Details
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Bug
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Status: Open (View Workflow)
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Major
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Resolution: Unresolved
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10.6.10
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None
Description
Current documentation https://mariadb.com/kb/en/innodb-lock-modes/#intention-locks :
Gap locks are disabled if ... the isolation level is set to READ COMMITTED.
I am pretty sure all connections below use READ-COMMITTED and no binlogging enabled - still observe several times per day deadlocks because of ` gap before rec insert intention waiting` while inserting rows into a small table:
LATEST DETECTED DEADLOCK
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------------------------
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2023-04-06 07:59:31 0x7f8d4bed3700
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*** (1) TRANSACTION:
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TRANSACTION 6942075065, ACTIVE 0 sec inserting
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mysql tables in use 1, locked 1
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LOCK WAIT 3 lock struct(s), heap size 1128, 4 row lock(s), undo log entries 1
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MariaDB thread id 6036630, OS thread handle 140244840953600, query id 1967907196 192.168.xx.xx mirrorcache Update
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insert into mojo_pubsub_subscribe (pid, channel) values ('6036637', 'minion.job') on duplicate key update ts=current_timestamp
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*** WAITING FOR THIS LOCK TO BE GRANTED:
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RECORD LOCKS space id 31 page no 4 n bits 648 index subs_idx of table `mirrorcache`.`mojo_pubsub_subscribe` trx id 6942075065 lock_mode X locks gap before rec insert intention waiting
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Record lock, heap no 237 PHYSICAL RECORD: n_fields 3; compact format; info bits 32
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0: len 4; hex 805c1ce0; asc \ ;;
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1: len 10; hex 6d696e696f6e2e6a6f62; asc minion.job;;
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2: len 4; hex 886f6a12; asc oj ;;
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*** CONFLICTING WITH:
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RECORD LOCKS space id 31 page no 4 n bits 648 index subs_idx of table `mirrorcache`.`mojo_pubsub_subscribe` trx id 6942075065 lock_mode X
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Record lock, heap no 237 PHYSICAL RECORD: n_fields 3; compact format; info bits 32
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0: len 4; hex 805c1ce0; asc \ ;;
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1: len 10; hex 6d696e696f6e2e6a6f62; asc minion.job;;
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2: len 4; hex 886f6a12; asc oj ;;
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Record lock, heap no 313 PHYSICAL RECORD: n_fields 3; compact format; info bits 32
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0: len 4; hex 805c1c9d; asc \ ;;
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1: len 10; hex 6d696e696f6e2e6a6f62; asc minion.job;;
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2: len 4; hex 886f692d; asc oi-;;
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Record lock, heap no 591 PHYSICAL RECORD: n_fields 3; compact format; info bits 32
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0: len 4; hex 805c1c9d; asc \ ;;
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1: len 10; hex 6d696e696f6e2e6a6f62; asc minion.job;;
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2: len 4; hex 886f6a40; asc oj@;;
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*** (2) TRANSACTION:
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TRANSACTION 6942075066, ACTIVE 0 sec inserting
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mysql tables in use 1, locked 1
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LOCK WAIT 2 lock struct(s), heap size 1128, 1 row lock(s), undo log entries 1
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MariaDB thread id 6036732, OS thread handle 140245429069568, query id 1967907198 192.168.xx.yy mirrorcache Update
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insert into mojo_pubsub_subscribe (pid, channel) values ('6036704', 'minion.job') on duplicate key update ts=current_timestamp
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*** WAITING FOR THIS LOCK TO BE GRANTED:
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RECORD LOCKS space id 31 page no 4 n bits 648 index subs_idx of table `mirrorcache`.`mojo_pubsub_subscribe` trx id 6942075066 lock_mode X waiting
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Record lock, heap no 237 PHYSICAL RECORD: n_fields 3; compact format; info bits 32
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0: len 4; hex 805c1ce0; asc \ ;;
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1: len 10; hex 6d696e696f6e2e6a6f62; asc minion.job;;
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2: len 4; hex 886f6a12; asc oj ;;
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*** CONFLICTING WITH:
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RECORD LOCKS space id 31 page no 4 n bits 648 index subs_idx of table `mirrorcache`.`mojo_pubsub_subscribe` trx id 6942075065 lock_mode X
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Record lock, heap no 237 PHYSICAL RECORD: n_fields 3; compact format; info bits 32
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0: len 4; hex 805c1ce0; asc \ ;;
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1: len 10; hex 6d696e696f6e2e6a6f62; asc minion.job;;
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2: len 4; hex 886f6a12; asc oj ;;
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Record lock, heap no 313 PHYSICAL RECORD: n_fields 3; compact format; info bits 32
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0: len 4; hex 805c1c9d; asc \ ;;
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1: len 10; hex 6d696e696f6e2e6a6f62; asc minion.job;;
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2: len 4; hex 886f692d; asc oi-;;
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Record lock, heap no 591 PHYSICAL RECORD: n_fields 3; compact format; info bits 32
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0: len 4; hex 805c1c9d; asc \ ;;
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1: len 10; hex 6d696e696f6e2e6a6f62; asc minion.job;;
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2: len 4; hex 886f6a40; asc oj@;;
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*** WE ROLL BACK TRANSACTION (2)
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Table structure:
https://github.com/jhthorsen/mojo-mysql/blob/a558cb6e6316b270cf61d0d394a8a4a0b556928b/lib/Mojo/mysql/PubSub.pm#L276
MariaDB [mirrorcache]> show global variables like 'tx_i%';
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+---------------+----------------+
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| Variable_name | Value |
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+---------------+----------------+
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| tx_isolation | READ-COMMITTED |
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+---------------+----------------+
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1 row in set (0.001 sec)
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MariaDB [mirrorcache]> select version();
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+-----------------+
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| version() |
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+-----------------+
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| 10.6.10-MariaDB |
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+-----------------+
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1 row in set (0.000 sec)
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