Re: Partition-wise join for join between (declaratively) partitioned tables

From: Amit Langote <Langote_Amit_f8(at)lab(dot)ntt(dot)co(dot)jp>
To: Robert Haas <robertmhaas(at)gmail(dot)com>, Ashutosh Bapat <ashutosh(dot)bapat(at)enterprisedb(dot)com>
Cc: Etsuro Fujita <fujita(dot)etsuro(at)lab(dot)ntt(dot)co(dot)jp>, Thomas Munro <thomas(dot)munro(at)enterprisedb(dot)com>, Rafia Sabih <rafia(dot)sabih(at)enterprisedb(dot)com>, Rajkumar Raghuwanshi <rajkumar(dot)raghuwanshi(at)enterprisedb(dot)com>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: Partition-wise join for join between (declaratively) partitioned tables
Date: 2017-09-11 07:04:05
Message-ID: 16c95b91-0fe4-6279-05a4-f97885cdcf41@lab.ntt.co.jp
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On 2017/09/09 9:58, Robert Haas wrote:
> I'm a bit suspicious about the fact that there are now executor
> changes related to the PlanRowMarks. If the rowmark's prti is now the
> intermediate parent's RT index rather than the top-parent's RT index,
> it'd seem like that'd matter somehow. Maybe it doesn't, because the
> code that cares about prti seems to only care about whether it's
> different from rti.

Yes, it doesn't matter. The important point though is that nothing we
want to do in the short term requires us to set a child PlanRowMark's prti
to its immediate parent's RT index, as I also mentioned in reply to Ashutosh.

> But if that's true everywhere, then why even
> change this? I think we might be well off not to tinker with things
> that don't need to be changed.

+1.

> Apart from that concern, now that I understand (from my own failed
> attempt and some off-list discussion) why this patch works the way it
> does, I think this is in fairly good shape.

I too think so, except we still need to incorporate changes to
add_paths_to_append_rel() necessary to correctly set partitioned_rels, as
I explained in reply Ashutosh.

Thanks,
Amit

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