From: Daniel Gustafsson <daniel@yesql.se>
To: Tom Lane <tgl@sss.pgh.pa.us>
Cc: David G. Johnston <david.g.johnston@gmail.com>
Cc: zedaardv@drizzle.com <zedaardv@drizzle.com>
Cc: pgsql-bugs@lists.postgresql.org <pgsql-bugs@lists.postgresql.org>
Subject: Re: BUG #17720: pg_dump creates a dump with primary key that cannot be restored, when specifying 'using index ...'
Date: Wed, 14 Dec 2022 16:51:09 +0100
Message-ID: <36765FCD-2CE4-40C2-80D3-7A7076B68DB1@yesql.se> (raw)
In-Reply-To: <2684951.1671032222@sss.pgh.pa.us>
References: <17720-dab8ee0fa85d316d@postgresql.org>
<CAKFQuwam=1NoSNH=EJRUnuuD8JE_jM8tq22-SYqO1nxzoXFwzg@mail.gmail.com>
<9C039DE3-EFBD-4D65-B4CF-90D8148B7B4C@yesql.se>
<2684951.1671032222@sss.pgh.pa.us>
> On 14 Dec 2022, at 16:37, Tom Lane <tgl@sss.pgh.pa.us> wrote:
>
> Daniel Gustafsson <daniel@yesql.se> writes:
>> On 14 Dec 2022, at 13:54, David G. Johnston <david.g.johnston@gmail.com> wrote:
>>> There is a decent chance that the fix here is to prohibit doing what you did here - a PK cannot contain nulls in any of its columns so indeed choosing an index that specifies how nulls behave is non-sensical. That said, it also doesn’t hurt so long as the column itself is indeed not null. But extending the syntax doesn’t seem that appealing.
>
>> Even if we prohibit this, there is still the case of all existing systems which
>> can't be dumped. I wonder if the solution is to teach pg_dump to not create
>> NULLS NOT DISTINCT primary key constraints? The simple attached fix creates a
>> valid PK constraint on the above schema.
>
> It doesn't make sense for pg_dump to editorialize on a schema that
> we otherwise consider valid; people would rightfully complain that
> dump/restore changed things. So we need to do both things: prohibit
> adopting such an index as a PK constraint (but I guess it's okay
> for plain unique constraints?), and adjust pg_dump to compensate
> for the legacy case where it was already done.
Agreed, I'll expand the patch.
--
Daniel Gustafsson https://vmware.com/
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To: pgsql-bugs@postgresql.org
Cc: daniel@yesql.se, tgl@sss.pgh.pa.us, david.g.johnston@gmail.com, zedaardv@drizzle.com, pgsql-bugs@lists.postgresql.org
Subject: Re: BUG #17720: pg_dump creates a dump with primary key that cannot be restored, when specifying 'using index ...'
In-Reply-To: <36765FCD-2CE4-40C2-80D3-7A7076B68DB1@yesql.se>
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