(2014/09/10 16:57), Marko Tiikkaja wrote:
On 2014-09-10 04:25, Etsuro Fujita wrote:
(2014/09/09 18:57), Heikki Linnakangas wrote:
What's not clear to me is whether it make sense to do 1) without 2) ? Is
UPDATE .. LIMIT without support for an ORDER BY useful enough? And if we
apply this patch now, how much of it needs to be rewritten after 2) ? If
the answers are "yes" and "not much", then we should review this patch
now, and put 2) on the TODO list. Otherwise 2) should do done first.
My answers are "yes" but "completely rewritten".
Any particular reason for you to say that? Because an UPDATE might have
a RETURNING clause, all the updated tuples have to go through the
ModifyTable node one at a time. I don't see why we couldn't LIMIT there
after implementing #2.
The reason is because I think that after implementing #2, we should
re-implement this feature by extending the planner to produce a plan
tree such as ModifyTable+Limit+Append, maybe with LockRows below the
Limit node. Such an approach would prevent duplication of the LIMIT
code in ModifyTable, making the ModifyTable code more simple, I think.
Thanks,
Best regards,
Etsuro Fujita
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