Thread

Re: Proposal: Conflict log history table for Logical Replication

vignesh C <vignesh21@gmail.com> — 2026-05-12T06:00:54Z

On Mon, 11 May 2026 at 11:51, shveta malik <shveta.malik@gmail.com> wrote:
>
> Few comments on 001:
> 3)
> Currently the structure of CLT is:
>
> +const ConflictLogColumnDef ConflictLogSchema[] = {
> + { .attname = "relid",            .atttypid = OIDOID },
> + { .attname = "schemaname",       .atttypid = TEXTOID },
> + { .attname = "relname",          .atttypid = TEXTOID },
> + { .attname = "conflict_type",    .atttypid = TEXTOID },
> + { .attname = "remote_xid",       .atttypid = XIDOID },
> + { .attname = "remote_commit_lsn",.atttypid = LSNOID },
> + { .attname = "remote_commit_ts", .atttypid = TIMESTAMPTZOID },
> + { .attname = "remote_origin",    .atttypid = TEXTOID },
> + { .attname = "replica_identity", .atttypid = JSONOID },
> + { .attname = "remote_tuple",     .atttypid = JSONOID },
> + { .attname = "local_conflicts",  .atttypid = JSONARRAYOID }
> +};
>
> So if user has to delete a conflict from CLT after resolving it, then
> what is the user-friendly way to do it? IMO, it will be cumbersome
> (and perhaps error-prone) to write a query with remote_commit_lsn,
> remote_commit_ts, remote_xid etc in WHERE clause. Do you (or others)
> think we shall add a log_id column (perhaps a bigint GENERATED ALWAYS
> AS IDENTITY). This provides a simple, unique identifier so the user
> can easily target a single row (WHERE log_id = 105) or purge a batch
> of old conflicts (WHERE log_id < 1000).

I agree with this. I could think of a few other possible approaches as well.
The following options seem possible to make row identification/deletion easier:
a) Use existing remote_commit_ts
ex:
DELETE FROM pg_conflict.pg_conflict_log_16400 WHERE remote_commit_ts =
'2026-05-12 10:25:46.483899+05:30';
DELETE FROM pg_conflict.pg_conflict_log_16400 WHERE remote_commit_ts <
now() - interval '100 minutes';
b) Use existing system column ctid
ex:
DELETE FROM pg_conflict.pg_conflict_log_16400 WHERE ctid = '(0,1)';
c) Add a dedicated identifier conflict_id column as Shveta said
DELETE FROM pg_conflict.pg_conflict_log_16400 WHERE conflict_id = 42;
DELETE FROM pg_conflict.pg_conflict_log_16400 WHERE conflict_id < 100;
d) Add a local conflict_logged_at timestamp
DELETE FROM pg_conflict.pg_conflict_log_16400 WHERE conflict_logged_at
= '2026-05-12 10:25:46.483899+05:30';
DELETE FROM pg_conflict.pg_conflict_log_16400 WHERE conflict_logged_at
< now() - interval '100 minutes';

I'm not sure which approach would be best here.
Thoughts?

Regards,
Vignesh