From: paul socha <pawel.socha@gmail.com>
To: emilu@encs.concordia.ca
Cc: pgsql-performance@postgresql.org
Subject: Re: update - which way quicker?
Date: Thu, 28 Aug 2008 23:13:55 +0200
Message-ID: <A826B099-A9BA-4CDF-A7BA-AAB0BC739E67@gmail.com> (raw)
In-Reply-To: <48B6FCF8.3090807@encs.concordia.ca>
References: <48B6FCF8.3090807@encs.concordia.ca>
On 2008-08-28, at 21:31, Emi Lu wrote:
> Good morning,
>
> Tried to compare Table1 based on Table2
>
> . update table1.col = false
> if table1.pk_cols not in table2.pk_cols
>
>
>
> For the following two ways, (2) always performs better than (1) right,
> and I need your inputs.
> ======================================================================
> ==
> (1) update table1
> set col = false
> where table1.pk_co1 || table1.pk_col2.... || table1.pk_colN
>
> NOT IN
>
> (select pk_co1 || pk_col2.... || pk_colN
> from table2
> )
>
> (2) ResultSet(rs) =
> select pk_col1||pk_col2... || pk_colN
> from table1
> left join table2 using (pk_col1..., pk_colN)
> where table2.pk_col1 is null
>
> Then for each rs record, do:
> update table1
> set col = false
> where col1||... colN in rs.value
>
> Thanks a lot!
>
> --
> Sent via pgsql-performance mailing list (pgsql-
> performance@postgresql.org)
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Check EXISTS
http://www.postgresql.org/docs/8.3/interactive/functions-subquery.html
Serdecznie pozdrawiam
Pawel Socha
pawel.socha@gmail.com
programista/administrator
perl -le 's**02).4^&-%2,).^9%4^!./4(%2^3,!#+7!2%^53%2&**y%& -;^[%"`-
{ a%%s%%$_%ee'
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To: pgsql-performance@postgresql.org
Cc: pawel.socha@gmail.com, emilu@encs.concordia.ca
Subject: Re: update - which way quicker?
In-Reply-To: <A826B099-A9BA-4CDF-A7BA-AAB0BC739E67@gmail.com>
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