From: | Bruce Momjian <maillist(at)candle(dot)pha(dot)pa(dot)us> |
---|---|
To: | lockhart(at)alumni(dot)caltech(dot)edu (Thomas G(dot) Lockhart) |
Cc: | hackers(at)postgreSQL(dot)org |
Subject: | Re: OUTER joins |
Date: | 1999-03-07 03:25:31 |
Message-ID: | 199903070325.WAA10357@candle.pha.pa.us |
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Lists: | pgsql-hackers |
> (back from a short vacation...)
>
> > How do you propose doing outer joins in non-mergejoin situations?
> > Mergejoins can only be used currently in equal joins.
>
> Hadn't thought about it, other than figuring that implementing the
> equi-join first was a good start. There is a class of outer join syntax
> (the USING clause) which is implicitly an equi-join...
Not that easy. You don't automatically get a mergejoin from an
equijoin. I will have to force outer's to be either mergejoins, or
inners of non-merge joins. Can you add code to non-merge joins in the
executor to throw out a null row if it does not find an inner match for
the outer row, and I will handle the optimizer so it doesn't throw a
non-conforming plan to the executor.
--
Bruce Momjian | http://www.op.net/~candle
maillist(at)candle(dot)pha(dot)pa(dot)us | (610) 853-3000
+ If your life is a hard drive, | 830 Blythe Avenue
+ Christ can be your backup. | Drexel Hill, Pennsylvania 19026
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