From: Tom Lane <tgl@sss.pgh.pa.us>
To: Stephen Frost <sfrost@snowman.net>
cc: Robert Haas <robertmhaas@gmail.com>, Sergei Kornilov <sk@zsrv.org>,
        "pgsql-hackers@postgresql.org" <pgsql-hackers@postgresql.org>
Subject: Re: using index or check in ALTER TABLE SET NOT NULL
In-reply-to: <20171129152135.GN4628@tamriel.snowman.net>
References: <81911511895540@web58j.yandex.ru>
 <CA+TgmoZKR4dTR7KyoM4jfJN2J-eNoBRG2_XHdZa1f0VUbK1xXQ@mail.gmail.com>
 <20171129152135.GN4628@tamriel.snowman.net>
Comments: In-reply-to Stephen Frost <sfrost@snowman.net>
	message dated "Wed, 29 Nov 2017 10:21:35 -0500"
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Date: Wed, 29 Nov 2017 10:47:21 -0500
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Stephen Frost <sfrost@snowman.net> writes:
> Isn't the first concern addressed by using SPI..?

I did not look at the patch yet, but TBH if it uses SPI for sub-operations
of ALTER TABLE I think that is sufficient reason to reject it out of hand.
Doing things that way would create way too much of a vulnerability surface
for code touching a partially-updated table.  At minimum, we'd have to
blow holes in existing protections like CheckTableNotInUse, and I think
we'd be forever finding other stuff that failed to work quite right in
that context.  I do not want ALTER TABLE going anywhere near the planner
or executor; I'm not even happy that it uses the parser (for index
definition reconstruction).

			regards, tom lane