REV: move unique, _get_unique_index to ExtensionIndex

pandas/core/indexes/datetimelike.py

@@ -110,17 +110,6 @@ class DatetimeIndexOpsMixin(ExtensionIndex, ExtensionOpsMixin):
     def is_all_dates(self) -> bool:
         return True
 
-    def unique(self, level=None):
-        if level is not None:
-            self._validate_index_level(level)
-
-        result = self._data.unique()
-
-        # Note: if `self` is already unique, then self.unique() should share
-        #  a `freq` with self.  If not already unique, then self.freq must be
-        #  None, so again sharing freq is correct.
-        return self._shallow_copy(result._data)
-
     @classmethod
     def _create_comparison_method(cls, op):
         """

pandas/core/indexes/extension.py

@@ -176,3 +176,19 @@ def take(self, indices, axis=0, allow_fill=True, fill_value=None, **kwargs):
             na_value=self._na_value,
         )
         return type(self)(taken, name=self.name)
+
+    def unique(self, level=None):
+        if level is not None:
+            self._validate_index_level(level)
+
+        result = self._data.unique()
+        return self._shallow_copy(result)
+
+    def _get_unique_index(self, dropna=False):
+        if self.is_unique and not dropna:
+            return self
+
+        result = self._data.unique()
+        if dropna and self.hasnans:
+            result = result[~result.isna()]
+        return self._shallow_copy(result)

pandas/core/indexes/period.py

@@ -583,15 +583,6 @@ def get_indexer_non_unique(self, target):
         indexer, missing = self._int64index.get_indexer_non_unique(target)
         return ensure_platform_int(indexer), missing
 
-    def _get_unique_index(self, dropna=False):
-        if self.is_unique and not dropna:
-            return self
-
-        result = self._data.unique()
-        if dropna and self.hasnans:
-            result = result[~result.isna()]
-        return self._shallow_copy(result)
-
     def get_loc(self, key, method=None, tolerance=None):
         """
         Get integer location for requested label