Re: [HACKERS] Parallel Index-only scan

I  reviewed the patch. Overall it looks fine to me.

One comment,

>-       if (index->amcanparallel &&
>-           !index_only_scan &&
>+       if ((index->amcanparallel ||
>+           index_only_scan) &&

Why do we need to check for index_only_scan in the above condition. IIUC, index->amcanparallel is necessary for

parallel index scan to be chosen. We cannot chose parallel index only scan if index_only_scan is happening

without worrying about index->amcanparallel value. So OR-ing index->amcanparallel with index_only_scan is probably not

correct.

On Thu, Feb 16, 2017 at 1:06 AM, Robert Haas <robertmhaas@gmail.com> wrote:

This again needs minor rebasing but basically looks fine.  It's a
pretty straightforward extension of the parallel index scan work.

Please make sure that this is pgindent-clean - i.e. that when you
pgindent the files that it touches, pgindent doesn't change anything
of the same parts of the file that you've changed in the patch.  Also,
I believe Amit may have made some adjustments to the logic in
nodeIndexScan.c; if so, it would be good to make sure that the
nodeIndexOnlyScan.c changes match what was done there.  In particular,
he's got this:

                if (reset_parallel_scan && node->iss_ScanDesc->parallel_scan)
                        index_parallelrescan(node->iss_ScanDesc);

And you've got this:

+               if (reset_parallel_scan)
+                       index_parallelrescan(node->ioss_ScanDesc);