(2014/09/17 1:58), Robert Haas wrote:
On Tue, Sep 16, 2014 at 11:31 AM, Kevin Grittner <kgri...@ymail.com> wrote:
Etsuro Fujita <fujita.ets...@lab.ntt.co.jp> 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.

IIUC, the patch doesn't support OFFSET with UPDATE/DELETE ... LIMIT.  Is
that OK?  When we support ORDER BY ... LIMIT/OFFSET, we will also be
allowing for OFFSET with UPDATE/DELETE ... LIMIT.  So, ISTM it would be
better for the patch to support OFFSET at this point.  No?

Without ORDER BY you really would have no idea *which* rows the
OFFSET would be skipping.  Even more dangerously, you might *think*
you do, and get a surprise when you see the results (if, for
example, a seqscan starts at a point other than the start of the
heap, due to a concurrent seqscan from an unrelated query).  It
might be better not to provide an illusion of a degree of control
you don't have, especially for UPDATE and DELETE operations.

Fair point, but I'd lean toward including it.  I think we all agree
the end goal is ORDER BY .. LIMIT, and there OFFSET certainly has
meaning.  If we don't include it now, we'll just end up adding it
later.  It makes for fewer patches, and fewer changes for users, if we
do it all at once.

I agree with Robert.

Rukh, what do you think as an author?


Best regards,
Etsuro Fujita

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