From: Tom Lane <tgl@sss.pgh.pa.us>
To: Bruno Wolff III <bruno@wolff.to>
Cc: Enver ALTIN <enver.altin@frontsite.com.tr>
Cc: pgsql-sql@postgresql.org
Subject: Re: randomized order in select?
Date: Thu, 11 Mar 2004 01:40:06 -0500
Message-ID: <16599.1078987206@sss.pgh.pa.us> (raw)
In-Reply-To: <20040310190250.GA6629@wolff.to>
References: <1078937297.29628.12.camel@enver.office.frontsite.com.tr>
<20040310190250.GA6629@wolff.to>
Bruno Wolff III <bruno@wolff.to> writes:
> Enver ALTIN <enver.altin@frontsite.com.tr> wrote:
>> I wish I could do something like:
>> select tiptext from tips order by random limit 1
>> in PostgreSQL.
> You can but it won't be very efficient (for large tables) as it will generate
> a random ordering for the whole table, probably do a sort and then return the
> first record. The only thing different you need to do is add () after random:
> select tiptext from tips order by random() limit 1
If you do need to do this for a large table, I seem to recall that
we've previously worked out reasonable ways to select a random entry
efficiently using an index. Dig around in the mail list archives for
details.
regards, tom lane
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To: pgsql-sql@postgresql.org
Cc: tgl@sss.pgh.pa.us, bruno@wolff.to, enver.altin@frontsite.com.tr
Subject: Re: randomized order in select?
In-Reply-To: <16599.1078987206@sss.pgh.pa.us>
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