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How does Postgres detect deadlock?
Postgres detects deadlock If the two transactions are each inserting multiple rows into the table, transaction a may attempt to insert a key previously inserted by transaction b . This causes transaction a to attempt to acquire a lock on transaction b . Now b is waiting on a and a is waiting on b . Deadlock!
How does Postgres deal with deadlock?
When Postgres Blocks: 7 Tips for Dealing With Locks
- Never Add a Column With a Default Value.
- Beware of Lock Queues; Use Lock Timeouts.
- Create Indexes Concurrently.
- Take Aggressive Locks as Late as Possible.
- Adding a Primary Key With Minimal Locking.
- Avoid Deadlocks by Ordering Commands.
Why does PostgreSQL wait for deadlock timeout?
The reason is that transactions have to wait for one another. If two transactions are in a conflict, PostgreSQL will not resolve the problem immediately, rather it will wait for deadlock_timeout and then trigger the deadlock detection algorithm to resolve the problem. Why does PostgreSQL wait for some time before it steps in and fixes things?
When to use deadlock timeout in lock management?
Lock Management deadlock_timeout (integer) This is the amount of time, in milliseconds, to wait on a lock before checking to see if there is a deadlock condition. […] When log_lock_waits is set, this parameter also determines the length of time to wait before a log message is issued about the lock wait.
Which is the best defense against deadlocks in PostgreSQL?
The best defense against deadlocks is generally to avoid them by being certain that all applications using a database acquire locks on multiple objects in a consistent order. The deadlock timeout is the amount of time that PostgreSQL waits on a lock before it checks for a deadlock.
Where do I find deadlock timeout in lmgr?
The deadlock_timeout case is handled in backend/storage/lmgr/proc.c , while the 40P01/ERRCODE_T_R_DEADLOCK_DETECTED case in backend/storage/lmgr/deadlock.c Are these actually two different types of deadlocks that are detected? Is there a way to get an error when deadlock_timeout based deadlock detection happens?