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Add information of total data processed to replication slot stats.

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This adds the statistics about total transactions count and total
transaction data logically sent to the decoding output plugin from
ReorderBuffer. Users can query the pg_stat_replication_slots view to check
these stats.

Suggested-by: Andres Freund
Author: Vignesh C and Amit Kapila
Reviewed-by: Sawada Masahiko, Amit Kapila
Discussion: https://postgr.es/m/20210319185247.ldebgpdaxsowiflw@alap3.anarazel.de
This commit is contained in:
Amit Kapila
2021-04-16 07:34:43 +05:30
parent 1bf946bd43
commit f5fc2f5b23
15 changed files with 256 additions and 52 deletions
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79
contrib/test_decoding/expected/stats.out
View File

@ -8,7 +8,7 @@ SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_d
CREATE TABLE stats_test(data text);
-- function to wait for counters to advance
CREATE FUNCTION wait_for_decode_stats(check_reset bool) RETURNS void AS $$
CREATE FUNCTION wait_for_decode_stats(check_reset bool, check_spill_txns bool) RETURNS void AS $$
DECLARE
start_time timestamptz := clock_timestamp();
updated bool;
@ -16,12 +16,25 @@ BEGIN
-- we don't want to wait forever; loop will exit after 30 seconds
FOR i IN 1 .. 300 LOOP
-- check to see if all updates have been reset/updated
SELECT CASE WHEN check_reset THEN (spill_txns = 0)
ELSE (spill_txns > 0)
END
INTO updated
FROM pg_stat_replication_slots WHERE slot_name='regression_slot';
IF check_spill_txns THEN
-- check to see if all updates have been reset/updated
SELECT CASE WHEN check_reset THEN (spill_txns = 0)
ELSE (spill_txns > 0)
END
INTO updated
FROM pg_stat_replication_slots WHERE slot_name='regression_slot';
ELSE
-- check to see if all updates have been reset/updated
SELECT CASE WHEN check_reset THEN (total_txns = 0)
ELSE (total_txns > 0)
END
INTO updated
FROM pg_stat_replication_slots WHERE slot_name='regression_slot';
END IF;
exit WHEN updated;
@ -51,16 +64,16 @@ SELECT count(*) FROM pg_logical_slot_peek_changes('regression_slot', NULL, NULL,
-- 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);
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 FROM pg_stat_replication_slots;
slot_name | spill_txns | spill_count
-----------------+------------+-------------
regression_slot | t | t
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
@ -70,16 +83,16 @@ SELECT pg_stat_reset_replication_slot('regression_slot');
(1 row)
SELECT wait_for_decode_stats(true);
SELECT wait_for_decode_stats(true, true);
wait_for_decode_stats
-----------------------
(1 row)
SELECT slot_name, spill_txns, spill_count FROM pg_stat_replication_slots;
slot_name | spill_txns | spill_count
-----------------+------------+-------------
regression_slot | 0 | 0
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 | 0 | 0 | 0 | 0
(1 row)
-- decode and check stats again.
@ -89,16 +102,36 @@ SELECT count(*) FROM pg_logical_slot_peek_changes('regression_slot', NULL, NULL,
5002
(1 row)
SELECT wait_for_decode_stats(false);
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 FROM pg_stat_replication_slots;
slot_name | spill_txns | spill_count
-----------------+------------+-------------
regression_slot | t | t
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)
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);
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 | f | f | t | t
(1 row)
-- Ensure stats can be repeatedly accessed using the same stats snapshot. See
@ -117,7 +150,7 @@ SELECT slot_name FROM pg_stat_replication_slots;
(1 row)
COMMIT;
DROP FUNCTION wait_for_decode_stats(bool);
DROP FUNCTION wait_for_decode_stats(bool, bool);
DROP TABLE stats_test;
SELECT pg_drop_replication_slot('regression_slot');
pg_drop_replication_slot