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5f79580ad6
When accessing replication slot stats, introduced in 9868167500,
pgstat_read_statsfiles() reads the data into newly allocated
memory. Unfortunately the current memory context at that point is the
callers, leading to leaks and use-after-free dangers.
The fix is trivial, explicitly use pgStatLocalContext. There's some
potential for further improvements, but that's outside of the scope of
this bugfix.
No backpatch necessary, feature is only in HEAD.
Author: Andres Freund <andres@anarazel.de>
Discussion: https://postgr.es/m/20210317230447.c7uc4g3vbs4wi32i@alap3.anarazel.de
128 lines
3.5 KiB
Plaintext
128 lines
3.5 KiB
Plaintext
-- predictability
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SET synchronous_commit = on;
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SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot', 'test_decoding');
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?column?
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----------
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init
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(1 row)
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CREATE TABLE stats_test(data text);
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-- function to wait for counters to advance
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CREATE FUNCTION wait_for_decode_stats(check_reset bool) RETURNS void AS $$
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DECLARE
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start_time timestamptz := clock_timestamp();
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updated bool;
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BEGIN
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-- we don't want to wait forever; loop will exit after 30 seconds
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FOR i IN 1 .. 300 LOOP
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-- check to see if all updates have been reset/updated
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SELECT CASE WHEN check_reset THEN (spill_txns = 0)
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ELSE (spill_txns > 0)
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END
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INTO updated
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FROM pg_stat_replication_slots WHERE slot_name='regression_slot';
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exit WHEN updated;
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-- wait a little
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perform pg_sleep_for('100 milliseconds');
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-- reset stats snapshot so we can test again
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perform pg_stat_clear_snapshot();
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END LOOP;
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-- report time waited in postmaster log (where it won't change test output)
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RAISE LOG 'wait_for_decode_stats delayed % seconds',
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extract(epoch from clock_timestamp() - start_time);
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END
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$$ LANGUAGE plpgsql;
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-- spilling the xact
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BEGIN;
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INSERT INTO stats_test SELECT 'serialize-topbig--1:'||g.i FROM generate_series(1, 5000) g(i);
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COMMIT;
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SELECT count(*) FROM pg_logical_slot_peek_changes('regression_slot', NULL, NULL, 'skip-empty-xacts', '1');
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count
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-------
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5002
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(1 row)
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-- Check stats, wait for the stats collector to update. We can't test the
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-- exact stats count as that can vary if any background transaction (say by
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-- autovacuum) happens in parallel to the main transaction.
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SELECT wait_for_decode_stats(false);
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wait_for_decode_stats
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-----------------------
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(1 row)
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SELECT slot_name, spill_txns > 0 AS spill_txns, spill_count > 0 AS spill_count FROM pg_stat_replication_slots;
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slot_name | spill_txns | spill_count
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-----------------+------------+-------------
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regression_slot | t | t
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(1 row)
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-- reset the slot stats, and wait for stats collector to reset
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SELECT pg_stat_reset_replication_slot('regression_slot');
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pg_stat_reset_replication_slot
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--------------------------------
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(1 row)
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SELECT wait_for_decode_stats(true);
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wait_for_decode_stats
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-----------------------
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(1 row)
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SELECT slot_name, spill_txns, spill_count FROM pg_stat_replication_slots;
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slot_name | spill_txns | spill_count
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-----------------+------------+-------------
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regression_slot | 0 | 0
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(1 row)
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-- decode and check stats again.
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SELECT count(*) FROM pg_logical_slot_peek_changes('regression_slot', NULL, NULL, 'skip-empty-xacts', '1');
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count
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-------
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5002
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(1 row)
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SELECT wait_for_decode_stats(false);
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wait_for_decode_stats
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-----------------------
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(1 row)
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SELECT slot_name, spill_txns > 0 AS spill_txns, spill_count > 0 AS spill_count FROM pg_stat_replication_slots;
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slot_name | spill_txns | spill_count
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-----------------+------------+-------------
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regression_slot | t | t
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(1 row)
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-- Ensure stats can be repeatedly accessed using the same stats snapshot. See
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-- https://postgr.es/m/20210317230447.c7uc4g3vbs4wi32i%40alap3.anarazel.de
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BEGIN;
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SELECT slot_name FROM pg_stat_replication_slots;
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slot_name
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-----------------
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regression_slot
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(1 row)
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SELECT slot_name FROM pg_stat_replication_slots;
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slot_name
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-----------------
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regression_slot
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(1 row)
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COMMIT;
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DROP FUNCTION wait_for_decode_stats(bool);
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DROP TABLE stats_test;
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SELECT pg_drop_replication_slot('regression_slot');
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pg_drop_replication_slot
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--------------------------
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(1 row)
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