Add confirmed_flush column to pg_replication_slots.

There's no reason not to expose both restart_lsn and confirmed_flush
since they have rather distinct meanings. The former is the oldest WAL
still required and valid for both physical and logical slots, whereas
the latter is the location up to which a logical slot's consumer has
confirmed receiving data. Most of the time a slot will require older
WAL (i.e. restart_lsn) than the confirmed
position (i.e. confirmed_flush_lsn).

Author: Marko Tiikkaja, editorialized by me
Discussion: 559D110B.1020109@joh.to

1 files changed, 2 insertions, 1 deletions

diff --git a/src/backend/catalog/system_views.sql b/src/backend/catalog/system_views.sql
index c0bd6fa96b..3190c7f7e0 100644
--- a/src/backend/catalog/system_views.sql
+++ b/src/backend/catalog/system_views.sql
@@ -676,7 +676,8 @@ CREATE VIEW pg_replication_slots AS
             L.active_pid,
             L.xmin,
             L.catalog_xmin,
-            L.restart_lsn
+            L.restart_lsn,
+            L.confirmed_flush_lsn
     FROM pg_get_replication_slots() AS L
             LEFT JOIN pg_database D ON (L.datoid = D.oid);