Re: Optimisation of INTERSECT expressions - Mailing list pgsql-performance

From Tom Lane
Subject Re: Optimisation of INTERSECT expressions
Date
Msg-id 20715.1080056862@sss.pgh.pa.us
Whole thread Raw
In response to Re: Optimisation of INTERSECT expressions  (Stephan Szabo <sszabo@megazone.bigpanda.com>)
List pgsql-performance
Stephan Szabo <sszabo@megazone.bigpanda.com> writes:
> Given a non-unique A, C1 as B>5, c2 as C>5 and the data:
> A | B | C
> 1 | 6 | 1
> 1 | 1 | 6
> The intersect gives 1 row, the and query gives 0 AFAICS.

Another way that the queries are not equivalent is that INTERSECT is
defined to remove duplicate output rows (much like DISTINCT) whereas
the AND form of course won't do that.

            regards, tom lane

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