DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma;
	h=mime-version:in-reply-to:references:date:message-id:subject:from:to
	:cc:content-type;
	b=E+MdCRUqCFZbR/HcCh0dJLlrrhSgxZ7PXmOlrFoH8oIu6jJGg+mtd1ku4/siJpXDbB
	P+M2o+gIct/gHv868wrJLmij+X9w8XBcsywIOv7+MDQtzMRzT7sKHXjtXrmdTd57quxu
	bNOyYk416a3ga/MOAXlgLKbvigGiOjx4J2fuA=
MIME-Version: 1.0
In-Reply-To: <201010091626.18636.neil.whelchel@gmail.com>
References: <201010091626.18636.neil.whelchel@gmail.com>
Date: Tue, 12 Oct 2010 08:12:53 -0700
Message-ID: <AANLkTimXSWapozrZNdiRXDSm2hdsha1As94NwuS967As@mail.gmail.com>
Subject: Re: Slow count(*) again...
From: bricklen <bricklen@gmail.com>
To: Neil Whelchel <neil.whelchel@gmail.com>
Cc: pgsql-performance@postgresql.org
Content-Type: text/plain; charset=UTF-8

On Sat, Oct 9, 2010 at 4:26 PM, Neil Whelchel <neil.whelchel@gmail.com> wrote:
> Maybe an
> estimate(*) that works like count but gives an answer from the index without
> checking visibility? I am sure that this would be good enough to make a page
> list, it is really no big deal if it errors on the positive side, maybe the
> list of pages has an extra page off the end. I can live with that. What I
> can't live with is taking 13 seconds to get a page of results from 850,000
> rows in a table.
> -Neil-
>

FWIW, Michael Fuhr wrote a small function to parse the EXPLAIN plan a
few years ago and it works pretty well assuming your stats are up to
date.

http://markmail.org/message/gknqthlwry2eoqey