Method DispatchBest

cpp/src/arrow/compute/kernels/scalar_if_else.cc:1245–1287

  using ScalarFunction::ScalarFunction;

  Result<const Kernel*> DispatchBest(std::vector<TypeHolder>* types) const override {
    RETURN_NOT_OK(CheckArity(types->size()));

    using arrow::compute::detail::DispatchExactImpl;
    // Do not DispatchExact here because it'll let through something like (bool,
    // timestamp[s], timestamp[s, "UTC"])

    // if 0th type is null, replace with bool
    if (types->at(0).id() == Type::NA) {
      (*types)[0] = boolean();
    }

    // if-else 0'th type is bool, so skip it
    TypeHolder* left_arg = &(*types)[1];
    constexpr size_t num_args = 2;

    internal::ReplaceNullWithOtherType(left_arg, num_args);

    // If both are identical dictionary types, dispatch to the dictionary kernel
    // TODO(ARROW-14105): apply implicit casts to dictionary types too
    TypeHolder* right_arg = &(*types)[2];
    if (is_dictionary(left_arg->id()) && left_arg->type->Equals(*right_arg->type)) {
      auto kernel = DispatchExactImpl(this, *types);
      DCHECK(kernel);
      return kernel;
    }

    internal::EnsureDictionaryDecoded(left_arg, num_args);

    if (auto type = internal::CommonNumeric(left_arg, num_args)) {
      internal::ReplaceTypes(type, left_arg, num_args);
    } else if (auto type = internal::CommonTemporal(left_arg, num_args)) {
      internal::ReplaceTypes(type, left_arg, num_args);
    } else if (auto type = internal::CommonBinary(left_arg, num_args)) {
      internal::ReplaceTypes(type, left_arg, num_args);
    } else if (HasDecimal(*types)) {
      RETURN_NOT_OK(CastDecimalArgs(left_arg, num_args));
    }

    if (auto kernel = DispatchExactImpl(this, *types)) return kernel;

    return arrow::compute::detail::NoMatchingKernel(this, *types);
  }
};

void AddNullIfElseKernel(const std::shared_ptr<IfElseFunction>& scalar_function) {