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-- predictability
SET synchronous_commit = on;
SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot_stats', 'test_decoding');
CREATE TABLE stats_test(data text);
-- function to wait for counters to advance
CREATE FUNCTION wait_for_decode_stats(check_reset bool, check_spill_txns bool) RETURNS void AS $$
DECLARE
start_time timestamptz := clock_timestamp();
updated bool;
BEGIN
-- we don't want to wait forever; loop will exit after 30 seconds
FOR i IN 1 .. 300 LOOP
IF check_spill_txns THEN
-- check to see if all updates have been reset/updated
SELECT CASE WHEN check_reset THEN (spill_txns = 0)
ELSE (spill_txns > 0)
END
INTO updated
FROM pg_stat_replication_slots WHERE slot_name='regression_slot_stats';
ELSE
-- check to see if all updates have been reset/updated
SELECT CASE WHEN check_reset THEN (total_txns = 0)
ELSE (total_txns > 0)
END
INTO updated
FROM pg_stat_replication_slots WHERE slot_name='regression_slot_stats';
END IF;
exit WHEN updated;
-- wait a little
perform pg_sleep_for('100 milliseconds');
-- reset stats snapshot so we can test again
perform pg_stat_clear_snapshot();
END LOOP;
-- report time waited in postmaster log (where it won't change test output)
RAISE LOG 'wait_for_decode_stats delayed % seconds',
extract(epoch from clock_timestamp() - start_time);
END
$$ LANGUAGE plpgsql;
-- non-spilled xact
SET logical_decoding_work_mem to '64MB';
INSERT INTO stats_test values(1);
SELECT count(*) FROM pg_logical_slot_get_changes('regression_slot_stats', 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 logical_decoding_work_mem;
-- reset the slot stats, and wait for stats collector's total txn to reset
SELECT pg_stat_reset_replication_slot('regression_slot_stats');
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);
COMMIT;
SELECT count(*) FROM pg_logical_slot_peek_changes('regression_slot_stats', NULL, NULL, 'skip-empty-xacts', '1');
-- 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 slot_name, spill_txns > 0 AS spill_txns, spill_count > 0 AS spill_count 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;
SELECT slot_name FROM pg_stat_replication_slots;
SELECT slot_name FROM pg_stat_replication_slots;
COMMIT;
DROP FUNCTION wait_for_decode_stats(bool, bool);
DROP TABLE stats_test;
SELECT pg_drop_replication_slot('regression_slot_stats');
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