Re: [HACKERS] CLUSTER command progress monitor

On 2019/03/06 1:13, Robert Haas wrote:
> On Tue, Mar 5, 2019 at 3:56 AM Tatsuro Yamada
> <yamada.tatsuro@lab.ntt.co.jp> wrote:
>>>> === Discussion points ===
>>>>
>>>>     - Progress counter for "3. sorting tuples" phase
>>>>        - Should we add pgstat_progress_update_param() in tuplesort.c like a
>>>>          "trace_sort"?
>>>>          Thanks to Peter Geoghegan for the useful advice!
>>>
>>> How would we avoid an abstraction violation?
>>
>> Hmm... What do you mean an abstraction violation?
>> If it is difficult to solve, I'd not like to add the progress counter for the sorting tuples.
> 
> What I mean is... I think it would be useful to have this counter, but
> I'm not sure how the tuplesort code would know to update the counter
> in this case and not in other cases.  The tuplesort code is used for
> lots of things; we can't update a counter for CLUSTER if the tuplesort
> is being used for CREATE INDEX or a Sort node in a query or whatever.
> So my question is how we would indicate to the tuplesort that it needs
> to do the counter update, and whether that would end up making for
> ugly code.

Thanks for your explanation!
I understood that now. I guess it means an API to get a progress for sort processing,
so let us just put it aside now. I'd like to leave that as is for an appropriate person.

Regards,
Tatsuro Yamada