Fix some comments related to logical repslot advancing

confirmed_flush is part of a replication slot's information, but not
confirmed_lsn.

Author: Kyotaro Horiguchi
Discussion: https://postgr.es/m/20191226.175919.17237335658671970.horikyota.ntt@gmail.com
Backpatch-through: 11

diff --git a/src/backend/replication/slotfuncs.c b/src/backend/replication/slotfuncs.c
index 6683fc3f9b749bc226866cf26c280847414a99f0..ba08ad405f463e116e794518782cd0bb6afd6bc7 100644 (file)
--- a/src/backend/replication/slotfuncs.c
+++ b/src/backend/replication/slotfuncs.c
@@ -378,8 +378,8 @@ pg_physical_replication_slot_advance(XLogRecPtr moveto)
 /*
  * Helper function for advancing our logical replication slot forward.
  *
- * The slot's restart_lsn is used as start point for reading records,
- * while confirmed_lsn is used as base point for the decoding context.
+ * The slot's restart_lsn is used as start point for reading records, while
+ * confirmed_flush is used as base point for the decoding context.
  *
  * We cannot just do LogicalConfirmReceivedLocation to update confirmed_flush,
  * because we need to digest WAL to advance restart_lsn allowing to recycle
@@ -549,8 +549,8 @@ pg_replication_slot_advance(PG_FUNCTION_ARGS)
    /*
     * Check if the slot is not moving backwards.  Physical slots rely simply
     * on restart_lsn as a minimum point, while logical slots have confirmed
-    * consumption up to confirmed_lsn, meaning that in both cases data older
-    * than that is not available anymore.
+    * consumption up to confirmed_flush, meaning that in both cases data
+    * older than that is not available anymore.
     */
    if (OidIsValid(MyReplicationSlot->data.database))
        minlsn = MyReplicationSlot->data.confirmed_flush;