Various temporary slots test improvements

Fix the tests on slow machines (per buildfarm).

Add test for dropping on error.  And also try to consume real changes
from temporary slots.

From: Petr Jelinek <petr.jelinek@2ndquadrant.com>

contrib/test_decoding/expected/slot.out

@@ -22,19 +22,27 @@ SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot_p', 'test
  init
 (1 row)
 
+SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot_t2', 'test_decoding', true);
+ ?column? 
+----------
+ init
+(1 row)
+
 -- here we want to start a new session and wait till old one is gone
 select pg_backend_pid() as oldpid \gset
 \c -
 do 'declare c int = 0;
 begin
-  while (select count(*) from pg_stat_activity where pid = '
+  while (select count(*) from pg_replication_slots where active_pid = '
     :'oldpid'
-  ') > 0 loop c := c + 1; perform pg_stat_clear_snapshot(); end loop;
+  ') > 0 loop c := c + 1; perform pg_sleep(0.01); end loop;
   raise log ''slot test looped % times'', c;
 end';
--- should fail because the temporary slot was dropped automatically
+-- should fail because the temporary slots were dropped automatically
 SELECT pg_drop_replication_slot('regression_slot_t');
 ERROR:  replication slot "regression_slot_t" does not exist
+SELECT pg_drop_replication_slot('regression_slot_t2');
+ERROR:  replication slot "regression_slot_t2" does not exist
 -- permanent slot has survived
 SELECT pg_drop_replication_slot('regression_slot_p');
  pg_drop_replication_slot 
@@ -49,19 +57,44 @@ SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot1', 'test_
  init
 (1 row)
 
+CREATE TABLE replication_example(id SERIAL PRIMARY KEY, somedata int, text varchar(120));
+BEGIN;
+INSERT INTO replication_example(somedata, text) VALUES (1, 1);
+INSERT INTO replication_example(somedata, text) VALUES (1, 2);
+COMMIT;
 SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot2', 'test_decoding', true);
  ?column? 
 ----------
  init
 (1 row)
 
-SELECT * FROM pg_logical_slot_get_changes('regression_slot1', NULL, NULL);
- location | xid | data 
-----------+-----+------
-(0 rows)
+INSERT INTO replication_example(somedata, text) VALUES (1, 3);
+SELECT data FROM pg_logical_slot_get_changes('regression_slot1', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
+                                                  data                                                   
+---------------------------------------------------------------------------------------------------------
+ BEGIN
+ table public.replication_example: INSERT: id[integer]:1 somedata[integer]:1 text[character varying]:'1'
+ table public.replication_example: INSERT: id[integer]:2 somedata[integer]:1 text[character varying]:'2'
+ COMMIT
+ BEGIN
+ table public.replication_example: INSERT: id[integer]:3 somedata[integer]:1 text[character varying]:'3'
+ COMMIT
+(7 rows)
 
-SELECT * FROM pg_logical_slot_get_changes('regression_slot2', NULL, NULL);
- location | xid | data 
-----------+-----+------
-(0 rows)
+SELECT data FROM pg_logical_slot_get_changes('regression_slot2', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
+                                                  data                                                   
+---------------------------------------------------------------------------------------------------------
+ BEGIN
+ table public.replication_example: INSERT: id[integer]:3 somedata[integer]:1 text[character varying]:'3'
+ COMMIT
+(3 rows)
 
+DROP TABLE replication_example;
+-- error
+SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot1', 'test_decoding', true);
+ERROR:  replication slot "regression_slot1" already exists
+-- both should error as they should be dropped on error
+SELECT pg_drop_replication_slot('regression_slot1');
+ERROR:  replication slot "regression_slot1" does not exist
+SELECT pg_drop_replication_slot('regression_slot2');
+ERROR:  replication slot "regression_slot2" does not exist

contrib/test_decoding/sql/slot.sql

@@ -4,25 +4,47 @@ SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot_t', 'test
 SELECT pg_drop_replication_slot('regression_slot_p');
 SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot_p', 'test_decoding', false);
 
+SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot_t2', 'test_decoding', true);
+
 -- here we want to start a new session and wait till old one is gone
 select pg_backend_pid() as oldpid \gset
 \c -
 do 'declare c int = 0;
 begin
-  while (select count(*) from pg_stat_activity where pid = '
+  while (select count(*) from pg_replication_slots where active_pid = '
     :'oldpid'
-  ') > 0 loop c := c + 1; perform pg_stat_clear_snapshot(); end loop;
+  ') > 0 loop c := c + 1; perform pg_sleep(0.01); end loop;
   raise log ''slot test looped % times'', c;
 end';
 
--- should fail because the temporary slot was dropped automatically
+-- should fail because the temporary slots were dropped automatically
 SELECT pg_drop_replication_slot('regression_slot_t');
+SELECT pg_drop_replication_slot('regression_slot_t2');
 
 -- permanent slot has survived
 SELECT pg_drop_replication_slot('regression_slot_p');
 
 -- test switching between slots in a session
 SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot1', 'test_decoding', true);
+
+CREATE TABLE replication_example(id SERIAL PRIMARY KEY, somedata int, text varchar(120));
+BEGIN;
+INSERT INTO replication_example(somedata, text) VALUES (1, 1);
+INSERT INTO replication_example(somedata, text) VALUES (1, 2);
+COMMIT;
+
 SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot2', 'test_decoding', true);
-SELECT * FROM pg_logical_slot_get_changes('regression_slot1', NULL, NULL);
-SELECT * FROM pg_logical_slot_get_changes('regression_slot2', NULL, NULL);
+
+INSERT INTO replication_example(somedata, text) VALUES (1, 3);
+
+SELECT data FROM pg_logical_slot_get_changes('regression_slot1', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
+SELECT data FROM pg_logical_slot_get_changes('regression_slot2', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
+
+DROP TABLE replication_example;
+
+-- error
+SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot1', 'test_decoding', true);
+
+-- both should error as they should be dropped on error
+SELECT pg_drop_replication_slot('regression_slot1');
+SELECT pg_drop_replication_slot('regression_slot2');