Fix user mapping object description

We were using "user mapping for user XYZ" as description for user mappings, but
that's ambiguous because users can have mappings on multiple foreign
servers; therefore change it to "for user XYZ on server UVW" instead.
Object identities for user mappings are also updated in the same way, in
branches 9.3 and above.

The incomplete description string was introduced together with the whole
SQL/MED infrastructure by commit cae565e of 8.4 era, so backpatch all
the way back.

Author: alvherre

src/backend/catalog/objectaddress.c

@@ -2510,14 +2510,17 @@ getObjectDescription(const ObjectAddress *object)
 				HeapTuple	tup;
 				Oid			useid;
 				char	   *usename;
+				Form_pg_user_mapping umform;
+				ForeignServer *srv;
 
 				tup = SearchSysCache1(USERMAPPINGOID,
 									  ObjectIdGetDatum(object->objectId));
 				if (!HeapTupleIsValid(tup))
 					elog(ERROR, "cache lookup failed for user mapping %u",
 						 object->objectId);
-
-				useid = ((Form_pg_user_mapping) GETSTRUCT(tup))->umuser;
+				umform = (Form_pg_user_mapping) GETSTRUCT(tup);
+				useid = umform->umuser;
+				srv = GetForeignServer(umform->umserver);
 
 				ReleaseSysCache(tup);
 
@@ -2526,7 +2529,8 @@ getObjectDescription(const ObjectAddress *object)
 				else
 					usename = "public";
 
-				appendStringInfo(&buffer, _("user mapping for %s"), usename);
+				appendStringInfo(&buffer, _("user mapping for %s on server %s"), usename,
+								 srv->servername);
 				break;
 			}
 
@@ -3906,19 +3910,18 @@ getObjectIdentityParts(const ObjectAddress *object,
 			{
 				HeapTuple	tup;
 				Oid			useid;
+				Form_pg_user_mapping umform;
+				ForeignServer *srv;
 				const char *usename;
 
-				/* no objname support */
-				if (objname)
-					*objname = NIL;
-
 				tup = SearchSysCache1(USERMAPPINGOID,
 									  ObjectIdGetDatum(object->objectId));
 				if (!HeapTupleIsValid(tup))
 					elog(ERROR, "cache lookup failed for user mapping %u",
 						 object->objectId);
-
-				useid = ((Form_pg_user_mapping) GETSTRUCT(tup))->umuser;
+				umform = (Form_pg_user_mapping) GETSTRUCT(tup);
+				useid = umform->umuser;
+				srv = GetForeignServer(umform->umserver);
 
 				ReleaseSysCache(tup);
 
@@ -3927,7 +3930,14 @@ getObjectIdentityParts(const ObjectAddress *object,
 				else
 					usename = "public";
 
-				appendStringInfoString(&buffer, usename);
+				if (objname)
+				{
+					*objname = list_make1(pstrdup(usename));
+					*objargs = list_make1(pstrdup(srv->servername));
+				}
+
+				appendStringInfo(&buffer, "%s on server %s", usename,
+								 srv->servername);
 				break;
 			}
 

src/test/regress/expected/foreign_data.out

@@ -247,7 +247,7 @@ CREATE USER MAPPING FOR current_user SERVER s1;
 DROP FOREIGN DATA WRAPPER foo;                              -- ERROR
 ERROR:  cannot drop foreign-data wrapper foo because other objects depend on it
 DETAIL:  server s1 depends on foreign-data wrapper foo
-user mapping for foreign_data_user depends on server s1
+user mapping for foreign_data_user on server s1 depends on server s1
 HINT:  Use DROP ... CASCADE to drop the dependent objects too.
 SET ROLE regress_test_role;
 DROP FOREIGN DATA WRAPPER foo CASCADE;                      -- ERROR
@@ -256,7 +256,7 @@ RESET ROLE;
 DROP FOREIGN DATA WRAPPER foo CASCADE;
 NOTICE:  drop cascades to 2 other objects
 DETAIL:  drop cascades to server s1
-drop cascades to user mapping for foreign_data_user
+drop cascades to user mapping for foreign_data_user on server s1
 \dew+
                                             List of foreign-data wrappers
     Name    |       Owner       | Handler |        Validator         | Access privileges | FDW Options | Description 
@@ -526,10 +526,10 @@ CREATE USER MAPPING FOR current_user SERVER s3;
 
 DROP SERVER s3;                                             -- ERROR
 ERROR:  cannot drop server s3 because other objects depend on it
-DETAIL:  user mapping for foreign_data_user depends on server s3
+DETAIL:  user mapping for foreign_data_user on server s3 depends on server s3
 HINT:  Use DROP ... CASCADE to drop the dependent objects too.
 DROP SERVER s3 CASCADE;
-NOTICE:  drop cascades to user mapping for foreign_data_user
+NOTICE:  drop cascades to user mapping for foreign_data_user on server s3
 \des
              List of foreign servers
  Name |       Owner       | Foreign-data wrapper 
@@ -1183,8 +1183,8 @@ GRANT USAGE ON FOREIGN SERVER s9 TO regress_test_role;
 CREATE USER MAPPING FOR current_user SERVER s9;
 DROP SERVER s9 CASCADE;
 NOTICE:  drop cascades to 2 other objects
-DETAIL:  drop cascades to user mapping for public
-drop cascades to user mapping for unprivileged_role
+DETAIL:  drop cascades to user mapping for public on server s9
+drop cascades to user mapping for unprivileged_role on server s9
 RESET ROLE;
 CREATE SERVER s9 FOREIGN DATA WRAPPER foo;
 GRANT USAGE ON FOREIGN SERVER s9 TO unprivileged_role;
@@ -1256,14 +1256,14 @@ DROP ROLE regress_test_role;                                -- ERROR
 ERROR:  role "regress_test_role" cannot be dropped because some objects depend on it
 DETAIL:  privileges for server s4
 privileges for foreign-data wrapper foo
-owner of user mapping for regress_test_role
-owner of user mapping for regress_test_role
+owner of user mapping for regress_test_role on server s6
+owner of user mapping for regress_test_role on server s5
 owner of server s5
 owner of server t2
 DROP SERVER s5 CASCADE;
-NOTICE:  drop cascades to user mapping for regress_test_role
+NOTICE:  drop cascades to user mapping for regress_test_role on server s5
 DROP SERVER t1 CASCADE;
-NOTICE:  drop cascades to user mapping for public
+NOTICE:  drop cascades to user mapping for public on server t1
 DROP SERVER t2;
 DROP USER MAPPING FOR regress_test_role SERVER s6;
 -- This test causes some order dependent cascade detail output,
@@ -1274,8 +1274,8 @@ NOTICE:  drop cascades to 5 other objects
 \set VERBOSITY default
 DROP SERVER s8 CASCADE;
 NOTICE:  drop cascades to 2 other objects
-DETAIL:  drop cascades to user mapping for foreign_data_user
-drop cascades to user mapping for public
+DETAIL:  drop cascades to user mapping for foreign_data_user on server s8
+drop cascades to user mapping for public on server s8
 DROP ROLE regress_test_indirect;
 DROP ROLE regress_test_role;
 DROP ROLE unprivileged_role;                                -- ERROR