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weird behaviour on DISTINCT ON

From: Gaetano Mendola <mendola(at)bigfoot(dot)com>
To: pgsql-hackers(at)postgresql(dot)org
Subject: weird behaviour on DISTINCT ON
Date: 2005-01-31 11:25:13
Message-ID: ctl4im$iib$ (view raw, whole thread or download thread mbox)
Lists: pgsql-hackers
Hi all,
I have a query that is something like this:

SELECT DISTINCT ON ( x ) x, foo(x)
FROM ...

now what do I see is that for each different x value
the foo is executed more than once, I guess this is because
the distinct filter out the rows after executing the query.

Is this behaviour the normal one? Shall be not documented ?

Gaetano Mendola


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