From: Tom Lane <tgl@sss.pgh.pa.us>
To: Andrew Gierth <andrew@tao11.riddles.org.uk>
cc: Michael Paquier <michael@paquier.xyz>, cyg0810@gmail.com,
        pgsql-bugs@lists.postgresql.org
Subject: Re: BUG #17088: FailedAssertion in prepagg.c
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Comments: In-reply-to Andrew Gierth <andrew@tao11.riddles.org.uk>
	message dated "Wed, 07 Jul 2021 22:32:56 +0100"
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Date: Wed, 07 Jul 2021 17:56:12 -0400
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Andrew Gierth <andrew@tao11.riddles.org.uk> writes:
> "Tom" == Tom Lane <tgl@sss.pgh.pa.us> writes:
>  Tom> Hmm. Maybe it'd be better if the default behavior in
>  Tom> expression_tree_walker/mutator did not include recursing into the
>  Tom> args, then?

> You'd think, but as I recall (I will re-check this to confirm) there
> were more places where we _did_ need to recurse (especially during parse
> analysis before we've matched up the sortgrouprefs), while most of the
> places where recursion needed to be explicitly avoided already needed
> special-case handling, so having the default the other way would likely
> have required a special-case almost everywhere.

Fair enough.  This is the kind of design choice that can be worth
revisiting later; but if the conclusion is still the same, fine with me.

			regards, tom lane