Re: Enabling parallelism for queries coming from SQL or other PL functions

On Thu, Feb 23, 2017 at 8:58 PM, Dilip Kumar <dilipbalaut(at)gmail(dot)com> wrote:
> On Thu, Feb 23, 2017 at 12:11 PM, Rafia Sabih
> <rafia(dot)sabih(at)enterprisedb(dot)com> wrote:
>
> 2. How are you protecting, if the outer select is running in parallel,
> then the function called from there should not run anything in
> parallel? This may allow worker launching another set of workers. Am
> I missing something?
>

We have a below check in standard_planner() (!IsParallelWorker())
which should prohibit generating parallel plan inside worker, if that
is what you are seeing, then we might need a similar check at other
places.

if ((cursorOptions & CURSOR_OPT_PARALLEL_OK) != 0 &&
IsUnderPostmaster &&
dynamic_shared_memory_type != DSM_IMPL_NONE &&
parse->commandType == CMD_SELECT &&
!parse->hasModifyingCTE &&
max_parallel_workers_per_gather > 0 &&
!IsParallelWorker() &&
!IsolationIsSerializable())
{
/* all the cheap tests pass, so scan the query tree */
glob->maxParallelHazard = max_parallel_hazard(parse);
glob->parallelModeOK = (glob->maxParallelHazard != PROPARALLEL_UNSAFE);
}

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