Fix test case added by commit f5fc2f5b23.

In the new test after resetting the stats, we were not waiting for the
stats message to be delivered. Also, we need to decode the results for
the new test, otherwise, it will show the old stats.

In passing,
a. Change docs added by commit f5fc2f5b23 as per suggestion by
Justin Pryzby.
b. Bump the PGSTAT_FILE_FORMAT_ID as commit f5fc2f5b23 changes the file
format of stats.

Reported-by: Tom Lane based on buildfarm reports
Author: Vignesh C, Justin Pryzby
Reviewed-by: Amit Kapila
Discussion: https://postgr.es/m/20210319185247.ldebgpdaxsowiflw@alap3.anarazel.de

2 files changed, 49 insertions, 26 deletions

diff --git a/contrib/test_decoding/expected/stats.out b/contrib/test_decoding/expected/stats.out
index bc8e601eab..86d594ca15 100644
--- a/contrib/test_decoding/expected/stats.out
+++ b/contrib/test_decoding/expected/stats.out
@@ -51,39 +51,34 @@ BEGIN
     extract(epoch from clock_timestamp() - start_time);
 END
 $$ LANGUAGE plpgsql;
--- spilling the xact
-BEGIN;
-INSERT INTO stats_test SELECT 'serialize-topbig--1:'||g.i FROM generate_series(1, 5000) g(i);
-COMMIT;
-SELECT count(*) FROM pg_logical_slot_peek_changes('regression_slot', NULL, NULL, 'skip-empty-xacts', '1');
+-- non-spilled xact
+INSERT INTO stats_test values(1);
+SELECT count(*) FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'skip-empty-xacts', '1');
  count 
 -------
-  5002
+     3
 (1 row)
 
--- Check stats, wait for the stats collector to update. We can't test the
--- exact stats count as that can vary if any background transaction (say by
--- autovacuum) happens in parallel to the main transaction.
-SELECT wait_for_decode_stats(false, true);
+SELECT wait_for_decode_stats(false, false);
  wait_for_decode_stats 
 -----------------------
  
 (1 row)
 
-SELECT slot_name, spill_txns > 0 AS spill_txns, spill_count > 0 AS spill_count, total_txns > 0 AS total_txns, total_bytes > 0 AS total_bytes FROM pg_stat_replication_slots;
+SELECT slot_name, spill_txns = 0 AS spill_txns, spill_count = 0 AS spill_count, total_txns > 0 AS total_txns, total_bytes > 0 AS total_bytes FROM pg_stat_replication_slots;
     slot_name    | spill_txns | spill_count | total_txns | total_bytes 
 -----------------+------------+-------------+------------+-------------
  regression_slot | t          | t           | t          | t
 (1 row)
 
--- reset the slot stats, and wait for stats collector to reset
+-- reset the slot stats, and wait for stats collector's total txn to reset
 SELECT pg_stat_reset_replication_slot('regression_slot');
  pg_stat_reset_replication_slot 
 --------------------------------
  
 (1 row)
 
-SELECT wait_for_decode_stats(true, true);
+SELECT wait_for_decode_stats(true, false);
  wait_for_decode_stats 
 -----------------------
  
@@ -95,13 +90,19 @@ SELECT slot_name, spill_txns, spill_count, total_txns, total_bytes FROM pg_stat_
  regression_slot |          0 |           0 |          0 |           0
 (1 row)
 
--- decode and check stats again.
+-- spilling the xact
+BEGIN;
+INSERT INTO stats_test SELECT 'serialize-topbig--1:'||g.i FROM generate_series(1, 5000) g(i);
+COMMIT;
 SELECT count(*) FROM pg_logical_slot_peek_changes('regression_slot', NULL, NULL, 'skip-empty-xacts', '1');
  count 
 -------
   5002
 (1 row)
 
+-- Check stats, wait for the stats collector to update. We can't test the
+-- exact stats count as that can vary if any background transaction (say by
+-- autovacuum) happens in parallel to the main transaction.
 SELECT wait_for_decode_stats(false, true);
  wait_for_decode_stats 
 -----------------------
@@ -114,24 +115,42 @@ SELECT slot_name, spill_txns > 0 AS spill_txns, spill_count > 0 AS spill_count,
  regression_slot | t          | t           | t          | t
 (1 row)
 
+-- reset the slot stats, and wait for stats collector to reset
 SELECT pg_stat_reset_replication_slot('regression_slot');
  pg_stat_reset_replication_slot 
 --------------------------------
  
 (1 row)
 
--- non-spilled xact
-INSERT INTO stats_test values(generate_series(1, 10));
-SELECT wait_for_decode_stats(false, false);
+SELECT wait_for_decode_stats(true, true);
  wait_for_decode_stats 
 -----------------------
  
 (1 row)
 
-SELECT slot_name, spill_txns = 0 AS spill_txns, spill_count = 0 AS spill_count, total_txns > 0 AS total_txns, total_bytes > 0 AS total_bytes FROM pg_stat_replication_slots;
+SELECT slot_name, spill_txns, spill_count, total_txns, total_bytes FROM pg_stat_replication_slots;
     slot_name    | spill_txns | spill_count | total_txns | total_bytes 
 -----------------+------------+-------------+------------+-------------
- regression_slot | f          | f           | t          | t
+ regression_slot |          0 |           0 |          0 |           0
+(1 row)
+
+-- decode and check stats again.
+SELECT count(*) FROM pg_logical_slot_peek_changes('regression_slot', NULL, NULL, 'skip-empty-xacts', '1');
+ count 
+-------
+  5002
+(1 row)
+
+SELECT wait_for_decode_stats(false, true);
+ wait_for_decode_stats 
+-----------------------
+ 
+(1 row)
+
+SELECT slot_name, spill_txns > 0 AS spill_txns, spill_count > 0 AS spill_count, total_txns > 0 AS total_txns, total_bytes > 0 AS total_bytes FROM pg_stat_replication_slots;
+    slot_name    | spill_txns | spill_count | total_txns | total_bytes 
+-----------------+------------+-------------+------------+-------------
+ regression_slot | t          | t           | t          | t
 (1 row)
 
 -- Ensure stats can be repeatedly accessed using the same stats snapshot. See
diff --git a/contrib/test_decoding/sql/stats.sql b/contrib/test_decoding/sql/stats.sql
index 8c34aeced1..03fc27e537 100644
--- a/contrib/test_decoding/sql/stats.sql
+++ b/contrib/test_decoding/sql/stats.sql
@@ -50,6 +50,17 @@ BEGIN
 END
 $$ LANGUAGE plpgsql;
 
+-- non-spilled xact
+INSERT INTO stats_test values(1);
+SELECT count(*) FROM pg_logical_slot_get_changes('regression_slot', NULL, NULL, 'skip-empty-xacts', '1');
+SELECT wait_for_decode_stats(false, false);
+SELECT slot_name, spill_txns = 0 AS spill_txns, spill_count = 0 AS spill_count, total_txns > 0 AS total_txns, total_bytes > 0 AS total_bytes FROM pg_stat_replication_slots;
+
+-- reset the slot stats, and wait for stats collector's total txn to reset
+SELECT pg_stat_reset_replication_slot('regression_slot');
+SELECT wait_for_decode_stats(true, false);
+SELECT slot_name, spill_txns, spill_count, total_txns, total_bytes FROM pg_stat_replication_slots;
+
 -- spilling the xact
 BEGIN;
 INSERT INTO stats_test SELECT 'serialize-topbig--1:'||g.i FROM generate_series(1, 5000) g(i);
@@ -72,13 +83,6 @@ SELECT count(*) FROM pg_logical_slot_peek_changes('regression_slot', NULL, NULL,
 SELECT wait_for_decode_stats(false, true);
 SELECT slot_name, spill_txns > 0 AS spill_txns, spill_count > 0 AS spill_count, total_txns > 0 AS total_txns, total_bytes > 0 AS total_bytes FROM pg_stat_replication_slots;
 
-SELECT pg_stat_reset_replication_slot('regression_slot');
-
--- non-spilled xact
-INSERT INTO stats_test values(generate_series(1, 10));
-SELECT wait_for_decode_stats(false, false);
-SELECT slot_name, spill_txns = 0 AS spill_txns, spill_count = 0 AS spill_count, total_txns > 0 AS total_txns, total_bytes > 0 AS total_bytes FROM pg_stat_replication_slots;
-
 -- Ensure stats can be repeatedly accessed using the same stats snapshot. See
 -- https://postgr.es/m/20210317230447.c7uc4g3vbs4wi32i%40alap3.anarazel.de
 BEGIN;