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14685b10df
The motivation of introducing the parameter innodb_purge_rseg_truncate_frequency in mysql/mysql-server@28bbd66ea5 and mysql/mysql-server@8fc2120fed seems to have been to avoid stalls due to freeing undo log pages or truncating undo log tablespaces. In MariaDB Server, innodb_undo_log_truncate=ON should be a much lighter operation than in MySQL, because it will not involve any log checkpoint. Another source of performance stalls should be trx_purge_truncate_rseg_history(), which is shrinking the history list by freeing the undo log pages whose undo records have been purged. To alleviate that, we will introduce a purge_truncation_task that will offload this from the purge_coordinator_task. In that way, the next innodb_purge_batch_size pages may be parsed and purged while the pages from the previous batch are being freed and the history list being shrunk. The processing of innodb_undo_log_truncate=ON will still remain the responsibility of the purge_coordinator_task. purge_coordinator_state::count: Remove. We will ignore innodb_purge_rseg_truncate_frequency, and act as if it had been set to 1 (the maximum shrinking frequency). purge_coordinator_state::do_purge(): Invoke an asynchronous task purge_truncation_callback() to free the undo log pages. purge_sys_t::iterator::free_history(): Free those undo log pages that have been processed. This used to be a part of trx_purge_truncate_history(). purge_sys_t::clone_end_view(): Take a new value of purge_sys.head as a parameter, so that it will be updated while holding exclusive purge_sys.latch. This is needed for race-free access to the field in purge_truncation_callback(). Reviewed by: Vladislav Lesin
87 lines
1.9 KiB
Text
87 lines
1.9 KiB
Text
#
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# Bug #84958 InnoDB's MVCC has O(N^2) behaviors
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# https://bugs.mysql.com/bug.php?id=84958
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#
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# Set up the test with a procedure and a function.
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#
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CREATE PROCEDURE insert_n(start int, end int)
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BEGIN
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DECLARE i INT DEFAULT start;
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WHILE i <= end do
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INSERT INTO t1 VALUES (1, 2, 3) ON DUPLICATE KEY UPDATE c = i;
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SET i = i + 1;
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END WHILE;
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END~~
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CREATE FUNCTION num_pages_get()
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RETURNS INT
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BEGIN
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DECLARE ret INT;
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SELECT variable_value INTO ret
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FROM information_schema.global_status
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WHERE variable_name = 'innodb_buffer_pool_read_requests';
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RETURN ret;
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END~~
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#
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# Create a table with one record in it and start an RR transaction
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#
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CREATE TABLE t1 (a INT, b INT, c INT, PRIMARY KEY(a,b), KEY (b,c))
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ENGINE=InnoDB STATS_PERSISTENT=0;
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InnoDB 0 transactions not purged
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BEGIN;
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SELECT * FROM t1;
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a b c
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#
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# Create 100 newer record versions in con2 and con3
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#
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connect con2, localhost, root,,;
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connection con2;
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BEGIN;
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INSERT INTO t1 VALUES (1, 2, 3) ON DUPLICATE KEY UPDATE c = NULL;
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CALL insert_n(1, 50);;
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connect con3, localhost, root,,;
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connection con3;
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BEGIN;
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CALL insert_n(51, 100);;
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connection con2;
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COMMIT;
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connection con3;
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INSERT INTO t1 VALUES (1, 2, 1) ON DUPLICATE KEY UPDATE c = NULL;
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COMMIT;
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connection default;
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#
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# Connect to default and record how many pages were accessed
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# when selecting the record using the secondary key.
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#
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InnoDB 2 transactions not purged
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SET @num_pages_1 = num_pages_get();
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SELECT * FROM t1 force index (b);
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a b c
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SET @num_pages_2= num_pages_get();
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SELECT IF(@num_pages_2 - @num_pages_1 < 5000, 'OK', @num_pages_2 - @num_pages_1) num_pages_diff;
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num_pages_diff
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OK
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#
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# Commit and show the final record.
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#
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SELECT * FROM t1;
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a b c
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SELECT * FROM t1 force index (b);
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a b c
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COMMIT;
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SELECT * FROM t1 force index (b);
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a b c
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1 2 NULL
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SELECT * FROM t1;
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a b c
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1 2 NULL
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CHECK TABLE t1;
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Table Op Msg_type Msg_text
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test.t1 check status OK
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#
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# Cleanup
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#
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disconnect con2;
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disconnect con3;
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DROP TABLE t1;
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DROP PROCEDURE insert_n;
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DROP FUNCTION num_pages_get;
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