From: Jochen Erwied <jochen@pgsql-performance.erwied.eu>
To: Dave Crooke <dcrooke@gmail.com>
Cc: pgsql-performance@postgresql.org
Subject: Re: Possible parser bug? .... Re: Picking out the most recent row using a time stamp column
Date: Fri, 25 Feb 2011 01:03:12 +0100
Message-ID: <1923741490.20110225010312@erwied.eu> (raw)
In-Reply-To: <AANLkTinaxt=xjbxOpXTeoL7SZ6dxJgEU8eDtp2dEbHKq@mail.gmail.com>
References: <AANLkTinaxt=xjbxOpXTeoL7SZ6dxJgEU8eDtp2dEbHKq@mail.gmail.com>
Friday, February 25, 2011, 12:53:08 AM you wrote:
> select distinct on (a, b, c)
> a, b c, time_stamp, value
Without the comma, you declare 'b AS c'
> from data
> order by a, b, c, time_stamp desc;
> The output produced is the same as this query:
> select distinct on (a, b)
> a, b, time_stamp, value
> from data
> order by a, b, time_stamp desc;
the 'c' is optimized away, since it is an alias for b, and thus redundant
for the distinct.
> Not sure if this is considered a parser bug or not, but it feels slightly
> odd not to get an error.
No error, just plain SQL :-)
--
Jochen Erwied | home: jochen@erwied.eu +49-208-38800-18, FAX: -19
Sauerbruchstr. 17 | work: joe@mbs-software.de +49-2151-7294-24, FAX: -50
D-45470 Muelheim | mobile: jochen.erwied@vodafone.de +49-173-5404164
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To: pgsql-performance@postgresql.org
Cc: jochen@pgsql-performance.erwied.eu, dcrooke@gmail.com
Subject: Re: Possible parser bug? .... Re: Picking out the most recent row using a time stamp column
In-Reply-To: <1923741490.20110225010312@erwied.eu>
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