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Re: Slow views

From: David Newall <davidn-postgres(at)rebel(dot)net(dot)au>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: PostgreSQL bugs <pgsql-bugs(at)postgresql(dot)org>
Subject: Re: Slow views
Date: 2004-07-17 07:37:01
Message-ID: 1090049818.12051.116.camel@localhost.localdomain (view raw or flat)
Thread:
Lists: pgsql-bugs
On Sat, 2004-07-17 at 14:30, Tom Lane wrote:
> David Newall <davidn-postgres(at)rebel(dot)net(dot)au> writes:
> > select * from a join b optimises differently to select * from a join
> > (select * from b) as b
> 
> The above claim is provably false.  Now, if you throw in some more
> tables and sprinkle in a LEFT JOIN instead of just JOIN here and there,
> you can get different plans --- but the semantics are not necessarily
> the same, either.

You're right.  It's select * from a left join b left join c that
optimises differently to select * from a left join (select * from b left
join c).  I was clumsy with my language but I think my meaning was clear
within the context of this thread.  Anyway, back to my point: I'd like
to use a view but I can't because it's too slow, and that's a pity.


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