From: | Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | Christopher Kings-Lynne <chriskl(at)familyhealth(dot)com(dot)au>, pgsql-hackers(at)postgresql(dot)org |
Subject: | Re: Fixing row comparison semantics |
Date: | 2005-12-26 05:15:12 |
Message-ID: | 200512260515.jBQ5FCO09783@candle.pha.pa.us |
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Lists: | pgsql-hackers |
Tom Lane wrote:
> Christopher Kings-Lynne <chriskl(at)familyhealth(dot)com(dot)au> writes:
> > Can someone explain to me how:
> > (a, b) < (1, 2)
> > is different to
> > a < 1 and b < 2
>
> Right at the moment our code interprets it that way, but this behavior
> is wrong per spec. It should be an ordered column-by-column comparison,
> so that the equivalent simple expression is
>
> (a < 1) OR (a = 1 AND b < 2)
TODO updated:
* %Make row-wise comparisons work per SQL spec
Right now, '(a, b) < (1, 2)' is processed as 'a < 1 and b < 2', but
the SQL standard requires it to be processed as a column-by-column
comparison, so the proper comparison is '(a < 1) OR (a = 1 AND b < 2)'
--
Bruce Momjian | http://candle.pha.pa.us
pgman(at)candle(dot)pha(dot)pa(dot)us | (610) 359-1001
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