Thread: lwlock:LockManager wait_events
experts,
we faced into a lot of lwlock:LockManager wait-events , all of these queries are "select ..." , there are other several session are doing DML, insert/update/delete on same table. Did these DML transactions holding "transactionid" and "tuple" lock blocking "select" on lwlock:LockManager ?
Thanks,
James
On Fri, 2024-10-25 at 14:36 +0800, James Pang wrote: > we faced into a lot of lwlock:LockManager wait-events , all of these queries are "select ..." , > there are other several session are doing DML, insert/update/delete on same table. > Did these DML transactions holding "transactionid" and "tuple" lock blocking "select" on lwlock:LockManager ? This is not about waiting for a lock. Rather, it means that very many sessions are trying to take a lock. They have to grab the lock manager to take a lock, and the competition for that resource is the bottleneck. It is hard to say what is the root cause without further analysis, but very often the cause is that you have too many connections to the database. Using an effective connection pool *might* solve that particular problem. Yours, Laurenz Albe
You may find this helpful, the advice is not specific to RDS.
https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/wait-event.lw-lock-manager.html
HTH.
https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/wait-event.lw-lock-manager.html
HTH.
On Fri, 25 Oct 2024 at 18:36, Laurenz Albe <laurenz.albe@cybertec.at> wrote:
On Fri, 2024-10-25 at 14:36 +0800, James Pang wrote:
> we faced into a lot of lwlock:LockManager wait-events , all of these queries are "select ..." ,
> there are other several session are doing DML, insert/update/delete on same table.
> Did these DML transactions holding "transactionid" and "tuple" lock blocking "select" on lwlock:LockManager ?
This is not about waiting for a lock. Rather, it means that very many sessions are trying
to take a lock. They have to grab the lock manager to take a lock, and the competition for
that resource is the bottleneck.
It is hard to say what is the root cause without further analysis, but very often the
cause is that you have too many connections to the database. Using an effective connection
pool *might* solve that particular problem.
Yours,
Laurenz Albe
On Fri, 25 Oct 2024, 14:36 James Pang, <jamespang886@gmail.com> wrote:
experts,we faced into a lot of lwlock:LockManager wait-events , all of these queries are "select ..." , there are other several session are doing DML, insert/update/delete on same table. Did these DML transactions holding "transactionid" and "tuple" lock blocking "select" on lwlock:LockManager ?
Which version of PostgreSQL?
Are these all same query or variant of same query (with different parameters)?
What's the schema (you can redact column names) for the tables involved in the select query which is blocked/waiting on lock_manager?
Thanks,James