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

On Fri, Mar 24, 2017 at 5:57 AM, Rafia Sabih
<rafia(dot)sabih(at)enterprisedb(dot)com> wrote:
>> I suspect that code fails to achieve its goals anyway. At the top of
>> exec_eval_expr(), you call exec_prepare_plan() and unconditionally
>> pass CURSOR_OPT_PARALLEL_OK, so when that function returns, expr->plan
>> might now be a parallel plan. If we reach the call to
>> exec_run_select() further down in that function, and if we happen to
>> pass false, it's not going to matter, because exec_run_select() is
>> going to find the plan already initialized.
>>
> True, fixed.
> The attached patch is to be applied over [1].

After some scrutiny I didn't find anything particularly wrong with
this, with the exception that exec_eval_expr() was passing false as
the parallelOK argument to exec_run_select(), which is inconsistent
with that function's earlier use of CURSOR_OPT_PARALLEL_OK to plan the
same query. I fixed that by ripping out the parallelOK argument
altogether and just passing CURSOR_OPT_PARALLEL_OK when portalP ==
NULL. The only reason I added parallelOK in the first place was
because of that RETURN QUERY stuff which subsequent study has shown to
be misguided.

Committed that way; please let me know if you see any problems.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
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