On Mon, Aug 28, 2017 at 6:01 PM, Tom Lane <tgl@sss.pgh.pa.us> wrote:
> Amit Kapila <amit.kapila16@gmail.com> writes:
>> With this change, it is quite possible that during rescans workers
>> will not do any work.
>
> Um, what's different about that than before?
>
Earlier, we perform the rescan of all the nodes before ExecProcNode,
so workers will always start (restart) after the scan descriptor is
initialized. Now, as evident in the discussion in this thread that
was not the right thing for gather merge as some of the nodes like
Sort does some optimization due to which rescan for the lower nodes
will never be called. So, we need to ensure in some way that we don't
skip rescanning in such nodes and one way to achieve that is what you
have done in the patch, but it seems to have some side effect.
--
With Regards,
Amit Kapila.
EnterpriseDB: http://www.enterprisedb.com