diff options
| author | Amit Kapila <akapila@postgresql.org> | 2025-05-19 11:28:19 +0530 |
|---|---|---|
| committer | Amit Kapila <akapila@postgresql.org> | 2025-05-19 11:28:19 +0530 |
| commit | 9d1a6235960697b5dbc5e0b7d56d59c0a6de3b3d (patch) | |
| tree | cd5b35e157b75178161809236853f235c2b491ac /src | |
| parent | 00652b3c9fb7bf2122bb076d63b15bc65e12ff71 (diff) | |
Don't retreat slot's confirmed_flush LSN.
Prevent moving the confirmed_flush backwards, as this could lead to data
duplication issues caused by replicating already replicated changes.
This can happen when a client acknowledges an LSN it doesn't have to do
anything for, and thus didn't store persistently. After a restart, the
client can send the prior LSN that it stored persistently as an
acknowledgement, but we need to ignore such an LSN to avoid retreating
confirm_flush LSN.
Diagnosed-by: Zhijie Hou <houzj.fnst@fujitsu.com>
Author: shveta malik <shveta.malik@gmail.com>
Reviewed-by: Amit Kapila <amit.kapila16@gmail.com>
Reviewed-by: Dilip Kumar <dilipbalaut@gmail.com>
Tested-by: Nisha Moond <nisha.moond412@gmail.com>
Backpatch-through: 13
Discussion: https://postgr.es/m/CAJpy0uDZ29P=BYB1JDWMCh-6wXaNqMwG1u1mB4=10Ly0x7HhwQ@mail.gmail.com
Discussion: https://postgr.es/m/OS0PR01MB57164AB5716AF2E477D53F6F9489A@OS0PR01MB5716.jpnprd01.prod.outlook.com
Diffstat (limited to 'src')
| -rw-r--r-- | src/backend/replication/logical/logical.c | 23 |
1 files changed, 21 insertions, 2 deletions
diff --git a/src/backend/replication/logical/logical.c b/src/backend/replication/logical/logical.c index a53d42e88a6..74e22fff78d 100644 --- a/src/backend/replication/logical/logical.c +++ b/src/backend/replication/logical/logical.c @@ -1753,7 +1753,19 @@ LogicalConfirmReceivedLocation(XLogRecPtr lsn) SpinLockAcquire(&MyReplicationSlot->mutex); - MyReplicationSlot->data.confirmed_flush = lsn; + /* + * Prevent moving the confirmed_flush backwards, as this could lead to + * data duplication issues caused by replicating already replicated + * changes. + * + * This can happen when a client acknowledges an LSN it doesn't have + * to do anything for, and thus didn't store persistently. After a + * restart, the client can send the prior LSN that it stored + * persistently as an acknowledgement, but we need to ignore such an + * LSN. See similar case handling in CreateDecodingContext. + */ + if (lsn > MyReplicationSlot->data.confirmed_flush) + MyReplicationSlot->data.confirmed_flush = lsn; /* if we're past the location required for bumping xmin, do so */ if (MyReplicationSlot->candidate_xmin_lsn != InvalidXLogRecPtr && @@ -1818,7 +1830,14 @@ LogicalConfirmReceivedLocation(XLogRecPtr lsn) else { SpinLockAcquire(&MyReplicationSlot->mutex); - MyReplicationSlot->data.confirmed_flush = lsn; + + /* + * Prevent moving the confirmed_flush backwards. See comments above + * for the details. + */ + if (lsn > MyReplicationSlot->data.confirmed_flush) + MyReplicationSlot->data.confirmed_flush = lsn; + SpinLockRelease(&MyReplicationSlot->mutex); } } |