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5db6a344ab
Commit 76b78721ca introduced two new columns in pg_stat_replication_slots
to improve monitoring of slot synchronization. One of these columns was
named slotsync_skip_at, which is inconsistent with the naming convention
used for similar columns in other system views.
Columns that store timestamps of the most recent event typically use the
'last_' in the column name (e.g., last_autovacuum, checksum_last_failure).
Renaming slotsync_skip_at to slotsync_last_skip aligns with this pattern,
making the purpose of the column clearer and improving overall consistency
across the views.
Author: Shlok Kyal <shlok.kyal.oss@gmail.com>
Reviewed-by: Michael Banck <mbanck@gmx.net>
Discussion: https://postgr.es/m/20251128091552.GB13635@p46.dedyn.io;lightning.p46.dedyn.io
Discussion: https://postgr.es/m/CAE9k0PkhfKrTEAsGz4DjOhEj1nQ+hbQVfvWUxNacD38ibW3a1g@mail.gmail.com
187 lines
8.6 KiB
Plaintext
187 lines
8.6 KiB
Plaintext
-- predictability
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SET synchronous_commit = on;
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SELECT 'init' FROM
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pg_create_logical_replication_slot('regression_slot_stats1', 'test_decoding') s1,
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pg_create_logical_replication_slot('regression_slot_stats2', 'test_decoding') s2,
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pg_create_logical_replication_slot('regression_slot_stats3', 'test_decoding') s3;
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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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-- non-spilled xact
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SET logical_decoding_work_mem to '64MB';
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INSERT INTO stats_test values(1);
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SELECT count(*) FROM pg_logical_slot_get_changes('regression_slot_stats1', NULL, NULL, 'skip-empty-xacts', '1');
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count
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-------
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3
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(1 row)
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SELECT count(*) FROM pg_logical_slot_get_changes('regression_slot_stats2', NULL, NULL, 'skip-empty-xacts', '1');
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count
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-------
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3
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(1 row)
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SELECT count(*) FROM pg_logical_slot_get_changes('regression_slot_stats3', NULL, NULL, 'skip-empty-xacts', '1');
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count
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-------
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3
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(1 row)
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SELECT pg_stat_force_next_flush();
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pg_stat_force_next_flush
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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, total_txns > 0 AS total_txns, total_bytes > 0 AS total_bytes, mem_exceeded_count = 0 AS mem_exceeded_count FROM pg_stat_replication_slots ORDER BY slot_name;
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slot_name | spill_txns | spill_count | total_txns | total_bytes | mem_exceeded_count
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------------------------+------------+-------------+------------+-------------+--------------------
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regression_slot_stats1 | t | t | t | t | t
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regression_slot_stats2 | t | t | t | t | t
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regression_slot_stats3 | t | t | t | t | t
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(3 rows)
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RESET logical_decoding_work_mem;
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-- reset stats for one slot, others should be unaffected
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SELECT pg_stat_reset_replication_slot('regression_slot_stats1');
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pg_stat_reset_replication_slot
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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, total_txns > 0 AS total_txns, total_bytes > 0 AS total_bytes, mem_exceeded_count = 0 AS mem_exceeded_count FROM pg_stat_replication_slots ORDER BY slot_name;
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slot_name | spill_txns | spill_count | total_txns | total_bytes | mem_exceeded_count
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------------------------+------------+-------------+------------+-------------+--------------------
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regression_slot_stats1 | t | t | f | f | t
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regression_slot_stats2 | t | t | t | t | t
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regression_slot_stats3 | t | t | t | t | t
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(3 rows)
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-- reset stats for all slots
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SELECT pg_stat_reset_replication_slot(NULL);
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pg_stat_reset_replication_slot
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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, total_txns > 0 AS total_txns, total_bytes > 0 AS total_bytes, mem_exceeded_count = 0 AS mem_exceeded_count FROM pg_stat_replication_slots ORDER BY slot_name;
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slot_name | spill_txns | spill_count | total_txns | total_bytes | mem_exceeded_count
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------------------------+------------+-------------+------------+-------------+--------------------
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regression_slot_stats1 | t | t | f | f | t
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regression_slot_stats2 | t | t | f | f | t
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regression_slot_stats3 | t | t | f | f | t
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(3 rows)
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-- verify accessing/resetting stats for non-existent slot does something reasonable
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SELECT * FROM pg_stat_get_replication_slot('do-not-exist');
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slot_name | spill_txns | spill_count | spill_bytes | stream_txns | stream_count | stream_bytes | mem_exceeded_count | total_txns | total_bytes | slotsync_skip_count | slotsync_last_skip | stats_reset
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--------------+------------+-------------+-------------+-------------+--------------+--------------+--------------------+------------+-------------+---------------------+--------------------+-------------
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do-not-exist | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | |
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(1 row)
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SELECT pg_stat_reset_replication_slot('do-not-exist');
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ERROR: replication slot "do-not-exist" does not exist
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SELECT * FROM pg_stat_get_replication_slot('do-not-exist');
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slot_name | spill_txns | spill_count | spill_bytes | stream_txns | stream_count | stream_bytes | mem_exceeded_count | total_txns | total_bytes | slotsync_skip_count | slotsync_last_skip | stats_reset
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--------------+------------+-------------+-------------+-------------+--------------+--------------+--------------------+------------+-------------+---------------------+--------------------+-------------
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do-not-exist | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | |
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(1 row)
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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_stats1', 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. We can't test the exact stats count as that can vary if any
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-- background transaction (say by autovacuum) happens in parallel to the main
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-- transaction.
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SELECT pg_stat_force_next_flush();
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pg_stat_force_next_flush
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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, mem_exceeded_count > 0 AS mem_exceeded_count FROM pg_stat_replication_slots;
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slot_name | spill_txns | spill_count | mem_exceeded_count
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------------------------+------------+-------------+--------------------
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regression_slot_stats1 | t | t | t
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regression_slot_stats2 | f | f | f
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regression_slot_stats3 | f | f | f
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(3 rows)
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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_stats1
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regression_slot_stats2
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regression_slot_stats3
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(3 rows)
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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_stats1
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regression_slot_stats2
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regression_slot_stats3
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(3 rows)
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COMMIT;
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SELECT 'init' FROM pg_create_logical_replication_slot('regression_slot_stats4_twophase', 'test_decoding', false, true) s4;
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?column?
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----------
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init
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(1 row)
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-- The INSERT changes are large enough to be spilled but will not be, because
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-- the transaction is aborted. The logical decoding skips collecting further
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-- changes too. The transaction is prepared to make sure the decoding processes
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-- the aborted transaction.
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BEGIN;
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INSERT INTO stats_test SELECT 'serialize-toobig--1:'||g.i FROM generate_series(1, 5000) g(i);
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PREPARE TRANSACTION 'test1_abort';
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ROLLBACK PREPARED 'test1_abort';
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SELECT count(*) FROM pg_logical_slot_get_changes('regression_slot_stats4_twophase', NULL, NULL, 'include-xids', '0', 'skip-empty-xacts', '1');
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count
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-------
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1
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(1 row)
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-- Verify that the decoding doesn't spill already-aborted transaction's changes.
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-- Given that there is no concurrent activities that are capturable by logical decoding,
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-- mem_exceeded_count should theoretically be 1 but we check if >0 here since it's
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-- more flexible for potential future changes and adequate for the testing purpose.
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SELECT pg_stat_force_next_flush();
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pg_stat_force_next_flush
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--------------------------
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(1 row)
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SELECT slot_name, spill_txns, spill_count, mem_exceeded_count > 0 as mem_exceeded_count FROM pg_stat_replication_slots WHERE slot_name = 'regression_slot_stats4_twophase';
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slot_name | spill_txns | spill_count | mem_exceeded_count
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---------------------------------+------------+-------------+--------------------
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regression_slot_stats4_twophase | 0 | 0 | t
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(1 row)
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DROP TABLE stats_test;
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SELECT pg_drop_replication_slot('regression_slot_stats1'),
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pg_drop_replication_slot('regression_slot_stats2'),
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pg_drop_replication_slot('regression_slot_stats3'),
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pg_drop_replication_slot('regression_slot_stats4_twophase');
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pg_drop_replication_slot | pg_drop_replication_slot | pg_drop_replication_slot | pg_drop_replication_slot
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--------------------------+--------------------------+--------------------------+--------------------------
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(1 row)
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