From: Tom Lane <tgl@sss.pgh.pa.us>
To: Tomas Vondra <tomas.vondra@2ndquadrant.com>
cc: buschmann@nidsa.net, pgsql-bugs@lists.postgresql.org
Subject: Re: BUG #16045: vacuum_db crash and illegal memory alloc after
 pg_upgrade from PG11 to PG12
In-reply-to: <20191009232836.jg77wccqwy5fgs6s@development>
References: <16045-673e8fa6b5ace196@postgresql.org>
 <20191009132436.uugh4r3be6vw6ex4@development>
 <20191009135907.km2b5nrzflcz6xey@development>
 <20191009141841.my6k44wfiaquj3ks@development>
 <20191009230759.ge66neof5qj627a2@development>
 <19314.1570663125@sss.pgh.pa.us>
 <20191009232836.jg77wccqwy5fgs6s@development>
Comments: In-reply-to Tomas Vondra <tomas.vondra@2ndquadrant.com>
	message dated "Thu, 10 Oct 2019 01:28:36 +0200"
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Date: Wed, 09 Oct 2019 19:41:54 -0400
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Tomas Vondra <tomas.vondra@2ndquadrant.com> writes:
> On Wed, Oct 09, 2019 at 07:18:45PM -0400, Tom Lane wrote:
>> Fortunately, there should be close to zero people with user tables
>> depending on sql_identifier.  I think we should just add a test in
>> pg_upgrade that refuses to upgrade if there are any such columns.
>> It won't be the first such restriction.

> Hmmm, yeah.  I agree the number of people using sql_identifier in user
> tables is low, but OTOH we got this report within a week after release,
> so maybe it's higher than we think.

True.

> Another option would be to teach pg_upgrade to switch the columns to
> 'text' or 'varchar', not sure if that's possible or how much work would
> that be.

I think it'd be a mess --- the actual hacking would have to happen in
pg_dump, I think, and it'd be a kluge because pg_dump doesn't normally
understand what server version its output is going to.  So we'd more
or less have to control it through a new pg_dump switch that pg_upgrade
would use.  Ick.

Also, even if we did try to silently convert such columns that way,
I bet we'd get other bug reports about "why'd my columns suddenly
change type?".  So I'd rather force the user to be involved.

			regards, tom lane