pgstat: drop subscription stats regardless of slot, fix comment

There's no reason anymore to only drop subscription stats if associated with a
slot, now that stats drops are transactional. Additionally, the comment
referring to autovacuum cleaning up stats was clearly outdated.

Author: Masahiko Sawada <sawada.mshk@gmail.com>
Discussion: https://postgr.es/m/CAD21AoAwiby3HeJE7vJe16Gr75RFfJ640dyHqvsiUhyKJTXPtw@mail.gmail.com
Backpatch: 15-

diff --git a/src/backend/commands/subscriptioncmds.c b/src/backend/commands/subscriptioncmds.c
index 83e6eae855f9891026cc12979e87ee426a1f933b..3842a4fd445be7e225809e567636ceaedfe25d6b 100644 (file)
--- a/src/backend/commands/subscriptioncmds.c
+++ b/src/backend/commands/subscriptioncmds.c
@@ -1579,15 +1579,9 @@ DropSubscription(DropSubscriptionStmt *stmt, bool isTopLevel)
 
        /*
         * Tell the cumulative stats system that the subscription is getting
-        * dropped. We can safely report dropping the subscription statistics here
-        * if the subscription is associated with a replication slot since we
-        * cannot run DROP SUBSCRIPTION inside a transaction block.  Subscription
-        * statistics will be removed later by (auto)vacuum either if it's not
-        * associated with a replication slot or if the message for dropping the
-        * subscription gets lost.
+        * dropped.
         */
-       if (slotname)
-               pgstat_drop_subscription(subid);
+       pgstat_drop_subscription(subid);
 
        table_close(rel, NoLock);
 }