This adds support for the `unsigned_long` type.
The type can be now used with the defined math function, both scalar and
MV'ed, arithmetic and binary comparison ones.
The `to_unsigned_long()` conversion function is also added.
This implements the `MV_DEDUPE` function that removes duplicates from
multivalues fields. It wasn't strictly in our list of things we need in
the first release, but I'm grabbing this now because I realized I needed
very similar infrastructure when I was trying to build grouping by
multivalued fields. In fact, I realized that I could use our
stringtemplate code generation to generate most of the complex parts.
This generates the actual body of `MV_DEDUPE`'s implementation and the
body of the `Block` accepting `BlockHash` implementations. It'll be
useful in the final step for grouping by multivalued fields.
I also got pretty curious about whether the `O(n^2)` or `O(n*log(n))`
algorithm for deduplication is faster. I'd been assuming that for all
reasonable sized inputs the `O(n^2)` bubble sort looking selection
algorithm was faster. So I measured it. And it's mostly true - even for
`BytesRef` if you have a dozen entries the selection algorithm is
faster. Lower overhead and stuff. Anyway, to measure it I had to
implement the copy-and-sort `O(n*log(n))` algorithm. So while I was
there I plugged it in and selected it in cases where the number of
inputs is large and the selection alogorithm is likely to be slower.
Adds an `mv_join` function that joins together multivalue string fields.
You can combine this with out fancy new `to_string` to join together any
multivalued fields into a string.
This adds a `mv_median` function that converts a multivalued field into
a single valued field by picking the median. If there are an even number
of values we return the average of the middle two numbers. If the input
type is `int` or `long` then the average rounds *down*.
