Re: Server crashed with TRAP: FailedAssertion("!(parallel_workers > 0)" when partitionwise_aggregate true.

On Fri, Jun 22, 2018 at 2:26 AM, Rajkumar Raghuwanshi
<rajkumar(dot)raghuwanshi(at)enterprisedb(dot)com> wrote:
> I have applied patch and checked reported issue. Patch applied cleanly and
> issues not reproducible any more.

Committed, with a few changes:

- Renamed found_partially_grouped_child to partial_grouping_valid.
The old name seemed to me to be a poor choice, because it sounds from
the name like it gets set to true whenever we've found at least one
partially grouped child, whereas really it gets set to false whenever
we've failed to find at least one partially grouped child. The new
name is also more like the names in add_paths_to_append_rel.

- Modified the wording of the comment.

- Omitted the new assertion in add_paths_to_append_rel. I doubt
whether that's correct. I don't see any obvious reason why
live_childrels can't be NIL there, and further down I see this:

/*
* If we found unparameterized paths for all children, build
an unordered,
* unparameterized Append path for the rel. (Note: this is correct even
* if we have zero or one live subpath due to constraint exclusion.)
*/

If it's not possible to have no live_childrels, then that comment is
highly suspect.

Also, even if this assertion *is* correct, I think it needs a better
comment explaining why it's correct, because there isn't anything
obvious in set_append_rel_pathlist that keeps IS_DUMMY_REL() from
being true for every child.

--
Robert Haas
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