| From: | Simon Riggs <simon(at)2ndquadrant(dot)com> |
|---|---|
| To: | Matthew Wakeling <matthew(at)flymine(dot)org> |
| Cc: | pgsql-performance <pgsql-performance(at)postgresql(dot)org> |
| Subject: | Re: Outer joins and equivalence |
| Date: | 2008-05-28 13:39:10 |
| Message-ID: | 1211981950.4489.473.camel@ebony.site |
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| Thread: | |
| Lists: | pgsql-hackers pgsql-performance |
On Wed, 2008-05-28 at 11:45 +0100, Matthew Wakeling wrote:
> On Tue, 27 May 2008, Simon Riggs wrote:
> > I do recognise that we would *not* be able to deduce this form of SQL
> >
> > A JOIN B ON (a.id = c.id) LEFT JOIN C ON (b.id = c.id)
>
> Surely that would not be valid SQL?
You are right, but my point was about inferences during SQL planning,
not about initial analysis of the statement.
--
Simon Riggs www.2ndQuadrant.com
PostgreSQL Training, Services and Support
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