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Re: Proposal for supporting outer joins in 7.1

From: Philip Warner <pjw(at)rhyme(dot)com(dot)au>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, pgsql-hackers(at)postgreSQL(dot)org
Subject: Re: Proposal for supporting outer joins in 7.1
Date: 2000-08-27 09:56:57
Message-ID: 3.0.5.32.20000827195657.02ac8100@mail.rhyme.com.au (view raw or flat)
Thread:
Lists: pgsql-hackers
At 16:07 25/08/00 -0400, Tom Lane wrote:
> For example:
>
>SELECT ... FROM a,b,c
>	Planner will consider all three possible join orders:
>	(a cross join b) cross join c
>	(a cross join c) cross join b
>	(b cross join c) cross join a
>
>SELECT ... FROM (a cross join b) cross join c
>	Planner will only consider joining a with b and then adding c.
>

I'm not sure whether the above is the syntax you plan to use, but it looks
a little too much like:

SELECT ... FROM (select * from a cross join b) as z cross join c

which has a quite different meaning to any kind of outer join, and the
parenthesis, in this case, should not affect the planner choices. I don;t
think that support for this kind of query is implemented, but it could
confuse things a little.

As an aside, while you are in there, I don't suppose you would be able to
implement that above syntax as well? Then, maybe, have a go at the common
cold, too.


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