Hung Query with No Locking Issues - Mailing list pgsql-general

From Michael P. McDonnell
Subject Hung Query with No Locking Issues
Date
Msg-id CAHmCLHqDsYXQmNYROBQnFvtFnEkQxhD57Qz2h+wp4oOWRBYXVQ@mail.gmail.com
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Responses Re: Hung Query with No Locking Issues  (Tom Lane <tgl@sss.pgh.pa.us>)
List pgsql-general
Hey team - 
I have 2 stored procedures that need to run back to back. It could convert to a single one - but it's easier from a maintenance perspective to keep them separated.

The first procedure effectively is 
INSERT INTO table_b () SELECT ____ FROM _table_a_; 
COMMIT;

Total execution time - about 180s. Nothing in the pg_locks table and nothing in the pg_stat_activity table suggests anything is hung over.

The second procedure mutates table_b data into table_b_collapsed
INSERT INTO table_c () SELECT _____ FROM _table_b_ JOIN _table_b as b1_ JOIN _table_b as b2_ JOIN _table_b as b3_, etc...;
COMMIT;

The first time I run my second stored procedure - it hangs for up to 8 hours.
If I immediately cancel and re-run the second stored procedure it runs in 2 seconds.
If I let the query hang and rerun THE EXACT SAME QUERY in another tab of dbeaver - it runs in 2 seconds.

During the hang - there are no ungranted locks in pg_locks, nothing unusual in the stats_activity table that I know how to look for. CPU is locked at 100% for the postgres process during the duration of the hung query as well.

Speaking of cpu, this is running on a VMware VM with 8 CPUs and 192 GB of RAM as a solo VM on a 256 GB / 16 CPU host with SSDs backing the DB locally on the server (SATA 3 speeds I'm sure) and storage is sitting comfortably at 20% used and 1% inode utilization.

Not really sure what I'm missing here; I was having these problems even when they weren't a stored procedure. I was hoping pushing the commit immediately after the query would solve my problem. Any advice, pointers, would be appreciated.


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