Re: range_agg

I came across an interesting thing, namely multirange_canonicalize()'s
use of qsort_arg with a callback of range_compare(). range_compare()
calls range_deserialize() (non-trivial parsing) for each input range;
multirange_canonicalize() later does a few extra deserialize calls of
its own. Call me a premature optimization guy if you will, but I think
it makes sense to have a different struct (let's call it
"InMemoryRange") which stores the parsed representation of each range;
then we can deserialize all ranges up front, and use that as many times
as needed, without having to deserialize each range every time.

While I'm at this, why not name the new file simply multiranges.c
instead of multirangetypes.c?

--
Álvaro Herrera https://www.2ndQuadrant.com/
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