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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
18 lines
557 B
Text
18 lines
557 B
Text
--- instant_alter_purge.result
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+++ instant_alter_purge,release.result
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@@ -32,15 +32,10 @@
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START TRANSACTION WITH CONSISTENT SNAPSHOT;
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connection default;
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DELETE FROM t1;
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-SET DEBUG_SYNC='innodb_commit_inplace_alter_table_enter SIGNAL go WAIT_FOR do';
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ALTER TABLE t1 ADD COLUMN f3 INT;
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connection purge_control;
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-SET DEBUG_SYNC='now WAIT_FOR go';
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COMMIT;
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SET GLOBAL innodb_max_purge_lag_wait= 0;
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-InnoDB 0 transactions not purged
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-SET DEBUG_SYNC='now SIGNAL do';
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disconnect purge_control;
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connection default;
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-SET DEBUG_SYNC=RESET;
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DROP TABLE t1;
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