From: Tom Lane <tgl@sss.pgh.pa.us>
To: Richard Guo <guofenglinux@gmail.com>
cc: tharakan@gmail.com, pgsql-bugs@lists.postgresql.org
Subject: Re: BUG #17768: Assert triggered on initsplan.c
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Comments: In-reply-to Richard Guo <guofenglinux@gmail.com>
	message dated "Thu, 02 Feb 2023 20:02:44 +0800"
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Date: Thu, 02 Feb 2023 19:47:25 -0500
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Richard Guo <guofenglinux@gmail.com> writes:
>> There is something wrong about postponing quals.  We are supposed to
>> postpone quals only from children to their parent nodes.  But here in
>> deconstruct_distribute we scan all the jointree nodes in depth-first
>> traversal order and any quals postponed by left children may be checked
>> against right children.  If the right subtree is an outer join as in
>> this example, the assertion would be triggered.

> To fix this issue, I'm considering that we can add two types of info in
> JoinTreeItem for each jointree node, one is the jointree's children, and
> one is the list of quals that need to be postponed at this join level.
> Thus in deconstruct_distribute we can process the quals postponed by
> children.

I've not looked closely at this, but ... I remember thinking while
revising deconstruct_jointree that the whole PostponedQual mechanism
was a wart we should try to get rid of.  I didn't touch it since
I saw no obvious bugs and the patch was too large already, but maybe
now is the time to try harder.  In any case I suspect you are right
that the core of this issue is that we're dealing with PostponedQuals
in the wrong order now.

			regards, tom lane