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MDEV-40995 Fix AUTO_INCREMENT race condition in partitioned tables #5627

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MDEV-40995 Fix AUTO_INCREMENT race condition in partitioned tables #5627

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MDEV-40995 concurrent INSERT ... SELECT on a partitioned InnoDB table…
greypilgrim-083 Sep 4, 2026
282a343
Update test to properly test MDEV-40995
greypilgrim-083 Sep 28, 2026
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28 changes: 28 additions & 0 deletions mysql-test/suite/parts/r/mdev_40995.result
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Original file line number Diff line number Diff line change
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#
# MDEV-40995 concurrent INSERT ... SELECT on a partitioned InnoDB table
# can leave the table-level AUTO_INCREMENT counter behind MAX(pk)
#
CREATE TABLE t1 (
id INT AUTO_INCREMENT,
pk2 INT NOT NULL,
a INT,
PRIMARY KEY (id, pk2),
UNIQUE KEY (a, pk2)
) ENGINE=InnoDB PARTITION BY HASH(pk2) PARTITIONS 2;
INSERT INTO t1 (pk2, a) VALUES (1, 10), (1, 100), (1, 110);
connect con1,localhost,root,,;
connect con2,localhost,root,,;
connection con1;
SET DEBUG_SYNC = 'ha_partition_get_auto_increment_after_reservation SIGNAL start_t2 WAIT_FOR t2_done EXECUTE 1';
INSERT INTO t1 (pk2, a) SELECT pk2, a+10 FROM t1 WHERE pk2=1 ORDER BY a;;
connection con2;
SET DEBUG_SYNC = 'now WAIT_FOR start_t2';
INSERT INTO t1 (pk2, a) VALUES (2, 200);
SET DEBUG_SYNC = 'now SIGNAL t2_done';
connection con1;
ERROR 23000: Duplicate entry '110-1' for key 'a'
connection default;
INSERT INTO t1 (pk2, a) VALUES (2, 300);
INSERT INTO t1 (pk2, a) VALUES (2, 400);
DROP TABLE t1;
SET DEBUG_SYNC = 'RESET';
1 change: 1 addition & 0 deletions mysql-test/suite/parts/t/mdev_40995-master.opt
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--innodb-autoinc-lock-mode=2
41 changes: 41 additions & 0 deletions mysql-test/suite/parts/t/mdev_40995.test
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--source include/have_debug_sync.inc
--source include/have_partition.inc
--source include/have_innodb.inc

--echo #
--echo # MDEV-40995 concurrent INSERT ... SELECT on a partitioned InnoDB table
--echo # can leave the table-level AUTO_INCREMENT counter behind MAX(pk)
--echo #

CREATE TABLE t1 (
id INT AUTO_INCREMENT,
pk2 INT NOT NULL,
a INT,
PRIMARY KEY (id, pk2),
UNIQUE KEY (a, pk2)
) ENGINE=InnoDB PARTITION BY HASH(pk2) PARTITIONS 2;

INSERT INTO t1 (pk2, a) VALUES (1, 10), (1, 100), (1, 110);

--connect (con1,localhost,root,,)
--connect (con2,localhost,root,,)

--connection con1
SET DEBUG_SYNC = 'ha_partition_get_auto_increment_after_reservation SIGNAL start_t2 WAIT_FOR t2_done EXECUTE 1';
--send INSERT INTO t1 (pk2, a) SELECT pk2, a+10 FROM t1 WHERE pk2=1 ORDER BY a;

--connection con2
SET DEBUG_SYNC = 'now WAIT_FOR start_t2';
INSERT INTO t1 (pk2, a) VALUES (2, 200);
SET DEBUG_SYNC = 'now SIGNAL t2_done';

--connection con1
--error ER_DUP_ENTRY
--reap

--connection default
INSERT INTO t1 (pk2, a) VALUES (2, 300);
INSERT INTO t1 (pk2, a) VALUES (2, 400);

DROP TABLE t1;
SET DEBUG_SYNC = 'RESET';
4 changes: 3 additions & 1 deletion sql/ha_partition.cc
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Expand Up @@ -11107,6 +11107,7 @@ void ha_partition::get_auto_increment(ulonglong offset, ulonglong increment,
part_share->next_auto_inc_val+= nb_desired_values * increment;

unlock_auto_increment();
DEBUG_SYNC(ha_thd(), "ha_partition_get_auto_increment_after_reservation");
DBUG_PRINT("info", ("*first_value: %lu", (ulong) *first_value));
*nb_reserved_values= nb_desired_values;
}
Expand Down Expand Up @@ -11139,7 +11140,8 @@ void ha_partition::release_auto_increment()
we can lower the reserved value.
*/
if (next_insert_id < next_auto_inc_val &&
auto_inc_interval_for_cur_row.maximum() >= next_auto_inc_val)
auto_inc_interval_for_cur_row.maximum() >= next_auto_inc_val &&
next_insert_id >= auto_inc_interval_for_cur_row.minimum())
{
THD *thd= ha_thd();
/*
Expand Down