Contents
Why are there so many locks in PostgreSQL?
To make sure complex transactions can safely run at the same time, PostgreSQL uses several layers of locks to serialise changes to critical sections of the database. Transactions run concurrently until they try to acquire a conflicting lock, for example when they update the same row.
Do you need to block reads or writes in PostgreSQL?
However, not all DDL commands need to block reads or writes, some only block each other. Whether a transaction can acquire a lock depends on whether its “lock level” conflicts with that of the holder (s) of the lock. The PostgreSQL documentation gives a detailed overview of how different lock levels conflict.
What makes PostgreSQL unique among open source databases?
PostgreSQL is unique among open source databases in its support for complex, concurrent, ACID transactions. To make sure complex transactions can safely run at the same time, PostgreSQL uses several layers of locks to serialise changes to critical sections of the database.
Why is the ALTER TABLE blocked in PostgreSQL?
The table above tells us that an ALTER TABLE is blocked waiting for two UPDATE s to finish, while the UPDATE with SET y = 10 is waiting for the UPDATE with SET y = 5 to finish.
Why are my PostgreSQL queries not showing up in Citus?
If you’re using the Citus extension to Postgres to shard database tables across multiple nodes, one more thing to take into consideration is that queries might get blocked on row-level locks on one of the shards on a distributed Citus worker node—and if that happens, then those queries would not show up in pg_locks on the Citus coordinator node.
Is there way to disable constraint triggers in PostgreSQL?
PostGres appears to let me disable constraint triggers if I am a super user (I’m not, but I am logging in as the user that owns/created the objects) but that doesn’t seem to be quite what I want. The other option is to drop the constraint and then reinstate it.
How to resolve blocking problems that are caused by Lock?
If the lock that’s blocking other users is anything other than a TAB (table-level) lock that has a lock mode of S (shared), or X (exclusive), lock escalation is not the problem. In particular, if the TAB lock is an intent lock (such as a lock mode of IS, IU, or IX), this is not caused by lock escalation.