Re: Parallel Seq Scan

On Fri, Sep 18, 2015 at 5:31 PM, Amit Kapila <amit(dot)kapila16(at)gmail(dot)com>
wrote:
>
> On Thu, Sep 17, 2015 at 4:44 PM, Robert Haas <robertmhaas(at)gmail(dot)com>
wrote:
> >
> > I haven't studied the planner logic in enough detail yet to have a
> > clear opinion on this. But what I do think is that this is a very
> > good reason why we should bite the bullet and add outfuncs/readfuncs
> > support for all Plan nodes. Otherwise, we're going to have to scan
> > subplans for nodes we're not expecting to see there, which seems
> > silly. We eventually want to allow all of those nodes in the worker
> > anyway.
> >
>
> makes sense to me. There are 39 plan nodes and it seems we have
> support for all of them in outfuncs and needs to add for most of them
> in readfuncs.
>

Attached patch (read_funcs_v1.patch) contains support for all the plan
and other nodes (like SubPlan which could be required for worker) except
CustomScan node. CustomScan contains TextOutCustomScan and doesn't
contain corresponding Read function pointer, we could add the support for
same, but I am not sure if CustomScan is required to be passed to worker
in near future, so I am leaving it for now.

To verify the patch, I have done 2 things, first I have added elog to
the newly supported read funcs and then in planner, I have used
nodeToString and stringToNode on planned_stmt and then used the
newly generated planned_stmt for further execution. After making these
changes, I have ran make check-world and ensures that it covers all the
newly added nodes.

Note, that as we don't populate funcid's in expressions during read, the
same has to be updated by traversing the tree and updating in different
expressions based on node type. Attached patch (read_funcs_test_v1)
contains the changes required for testing the patch. I am not very sure
about what do about some of the ForeignScan fields (fdw_private) in order
to update the funcid as the data in those expressions could be FDW specific.
This is anyway for test, so doesn't matter much, but the same will be
required to support read of ForeignScan node by worker.

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