>
> Right, but OTOH, if we assign parallel workers by default, then it is
> quite possible that it would result in much worse plans. Consider a
> case where partition hierarchy has 1000 partitions and only one of
> them is big enough to allow parallel workers. Now in this case, with
> your proposed fix it will try to scan all the partitions in parallel
> workers which I think can easily result in bad performance.
Right. But, there can also be a case where 999 partitions are large
and eligible for PSS. In such case as well, PSS won't be selected.
I think
> the right way to make such plans parallel is by using Parallel Append
> node (https://commitfest.postgresql.org/13/987/). Alternatively, if
> you want to force parallelism in cases like the one you have shown in
> example, you can use Alter Table .. Set (parallel_workers = 1).
Okay, I was not aware of Parallel Append. Thanks.
With Regards,
Ashutosh Sharma
EnterpriseDB: http://www.enterprisedb.com
