Why default value of rocksdb_deadlock_detect option is FALSE?

[brew74]

According to the MyRocks storage engine variables of Percona server for MySQL
([URL=“MyRocks Server Variables — Percona Server 5.7 Documentation”]https://www.percona.com/doc/percona-...eadlock_detect[/URL]), rocksdb_deadlock_detect variables’ default value is FALSE.

Does this mean there’s no deadlock checks in RocksDB engine ?
And we should rely on rocksdb_lock_wait_timeout ?

Is there any reason deadlock check is disabled on RocksDB ?

Thanks in advance.

[George_Lorch]

This is/was a decision originally made by Facebook developers and we simply inherited it without much consideration. I believe the original decision is based on their performance requirements. This deadlock detection would start traversing locks and transactions as soon as a locker was refused a lock where otherwise the locker would just go into a lock-wait (i.e. a record that the locker wants to lock is already locked by something else). In many cases, there is no real deadlock, just a lock wait. This extra searching for a deadlock where there likely isn’t one creates a potential performance hit. In general, I believe it is meant to be a troubleshooting tool after lock wait timeouts are experienced possibly due to deadlocking, not to prevent them.