Re: server crashed with TRAP: FailedAssertion("!(!parallel_aware || pathnode->path.parallel_safe)"

On Sat, Jun 16, 2018 at 10:44 AM, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com> wrote:
> On Thu, Jun 14, 2018 at 9:54 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> Rajkumar Raghuwanshi <rajkumar(dot)raghuwanshi(at)enterprisedb(dot)com> writes:
>>> I am getting a server crash for below test case.
>>
>>> postgres=# select (select max((select t1.c2 from test t1 where t1.c1 =
>>> t2.c1))) from test t2;
>>> server closed the connection unexpectedly
>>
>> Reproduced here. The assert seems to be happening because
>> add_paths_to_append_rel is trying to create a parallel path for
>> an appendrel that is marked consider_parallel = false.
>>
>> This appears to be the fault of commit ab7271677, whose authors I've cc'd:
>> the stanza starting at about allpaths.c:1672 is bullheadedly creating a
>> parallel path whether that's allowed or not. Fixing it might be as simple
>> as adding "rel->consider_parallel" to the conditions there.
>>
>
> Yeah, or perhaps disallow creation of any partial paths at the first
> place like in attached. This will save us some work as well.
>

Attached patch contains test case as well. I have tried to come up
with some simple test, but couldn't come up with anything much simpler
than reported by Rajkumar, so decided to use the test case provided by
him.

Added to Open Items list.

--
With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com