Re: initial pruning in parallel append

On Wed, Aug 9, 2023 at 8:57 AM Amit Langote <amitlangote09@gmail.com> wrote:
> I checked enough to be sure that IsParallelWorker() is reliable at the
> time of ExecutorStart() / ExecInitNode() in ParallelQueryMain() in a
> worker.   However, ParallelWorkerContext is not available at that
> point.  Here's the relevant part of ParallelQueryMain():
>
>     /* Start up the executor */
>     queryDesc->plannedstmt->jitFlags = fpes->jit_flags;
>     ExecutorStart(queryDesc, fpes->eflags);
>
>     /* Special executor initialization steps for parallel workers */
>     queryDesc->planstate->state->es_query_dsa = area;
>     if (DsaPointerIsValid(fpes->param_exec))
>     {
>         char       *paramexec_space;
>
>         paramexec_space = dsa_get_address(area, fpes->param_exec);
>         RestoreParamExecParams(paramexec_space, queryDesc->estate);
>     }
>     pwcxt.toc = toc;
>     pwcxt.seg = seg;
>     ExecParallelInitializeWorker(queryDesc->planstate, &pwcxt);
>
> BTW, we do also use IsParallelWorker() in ExecGetRangeTableRelation()
> which also probably only runs during ExecInitNode(), same as
> ExecInitPartitionPruning() that this patch adds it to.

I don't know if that's a great idea, but I guess if we're already
doing it, it doesn't hurt to expand the use a little bit.

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