From: Gregory Stark <stark@enterprisedb.com>
To: Andreas Joseph Krogh <andreak@officenet.no>
Cc: pgsql-sql@postgresql.org
Cc: Tom Lane <tgl@sss.pgh.pa.us>
Subject: Re: Returning the total number of rows as a separate column when using limit
Date: Tue, 06 Nov 2007 06:58:59 +0000
Message-ID: <873avjx3kc.fsf@oxford.xeocode.com> (raw)
In-Reply-To: <87fxzkwmir.fsf@oxford.xeocode.com>
References: <200711050836.38130.andreak@officenet.no>
<19503.1194274853@sss.pgh.pa.us>
<87ir4g67co.fsf@oxford.xeocode.com>
<200711051733.10324.andreak@officenet.no>
<87fxzkwmir.fsf@oxford.xeocode.com>
"Gregory Stark" <stark@enterprisedb.com> writes:
> "Andreas Joseph Krogh" <andreak@officenet.no> writes:
>
>> That's what I'm doing now. I run the query with "limit+1" as limit and if it
>> results in more than limit, I know there is more data and I run count(*) to
>> count them all. But count(*) cannot use indices in PG so it's limited in
>> speed anyway AFAICS.
>
> Well count(*) can use indexes the same as the query can.
>
>> I really hoped there was an "Oracle over()" equivalent way in PG. I understand
>> that Oracle's LIMIT-hack with "3 subselects and rownum between 1 AND 20" is
>> rather expensive compared to PG's implementation of LIMIT. Oralce keeps
>> snapshot-info in the index, so counting only involves the index AFAIK.
>
> Well that's only going to be true if the index satisfies the whole query which
> is not going to be true for the simplest cases.
er, *except* for the simplest cases.
--
Gregory Stark
EnterpriseDB http://www.enterprisedb.com
Ask me about EnterpriseDB's RemoteDBA services!
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To: pgsql-sql@postgresql.org
Cc: stark@enterprisedb.com, andreak@officenet.no, tgl@sss.pgh.pa.us
Subject: Re: Returning the total number of rows as a separate column when using limit
In-Reply-To: <873avjx3kc.fsf@oxford.xeocode.com>
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