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Re: start on outer join

From: "Thomas G(dot) Lockhart" <lockhart(at)alumni(dot)caltech(dot)edu>
To: Bruce Momjian <maillist(at)candle(dot)pha(dot)pa(dot)us>
Cc: hackers(at)postgreSQL(dot)org
Subject: Re: start on outer join
Date: 1999-02-22 06:56:36
Message-ID: 36D0FFA4.32ADB75C@alumni.caltech.edu (view raw or flat)
Thread:
Lists: pgsql-hackers
Bruce Momjian wrote:
> 
> > Will apply ... some other changes laying a bit of
> > groundwork for outer joins so you can start on the planner/optimizer
> > parts :)
> Those will be a synch now that I understand the optimizer.  In fact, I
> think it all will happen in the executor.

I've modified executor/nodeMergeJoin.c to walk a left/right/both outer
join, but didn't fill in the part which actually creates the result
tuple (which will be the current left- or right-side tuple plus nulls
for filler). I hope this is up your alley :)

So far, I'm not certain what to pass to the planner. The syntax leads me
to pass a select structure from gram.y with a "JoinExpr" structure in
the "fromClause" list. I need to expand that with a combination of
column names and qualifications, but at the time I see the JoinExpr I
don't have access to the top query structure itself. So I may just keep
a modestly transformed JoinExpr to expand later or to pass to the
planner.

btw, the EXCEPT/INTERSECT stuff from Stefan has some ugliness in gram.y
which needs to be fixed (the shift/reduce conflict is not acceptable for
our release version) and some of that code clearly needs to move to
analyze.c or some other module.

                     - Tom

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