doc: Add note that DROP SUBSCRIPTION drops replication slot

Add some information about what to do when this fails.

diff --git a/doc/src/sgml/ref/drop_subscription.sgml b/doc/src/sgml/ref/drop_subscription.sgml
index 4f34a35eefe680d8fd07d1a42bb69ab34119f49f..42068d617bcafd08c5fc13104838b1c289649fd2 100644 (file)
--- a/doc/src/sgml/ref/drop_subscription.sgml
+++ b/doc/src/sgml/ref/drop_subscription.sgml
@@ -73,6 +73,28 @@ DROP SUBSCRIPTION [ IF EXISTS ] name
   
  
 
+ 
+  Notes
+
+  
+   When dropping a subscription that is associated with a replication slot on
+   the remote host (the normal state), DROP SUBSCRIPTION
+   will connect to the remote host and try to drop the replication slot as
+   part of its operation.  This is necessary so that the resources allocated
+   for the subscription on the remote host are released.  If this fails,
+   either because the remote host is not reachable or because the remote
+   replication slot cannot be dropped or does not exist or never existed,
+   the DROP SUBSCRIPTION command will fail.  To proceed in
+   this situation, disassociate the subscription from the replication slot by
+   executing ALTER SUBSCRIPTION ... SET (slot_name = NONE).
+   After that, DROP SUBSCRIPTION will no longer attempt any
+   actions on a remote host.  Note that if the remote replication slot still
+   exists, it should then be dropped manually; otherwise it will continue to
+   reserve WAL and might eventually cause the disk to fill up.  See
+   also .
+  
+ 
+
  
   Examples