On Thu, Jul 18, 2019 at 2:55 AM Etsuro Fujita <etsuro.fujita@gmail.com> wrote:
> I.e., partition_bounds_merge() is performed for each pair of input
> partitioned relations for a join relation in try_partitionwise_join().
> Since partition_bounds_merge() would need a lot of CPU cycles, I don't
> think this is acceptable; ISTM that some redesign is needed to avoid
> this. I'm wondering that once we successfully merged partition bounds
> from a pair of input partitioned relations for the join relation, by
> using the merged partition bounds, we could get the lists of matching
> to-be-joined partitions for subsequent pairs of input partitioned
> relations for the join relation in a more efficient way than by
> performing partition_bounds_merge() as proposed in the patch.
I don't know whether partition_bounds_merge() is well-implemented; I
haven't looked. But in general I don't see an alternative to doing
some kind of merging on each pair of input relations. That's just how
planning works, and I don't see why it should need to be prohibitively
expensive. I might be missing something, though; do you have an idea?
--
Robert Haas
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