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Subject: Re: Improve logical replication usability when tables lack primary
 keys
From: Chao Li <li.evan.chao@gmail.com>
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Date: Tue, 14 Apr 2026 14:19:46 +0800
Cc: Euler Taveira <euler@eulerto.com>,
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To: shveta malik <shveta.malik@gmail.com>,
 Amit Kapila <amit.kapila16@gmail.com>
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> On Apr 14, 2026, at 13:49, shveta malik <shveta.malik@gmail.com> =
wrote:
>=20
> On thinking more about the initial design with a GUC-based approach, I
> believe we already have a similar precedent where both a GUC and a
> table/column-level property coexist. For example, the
> default_toast_compression GUC allows setting a default compression
> method globally, while users can still override it at the column level
> during CREATE TABLE or ALTER TABLE. A similar approach could work in
> our case as well.

Thanks for pointing out this.

Yes, one of solutions I initially considered was to introduce a GUC, say =
default_replica_identity_fallback, with a default value of =E2=80=9CNONE=E2=
=80=9D, which is the current behavior. We just need to support one more =
value =E2=80=9CFULL=E2=80=9D, then when a table has no primary key, its =
replica identity falls back to FULL. Users may freely set the table's =
replica identity to any value. And the database administrator can set =
the GUC at either cluster level or database level based on their =
operation practices.

>=20
> Regarding the publication-level property, apart from the potential
> data-integrity issues discussed earlier, I also have another concern.
> If we introduce a publication-level fallback, we would effectively be
> deciding what gets logged in WAL for a particular table (i.e., whether
> to log REPLICA IDENTITY FULL) based on a publication parameter. This
> does not seem quite right to me. Shouldn't WAL logging typically be
> independent of publication configuration? Or do we already have a case
> where WAL logging behavior depends on publication-level properties?
>=20
> Thanks,
> Shveta

For this, I really want to hear back from Amit.

Best regards,
--
Chao Li (Evan)
HighGo Software Co., Ltd.
https://www.highgo.com/