Previously compute_bounds was assuming that primary-key columns are
restricted by exactly one equality, resulting in the following error:
query 'select p from t where p=1 and p=1' failed:
std::bad_variant_access (std::get: wrong index for variant)
This patch removes that assumption and deals correctly with the
multiple-equalities case. As a byproduct, it also stops raising
"invalid null value" exceptions for null RHS values.
Signed-off-by: Dejan Mircevski <dejan@scylladb.com>
4bb1107652