Anyone see why tx_isolation=REPEATABLE-READ should have a next-record lock on record 3 rather than a record lock? SESSION 1: MariaDB [drupal_test]> create table x ( x bigint unsigned not null auto_increment, PRIMARY KEY x) ); Query OK, 0 rows affected (0.02 sec) MariaDB [drupal_test]> select @@tx_isolation; +-----------------+ | @@tx_isolation | +-----------------+ | REPEATABLE-READ | +-----------------+ 1 row in set (0.00 sec) MariaDB [drupal_test]> insert into x values (1),(2),(3); Query OK, 3 rows affected (0.00 sec) Records: 3 Duplicates: 0 Warnings: 0 MariaDB [drupal_test]> begin -> ; Query OK, 0 rows affected (0.00 sec) MariaDB [drupal_test]> delete from x where x <= 3; Query OK, 3 rows affected (0.00 sec) ---TRANSACTION 290E30, ACTIVE 12 sec 2 lock struct(s), heap size 376, 4 row lock(s), undo log entries 3 MySQL thread id 7437, OS thread handle 0x7f37307f5700, query id 3298653 localhost debian-sys-maint sleeping TABLE LOCK table `drupal_test`.`x` trx id 290E30 lock mode IX RECORD LOCKS space id 82547 page no 3 n bits 72 index `PRIMARY` of table `drupal_test`.`x` trx id 290E30 lock_mode X SESSION 2: MariaDB [drupal_test]> insert into x values (DEFAULT); ERROR 1205 (HY000): Lock wait timeout exceeded; try restarting transaction And it works in READ-COMMITTED SESSION 1: MariaDB [drupal_test]> set tx_isolation='READ-COMMITTED'; begin; delete from x where x <= 3; Query OK, 0 rows affected (0.00 sec) Query OK, 0 rows affected (0.00 sec) Query OK, 3 rows affected (0.00 sec) SESSION 2: ---TRANSACTION 290E33, ACTIVE 44 sec 2 lock struct(s), heap size 376, 3 row lock(s), undo log entries 3 MySQL thread id 7437, OS thread handle 0x7f37307f5700, query id 3298661 localhost debian-sys-maint sleeping TABLE LOCK table `drupal_test`.`x` trx id 290E33 lock mode IX RECORD LOCKS space id 82547 page no 3 n bits 72 index `PRIMARY` of table `drupal_test`.`x` trx id 290E33 lock_mode X locks rec but not gap MariaDB [drupal_test]> insert into x values (DEFAULT); Query OK, 1 row affected (0.00 sec) -- -- Daniel Black, Engineer @ Open Query (http://openquery.com.au) Remote expertise & maintenance for MySQL/MariaDB server environments.