Querying an integer field with a fill value will cause a cast error
because the underlying type is a float64 rather than an int64. Add a
function that will coerce the value to the correct type.
It may be more appropriate in the future to have the fill iterator read
the underlying iterator and cast to the appropriate type rather than
coerce the fill value to the correct type, but this solution works for
our current scenario well.
Jonathan A. Sternberg