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Fix duplicate transaction replay during pg_createsubscriber.

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Previously, the tool could replay the same transaction twice, once during
recovery, then again during replication after the subscriber was set up.

This occurred because the same recovery_target_lsn was used both to
finalize recovery and to start replication. If
recovery_target_inclusive = true, the transaction at that LSN would be
applied during recovery and then sent again by the publisher leading to
duplication.

To prevent this, we now set recovery_target_inclusive = false. This
ensures the transaction at recovery_target_lsn is not reapplied during
recovery, avoiding duplication when replication begins.

Bug #18897
Reported-by: Zane Duffield <duffieldzane@gmail.com>
Author: Shlok Kyal <shlok.kyal.oss@gmail.com>
Reviewed-by: vignesh C <vignesh21@gmail.com>
Reviewed-by: Amit Kapila <amit.kapila16@gmail.com>
Backpatch-through: 17, where it was introduced
Discussion: https://postgr.es/m/18897-d3db67535860dddb@postgresql.org
This commit is contained in:
Amit Kapila
2025-07-24 08:36:31 +00:00
parent 635a856279
commit 967309116f
1 changed files with 10 additions and 1 deletions
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11
src/bin/pg_basebackup/pg_createsubscriber.c
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@@ -1206,8 +1206,17 @@ setup_recovery(const struct LogicalRepInfo *dbinfo, const char *datadir, const c
appendPQExpBuffer(recoveryconfcontents, "recovery_target = ''\n");
appendPQExpBuffer(recoveryconfcontents,
"recovery_target_timeline = 'latest'\n");
/*
* Set recovery_target_inclusive = false to avoid reapplying the
* transaction committed at 'lsn' after subscription is enabled. This is
* because the provided 'lsn' is also used as the replication start point
* for the subscription. So, the server can send the transaction committed
* at that 'lsn' after replication is started which can lead to applying
* the same transaction twice if we keep recovery_target_inclusive = true.
*/
appendPQExpBuffer(recoveryconfcontents,
"recovery_target_inclusive = true\n");
"recovery_target_inclusive = false\n");
appendPQExpBuffer(recoveryconfcontents,
"recovery_target_action = promote\n");
appendPQExpBuffer(recoveryconfcontents, "recovery_target_name = ''\n");