From: Tom Lane <tgl@sss.pgh.pa.us>
To: "David G. Johnston" <david.g.johnston@gmail.com>
cc: "pgsql-hackers@lists.postgresql.org" <pgsql-hackers@lists.postgresql.org>
Subject: Re: Further cleanup of pg_dump/pg_restore item selection code
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Comments: In-reply-to "David G. Johnston" <david.g.johnston@gmail.com>
	message dated "Wed, 24 Jan 2018 20:36:05 -0700"
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Date: Wed, 24 Jan 2018 23:17:38 -0500
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"David G. Johnston" <david.g.johnston@gmail.com> writes:
> On Wednesday, January 24, 2018, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>> The same behaviors occur if you do e.g.
>> 	pg_dump -Fc -t sometable somedb | pg_restore --create
>> which is another undocumented misbehavior: the docs for pg_restore do not
>> suggest that --create might fail if the source archive was selective.

> pg_restore -t:

> "When -t is specified, pg_restore makes no attempt to restore any other
> database objects that the selected table(s) might depend upon. Therefore,
> there is no guarantee that a specific-table restore into a clean database
> will succeed."

I think you might be missing one of the main points here, which is
that --create is specified as causing both a CREATE DATABASE and a
reconnect to that database.  If it silently becomes a no-op, which
is what happens today, the restore is likely to go into the wrong
database entirely (or at least not the DB the user expected).

I won't deny the possibility that some people are depending on the
existing wrong behavior, but that's a hazard with any bug fix.

			regards, tom lane