On 11/21/2012 08:04 AM, Heikki Linnakangas wrote:
On 21.11.2012 01:53, Tom Lane wrote:
I think the more interesting question is what cases wouldn't be covered
by such a rule. Typically you need to use OFFSET 0 in situations where
the planner has guessed wrong about costs or rowcounts, and I think
people are likely using WITH for that as well. Should we be telling
people that they ought to insert OFFSET 0 in WITH queries if they want
to be sure there's an optimization fence?
Yes, I strongly feel that we should. Writing a query using WITH often
makes it more readable. It would be a shame if people have to refrain
from using it, because the planner treats it as an optimization fence.
If we're going to do it can we please come up with something more
intuitive and much, much more documented than "OFFSET 0"? And if/when we
do this we'll need to have big red warnings all over then release notes,
since a lot of people I know will need to do some extensive remediation
before moving to such a release.
cheers
andrew
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