancer.home.net>
<53877A06E07146D2898619A7025C6107@serenity>
<20070925093133.GA27052@uio.no>
<1190778646.5402.16.camel@neuromancer.home.net>
<12946.1190779378@sss.pgh.pa.us>
On Wed, 2007-09-26 at 00:02 -0400, Tom Lane wrote:
> Ow Mun Heng <Ow.Mun.Heng@wdc.com> writes:
> > Where can I erad more about this new "feature"?
>
> http://developer.postgresql.org/pgdocs/postgres/sql-createfunction.html
>
> http://developer.postgresql.org/pgdocs/postgres/ always has a current
> snapshot of CVS-HEAD documentation...
I read these two items
...
execution_cost
A positive number giving the estimated execution cost for the
function, in units of cpu_operator_cost. If the function returns a set,
this is the cost per returned row. If the cost is not specified, 1 unit
is assumed for C-language and internal functions, and 100 units for
functions in all other languages. Larger values cause the planner to try
to avoid evaluating the function more often than necessary.
result_rows
A positive number giving the estimated number of rows that the
planner should expect the function to return. This is only allowed when
the function is declared to return a set. The default assumption is 1000
rows.
...
[/snip]
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To: pgsql-performance@postgresql.org
Cc: Ow.Mun.Heng@wdc.com, tgl@sss.pgh.pa.us, sgunderson@bigfoot.com, stonec.register@sympatico.ca
Subject: Re: REPOST: Nested loops row estimates always too high
In-Reply-To: <1190876353.15634.65.camel@neuromancer.home.net>
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