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Re: Proposal: Conflict log history table for Logical Replication

shveta malik <shveta.malik@gmail.com>

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From: shveta malik <shveta.malik@gmail.com>
To: vignesh C <vignesh21@gmail.com>
Cc: Dilip Kumar <dilipbalaut@gmail.com>, Amit Kapila <amit.kapila16@gmail.com>, Masahiko Sawada <sawada.mshk@gmail.com>, Bharath Rupireddy <bharath.rupireddyforpostgres@gmail.com>, PostgreSQL Hackers <pgsql-hackers@lists.postgresql.org>, shveta malik <shveta.malik@gmail.com>
Date: 2025-12-22T10:34:05Z
Lists: pgsql-hackers

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  1. Allow logical replication conflicts to be logged to a table.

  2. Avoid orphaned objects dependencies

On Mon, Dec 22, 2025 at 3:55 PM vignesh C <vignesh21@gmail.com> wrote:
>
>
> Few comments:
> 1) when a conflict_log_destination is specified as log:
> create subscription sub1 connection 'dbname=postgres host=localhost
> port=5432' publication pub1 with ( conflict_log_destination='log');
> postgres=# select subname, subconflictlogrelid,sublogdestination from
> pg_subscription where subname = 'sub4';
>  subname | subconflictlogrelid | sublogdestination
> ---------+---------------------+-------------------
>  sub4    |                   0 | log
> (1 row)
>
> Currently it displays as 0, instead we can show as NULL in this case

I also thought about it while reviewing, but I feel 0 makes more sense
as it is 'relid'. This is how it is shown currently in other tables.
See 'reltoastrelid':

postgres=# select relname, reltoastrelid from  pg_class where relname='tab1';
 relname | reltoastrelid
---------+---------------
 tab1    |             0
(1 row)


>
> 3) Can we include pg_ in the conflict table to indicate it is an
> internally created table:
> +/*
> + * Format the standardized internal conflict log table name for a subscription
> + *
> + * Use the OID to prevent collisions during rename operations.
> + */
> +void
> +GetConflictLogTableName(char *dest, Oid subid)
> +{
> +       snprintf(dest, NAMEDATALEN, "conflict_log_table_%u", subid);
> +}
>

There is already a discussion about it in [1]

[1]: https://www.postgresql.org/message-id/CAA4eK1KE%3DtNHcN3Qp0FZVwDnt4rF2zwHy8NgAdG3oPqixdzOsA%40mail.gmail.com

thanks
Shveta