From: | Etsuro Fujita <fujita(dot)etsuro(at)lab(dot)ntt(dot)co(dot)jp> |
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To: | Rukh Meski <rukh(dot)meski(at)gmail(dot)com>, "pgsql-hackers(at)postgresql(dot)org" <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: LIMIT for UPDATE and DELETE |
Date: | 2014-08-29 10:20:31 |
Message-ID: | 540053EF.9090708@lab.ntt.co.jp |
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Lists: | pgsql-hackers |
(2014/08/25 15:48), Etsuro Fujita wrote:
> (2014/08/15 6:18), Rukh Meski wrote:
>> Based on the feedback on my previous patch, I've separated only the
>> LIMIT part into its own feature. This version plays nicely with
>> inheritance. The intended use is splitting up big UPDATEs and DELETEs
>> into batches more easily and efficiently.
>
> Before looking into the patch, I'd like to know the use cases in more
> details.
Thanks for the input, Amit, Kevin and Jeff! I understand that the patch
is useful.
I've looked at the patch a bit closely. Here is my initial thought
about the patch.
The patch places limit-counting inside ModifyTable, and works well for
inheritance trees, but I'm not sure that that is the right way to go. I
think that this feature should be implemented in the way that we can
naturally extend it to the ORDER-BY-LIMIT case in future. But honestly
the patch doesn't seem to take into account that, I might be missing
something, though. What plan do you have for the future extensibility?
I think that the approach discussed in [1] would be promissing, so ISTM
that it would be better to implement this feature by allowing for plans
in the form of eg, ModifyTModifyTable+Limit+Append.
Thanks,
[1] http://www.postgresql.org/message-id/26819.1291133045@sss.pgh.pa.us
Best regards,
Etsuro Fujita
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