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Re: COALESCE implementation question

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: Philip Warner <pjw(at)rhyme(dot)com(dot)au>
Cc: pgsql-hackers(at)hub(dot)org
Subject: Re: COALESCE implementation question
Date: 2000-08-06 04:50:17
Message-ID: 23985.965537417@sss.pgh.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackers
Philip Warner <pjw(at)rhyme(dot)com(dot)au> writes:
>> This is a bug caused by interaction between two planning passes run
>> on the same Query node.  The parser thinks it's cool to generate a
>> CASE parsetree with multiple paths to the same sub-select Query node,
>> but in fact it is not cool because planning destructively alters the
>> Query node contents.  I'm amazed it didn't crash, to tell the truth.
>> 
>> I have a patch but haven't applied it yet (been offline for most of
>> two days due to telco idiocy :-().

> Thanks for this; I must admit I was very surprised not to get a response
> withing 24 hours! Is there any chance of sending me the patch - I have been
> looking at the sources for a while now, and it would be nice to see the
> answer...

Well, I'm not *proud* of this patch, it's pretty much brute-force.
But it will do until we get around to redesigning querytrees.
See src/backend/optimizer/plan/subselect.c.

I imagine the diff would apply to 7.0.* if you want to do that.

			regards, tom lane

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