Defer to C++ equality and hashing for pylibcudf DataType and Aggregat…

…ion objects (rapidsai#15732)

Since the C++ layer provides implementations of these, use them, rather than redoing an implementation. This avoids things ever getting out of sync.

Authors:
  - Lawrence Mitchell (https://github.com/wence-)

Approvers:
  - Vyas Ramasubramani (https://github.com/vyasr)

URL: rapidsai#15732

python/cudf/cudf/_lib/pylibcudf/aggregation.pyx

@@ -79,6 +79,14 @@ cdef class Aggregation:
             "Aggregations should not be constructed directly. Use one of the factories."
         )
 
+    def __eq__(self, other):
+        return type(self) is type(other) and (
+            dereference(self.c_obj).is_equal(dereference((<Aggregation>other).c_obj))
+        )
+
+    def __hash__(self):
+        return dereference(self.c_obj).do_hash()
+
     # TODO: Ideally we would include the return type here, but we need to do so
     # in a way that Sphinx understands (currently have issues due to
     # https://github.com/cython/cython/issues/5609).

python/cudf/cudf/_lib/pylibcudf/libcudf/aggregation.pxd

@@ -1,4 +1,5 @@
 # Copyright (c) 2020-2024, NVIDIA CORPORATION.
+from libc.stddef cimport size_t
 from libc.stdint cimport int32_t
 from libcpp cimport bool
 from libcpp.memory cimport unique_ptr
@@ -51,6 +52,8 @@ cdef extern from "cudf/aggregation.hpp" namespace "cudf" nogil:
     cdef cppclass aggregation:
         Kind kind
         unique_ptr[aggregation] clone()
+        size_t do_hash() noexcept
+        bool is_equal(const aggregation const) noexcept
 
     cdef cppclass rolling_aggregation(aggregation):
         pass

python/cudf/cudf/_lib/pylibcudf/libcudf/types.pxd

@@ -88,8 +88,9 @@ cdef extern from "cudf/types.hpp" namespace "cudf" nogil:
         data_type(const data_type&) except +
         data_type(type_id id) except +
         data_type(type_id id, int32_t scale) except +
-        type_id id() except +
-        int32_t scale() except +
+        type_id id() noexcept
+        int32_t scale() noexcept
+        bool operator==(const data_type&, const data_type&) noexcept
 
     cpdef enum class interpolation(int32_t):
         LINEAR

python/cudf/cudf/_lib/pylibcudf/types.pyx

@@ -47,9 +47,9 @@ cdef class DataType:
         return self.c_obj.scale()
 
     def __eq__(self, other):
-        if not isinstance(other, DataType):
-            return False
-        return self.id() == other.id() and self.scale() == other.scale()
+        return type(self) is type(other) and (
+            self.c_obj == (<DataType>other).c_obj
+        )
 
     @staticmethod
     cdef DataType from_libcudf(data_type dt):