Re: filtering after join

From: Peter Eisentraut <peter_e(at)gmx(dot)net>
To: pgsql-sql(at)postgresql(dot)org
Cc: andrew <andrew(dot)ylzhou(at)gmail(dot)com>
Subject: Re: filtering after join
Date: 2006-01-25 19:11:13
Message-ID: 200601252011.13465.peter_e@gmx.net
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andrew wrote:
> I want to use a UDF to filter tuples t that are generated after a
> join. More specifially, I have a UDF foo(record), which computes a
> value for a given tuple. I can do the filtering before the join.
> e.g.:
>
> select * from A, B where foo(A)<2 and A.a=B.b;

What makes you think that the filtering happens before the join here?
And why would it matter? The results should be all the same.

--
Peter Eisentraut
http://developer.postgresql.org/~petere/

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