On 24/02/10 22:47, Dave Crooke wrote:
I'd imagine it would be possible to have a query planner optimization
that would convert Garrett's DISTINCT ON syntax to do what I was
trying to, by realizing that DISTINCT ON X ... ORDER BY Y DESC is
going to return the the one row for each X which has the highest value
of Y, and so use a MAX-structured accumulation instead of a sort.
Why is there only one row? For city temperatures, that seems unlikely.
In the event of more than one row does your algorithm give repeatable
results?
--
Richard Huxton
Archonet Ltd
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