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Libing Song
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BUG#25379659 MASTER MAY BINLOG A WRONG LAST_COMMITED
DESCRIPTION =========== Transactions could binlog a last_commited smaller than expected. With the wrong last_commited values, the transactions which sould be applied sequentially could be applied parallel. That caused applier errors or data inconsistency. ANALYSIS ======== When committing a transaction, its last_commited is set to the value of max_committed_transaction. max_committed_transaction is the maximum sequence_number of committed transactions. It is maintained just before committing each transaction to engine. If its sequence_number is not SEQ_UNINIT then updates max_committed_transaction accordingly. However, it checked wrong sequence_number(the sequence_number of the leader thread's transaction instead of the sequence_number of the transaction). That caused that max_committed_transaction was only updated in time for leader thread's transaction. The update for following transactions were delay to finish_commit() which was after the transaction commited to engine. FIX === Just checks its own sequence_number of each transaction instead of the sequence_number of the leader thransaction.
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‎mysql-test/include/assert_logical_timestamps.inc‎

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@@ -45,7 +45,7 @@ if ($binlog_position)
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# Check for match.
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--let $assert_select= last_committed=.*sequence_number=.*
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--let $assert_match= `SELECT CONCAT('^[^\n]*last_committed=', REPLACE(REPLACE('$logical_timestamps', ';', '.*\n[^\n]*last_committed='), ' ', '\tsequence_number='))`
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--let $assert_match= `SELECT CONCAT('last_committed=', REPLACE(REPLACE('$logical_timestamps', ';', '.*\n[^\n]*last_committed='), ' ', '\tsequence_number='))`
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--let $assert_text= assert_logical_timestamps: $logical_timestamps
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--let $extra_debug_info= Expected logical timestamps: $logical_timestamps
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--source include/assert_grep.inc

‎mysql-test/suite/binlog/r/binlog_wrong_last_committed.result‎

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RESET MASTER;
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CREATE TABLE t1(c1 INT PRIMARY KEY, c2 INT) ENGINE = InnoDB;
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SET DEBUG_SYNC = "bgc_after_enrolling_for_commit_stage
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SIGNAL insert1_ready WAIT_FOR continue_commit_stage";
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INSERT INTO t1 VALUES(1, 1);
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SET DEBUG_SYNC = "now WAIT_FOR insert1_ready";
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SET DEBUG_SYNC = "reached_finish_commit WAIT_FOR insert2_finish";
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INSERT INTO t1 VALUES(2, 1);
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SET DEBUG_SYNC = "now SIGNAL continue_commit_stage";
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UPDATE t1 SET c2 = 2 WHERE c1 = 2;
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SET DEBUG_SYNC = "now SIGNAL insert2_finish";
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include/include/assert_logical_timestamps.inc [3 4]
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DROP TABLE t1;

‎mysql-test/suite/binlog/t/binlog_wrong_last_committed.test‎

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################################################################################
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# BUG#25379659 MASTER MAY BINLOG A WRONG LAST_COMMITED
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#
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# Transactions could binlog a last_commited smaller than expected. With the
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# wrong last_commited values, the transactions which sould be applied
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# sequentially could be applied parallel. That caused applier errors or data
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# inconsistency.
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#
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# When committing a transaction, its last_commited is set to the value of
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# max_committed_transaction. max_committed_transaction is the maximum
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# sequence_number of committed transactions. It is maintained just before
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# committing each transaction to engine. If its sequence_number is not
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# SEQ_UNINIT then updates max_committed_transaction accordingly.
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#
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# However, it checked wrong sequence_number(the sequence_number of the
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# leader thread's transaction instead of the sequence_number of the transaction).
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# That caused that max_committed_transaction was only updated in time for leader
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# thread's transaction. The update for following transactions were delay to
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# finish_commit() which was after the transaction commited to engine.
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#
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# The test verifys last_committed is corret in the bug situation.
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#
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# Step 1. Use debug sync to gurantee that commit queue has two transactions.
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# Step 2. Use debug sync to pause the second transaction when it enters
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# finshi_commit()
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# Step 3. Execute a transaction and check if its last_committed is correct.
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################################################################################
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--source include/have_binlog_format_statement.inc
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--source include/have_debug_sync.inc
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# Reset sequence_number and last_committed, so we can check the exact number
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# Make sure it starts from master-bin.000001
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RESET MASTER;
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CREATE TABLE t1(c1 INT PRIMARY KEY, c2 INT) ENGINE = InnoDB;
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# Make the INSERT to wait for another INSERT into the flush queue
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SET DEBUG_SYNC = "bgc_after_enrolling_for_commit_stage
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SIGNAL insert1_ready WAIT_FOR continue_commit_stage";
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--send INSERT INTO t1 VALUES(1, 1)
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--connect(conn1, localhost, root)
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--connect(conn2, localhost, root)
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--connection conn1
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# Make sure above INSERT is the leader
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SET DEBUG_SYNC = "now WAIT_FOR insert1_ready";
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# Record the INSERT's binlog position
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--let $binlog_pos= query_get_value(SHOW MASTER STATUS, Position, 1)
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# Pause the INSERT when it enters finishi_commit()
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SET DEBUG_SYNC = "reached_finish_commit WAIT_FOR insert2_finish";
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--send INSERT INTO t1 VALUES(2, 1)
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# Wait until above INSERT is binlogged
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--connection conn2
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--let $show_statement= SHOW MASTER STATUS
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--let $field= Position
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--let $condition= != '$binlog_pos'
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--source include/wait_show_condition.inc
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# Signal insert1 to finish the commit group
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SET DEBUG_SYNC = "now SIGNAL continue_commit_stage";
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--connection default
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--reap
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UPDATE t1 SET c2 = 2 WHERE c1 = 2;
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SET DEBUG_SYNC = "now SIGNAL insert2_finish";
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--connection conn1
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--reap
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--connection default
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# INSERT(2,1): sequence_number = 3
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# UPDATE: sequence_number = 4, last_committed = 3
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--let $binlog_file= master-bin.000001
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--let $logical_timestamps= 3 4
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--source include/assert_logical_timestamps.inc
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DROP TABLE t1;

‎sql/binlog.cc‎

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@@ -8644,7 +8644,7 @@ MYSQL_BIN_LOG::process_commit_stage_queue(THD *thd, THD *first)
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#ifndef DBUG_OFF
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stage_manager.clear_preempt_status(head);
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#endif
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if (thd->get_transaction()->sequence_number != SEQ_UNINIT)
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if (head->get_transaction()->sequence_number != SEQ_UNINIT)
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update_max_committed(head);
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/*
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Flush/Sync error should be ignored and continue

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