From: Bill Moran <wmoran@collaborativefusion.com>
To: Robins Tharakan <tharakan@gmail.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: count * performance issue
Date: Tue, 11 Mar 2008 09:35:37 -0400
Message-ID: <20080311093537.a60e2e3d.wmoran@collaborativefusion.com> (raw)
In-Reply-To: <36af4bed0803101957u6078127fq78dc3384fe78de5d@mail.gmail.com>
References: <f966c2ee0803052142l6a105678jfe2da92a0d9371@mail.gmail.com>
<47D00DB2.7040007@emolecules.com>
<18451.1204824562@sss.pgh.pa.us>
<200803071727.36146.josh@agliodbs.com>
<13345.1204940295@sss.pgh.pa.us>
<87r6eia9tz.fsf@oxford.xeocode.com>
<12ba3bf00803101354w15b023e1o237f564a1b01105f@mail.gmail.com>
<Pine.GSO.4.64.0803101853090.25041@westnet.com>
<36af4bed0803101957u6078127fq78dc3384fe78de5d@mail.gmail.com>
In response to "Robins Tharakan" <tharakan@gmail.com>:
> Hi,
>
> I have been reading this conversation for a few days now and I just wanted
> to ask this. From the release notes, one of the new additions in 8.3 is
> (Allow col IS NULL to use an index (Teodor)).
>
> Sorry, if I am missing something here, but shouldn't something like this
> allow us to get a (fast) accurate count ?
>
> SELECT COUNT(*) from table WHERE indexed_field IS NULL
> +
> SELECT COUNT(*) from table WHERE indexed_field IS NOT NULL
For certain, qualified definitions of "fast", sure.
--
Bill Moran
Collaborative Fusion Inc.
http://people.collaborativefusion.com/~wmoran/
wmoran@collaborativefusion.com
Phone: 412-422-3463x4023
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To: pgsql-performance@postgresql.org
Cc: wmoran@collaborativefusion.com, tharakan@gmail.com
Subject: Re: count * performance issue
In-Reply-To: <20080311093537.a60e2e3d.wmoran@collaborativefusion.com>
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