Postgres extremely slow after upgrade from Version 10 to 11
Question
Related to this:PostgreSQL extremely slow after upgrade from 9.3 to 9.4 but trying to understand better...
My queries was slow after upgrading to Postgres Version 11.5 from 10.7
I first ran ANALYZE
on the DB but still was slow!
so I can VACUUM ANALYZE
on the DB, and was still slow...
as a last resort, I am running VACUUM FULL ANALYZE
on a table by table basis using psycopg2 with autocommit on (http://initd.org/psycopg/docs/connection.html#connection.autocommit) to be able to run it in psycopg2
one table is taking hours to do ... while I wait, I can't help but wonder what went wrong. The reduction of the query performance was mainly from UPSERT.
Solution 2
The culprit was even with VACUUM FULL ANALYZE
, query planner was still not using indexes in many cases.
Solved by forcing SET enable_seqscan = OFF;
, after few autovacuums, it re-adjusted.
OTHER TIPS
The output of pg_upgrade includes this:
...
Upgrade Complete
----------------
Optimizer statistics are not transferred by pg_upgrade so,
once you start the new server, consider running:
./analyze_new_cluster.sh
...
We found horrible performance straight after the upgrade until we ran this, lesson learned to read the output :)