Hi Postgres Experts,
Please help me on a query tuning.
Postgres verson: 11.5
This database has been migrated from oracle 12c to postgres. In Oracle
query executes in 2-3 secs, but in postgres it hangs forever. There are no
transactions at this time, I am stuck at first run after migration.
My analysis:
I have done vacuum full , analyze , even with 100% samples using a much
higher value of default_statistics_target.
Also tried different hints using pg_hint_plan extension. Overall cost
reduces, but actual run hangs forever.
I think problem is with correlated subquery join condition.
If "and pdtaltrelt*%*_.tenant_dkby=pdtaltrelt0_.tenant_dkby" condition is
removed from both subqueries, result comes in secs(I understand that would
be skipping correlated join)
SQL> select count(*) from pdtalt_rel_to_tenant_rel;
267216
SQL> select count(distinct tenant_dkby) from pdtalt_rel_to_tenant_rel;
3
Table DDLs , query plan and parameter configuration available at below git
link:
https://github.com/bansalsaket/PG_correlated_subquery_slowness
I have 16 GB , 4 CPU , rhel 7 machine.
Thanks for help in advance, let me know if any additional information is
required
