From: | Etsuro Fujita <fujita(dot)etsuro(at)lab(dot)ntt(dot)co(dot)jp> |
---|---|
To: | Robert Haas <robertmhaas(at)gmail(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | Rushabh Lathia <rushabh(dot)lathia(at)gmail(dot)com>, Thom Brown <thom(at)linux(dot)com>, Stephen Frost <sfrost(at)snowman(dot)net>, Albe Laurenz <laurenz(dot)albe(at)wien(dot)gv(dot)at>, Shigeru Hanada <shigeru(dot)hanada(at)gmail(dot)com>, PostgreSQL-development <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Optimization for updating foreign tables in Postgres FDW |
Date: | 2016-03-10 11:50:33 |
Message-ID: | 56E15F89.9010904@lab.ntt.co.jp |
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Lists: | pgsql-hackers |
On 2016/03/10 19:51, Robert Haas wrote:
> On Wed, Mar 9, 2016 at 3:30 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>> Robert Haas <robertmhaas(at)gmail(dot)com> writes:
>>> Just taking a guess here, you might be thinking that instead of
>>> something like this...
>>
>>> Update on public.ft2
>>> -> Foreign Update on public.ft2
>>
>>> We could boil it all the way down to this:
>>
>>> Foreign Update on public.ft2
>>
>> Exactly. I'm not claiming that that would be particularly faster, but
>> it would eliminate a whole bunch of seriously ugly stuff that's in
>> this patch.
>>> But can you, really? What if the UPDATE is targeting an inheritance
>>> hierarchy containing some local tables and some remote tables?
>>
>> I don't really see why that couldn't be made to work. You'd end up
>> with ForeignUpdates on the remote tables and a ModifyTable handling
>> the rest.
>
> I don't get it. I mean, what's the parent node going to be? If it's
> the ModifyTable, then the plan tree looks the same as what this
> already does. If not, then what?
I don't get it, either. If the ForeignUpdates would be executed
separately from the ModifyTable, how would the query's reported row
count (ie, estate->es_processed) be handled?
> Just to recap the history, this patch was rewritten, criticized by
> Stephen and you and rewritten to match your feedback. Then, both of
> you ignored it for a long time while I and others but a lot of work
> into it. Now, we're up against the deadline for this release and you
> don't like it again. Well, OK. If you want to rewrite it into some
> form you think is better, I'm cool with that. But it would be really
> unfair if this slipped out of this release after so much work has been
> put into making it match the design ideas that *you* put forward just
> because, at the eleventh hour, you now have new ones. Personally, I
> think we should just commit the darned thing and you can rewrite it
> later if you want. If you want to rewrite it now instead, I can live
> with that, too. But let's figure out how we're going to move this
> forward.
I agree with Robert.
Best regards,
Etsuro Fujita
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