Re: row filtering for logical replication

From: "Euler Taveira" <euler(at)eulerto(dot)com>
To: "Tomas Vondra" <tomas(dot)vondra(at)enterprisedb(dot)com>, "Alvaro Herrera" <alvherre(at)alvh(dot)no-ip(dot)org>
Cc: "Dilip Kumar" <dilipbalaut(at)gmail(dot)com>, "Amit Kapila" <amit(dot)kapila16(at)gmail(dot)com>, "Peter Smith" <smithpb2250(at)gmail(dot)com>, "Rahila Syed" <rahilasyed90(at)gmail(dot)com>, "Peter Eisentraut" <peter(dot)eisentraut(at)enterprisedb(dot)com>, Önder Kalacı <onderkalaci(at)gmail(dot)com>, japin <japinli(at)hotmail(dot)com>, "Michael Paquier" <michael(at)paquier(dot)xyz>, "David Steele" <david(at)pgmasters(dot)net>, "Craig Ringer" <craig(at)2ndquadrant(dot)com>, "Tomas Vondra" <tomas(dot)vondra(at)2ndquadrant(dot)com>, "Amit Langote" <amitlangote09(at)gmail(dot)com>, "PostgreSQL Hackers" <pgsql-hackers(at)lists(dot)postgresql(dot)org>
Subject: Re: row filtering for logical replication
Date: 2021-07-14 17:25:20
Message-ID: cd3ee2ae-97e0-45c1-ab33-b2bc03760887@www.fastmail.com
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On Wed, Jul 14, 2021, at 12:08 PM, Tomas Vondra wrote:
> Yeah, but AFAIK that's needed only when replicating DELETEs, so perhaps
> we could ignore this for subscriptions without DELETE.
... and UPDATE. It seems we have a consensus to use old row in the row filter
for UPDATEs. I think you meant publication.

> The other question is when to check/enforce this. I guess we'll have to
> do that during decoding, not just when the publication is being created,
> because the user can do ALTER TABLE later.
I'm afraid this check during decoding has a considerable cost. If we want to
enforce this condition, I suggest that we add it to CREATE PUBLICATION, ALTER
PUBLICATION ... ADD|SET TABLE and ALTER TABLE ... REPLICA IDENTITY. Data are
being constantly modified; schema is not.

--
Euler Taveira
EDB https://www.enterprisedb.com/

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