Currently null and missing values are treated differently. Missing
values throw no_such_column. Null values return nullptr, std::nullopt
or throw null_column_value.
The api is a bit confusing since a function returning a std::optional
either returns std::nullopt or throws depending on why there is no
value.
With this patch series only get_nonnull throws and there is only one
exception type.
* https://github.com/espindola/scylla.git espindola/merge-null-and-missing-v2:
query-result-set: merge handling of null and missing values
Remove result_set_row::has
Return a reference from get_nonnull
077c639e42