add Int8Index

Author: tp

pandas/_libs/index_class_helper.pxi.in

@@ -12,9 +12,13 @@ WARNING: DO NOT edit .pxi FILE directly, .pxi is generated from .pxi.in
 
 # name, dtype, ctype
 dtypes = [('Float64', 'float64', 'float64_t'),
-          ('UInt64', 'uint64', 'uint64_t'),
           ('Int64', 'int64', 'int64_t'),
-          ('Object', 'object', 'object')]
+          ('Int32', 'int32', 'int32_t'),
+          ('Int16', 'int16', 'int16_t'),
+          ('Int8', 'int8', 'int8_t'),
+          ('UInt64', 'uint64', 'uint64_t'),
+          ('Object', 'object', 'object'),
+          ]
 }}
 
 {{for name, dtype, ctype in dtypes}}

pandas/core/indexes/category.py

@@ -83,7 +83,11 @@ class CategoricalIndex(Index, accessor.PandasDelegate):
     """
 
     _typ = 'categoricalindex'
-    _engine_type = libindex.Int64Engine
+
+    @property
+    def _engine_type(self):
+        type_name = self.codes.dtype.name.capitalize()
+        return getattr(libindex, "{}Engine".format(type_name))
     _attributes = ['name']
 
     def __new__(cls, data=None, categories=None, ordered=None, dtype=None,
@@ -377,7 +381,7 @@ def argsort(self, *args, **kwargs):
     def _engine(self):
 
         # we are going to look things up with the codes themselves
-        return self._engine_type(lambda: self.codes.astype('i8'), len(self))
+        return self._engine_type(lambda: self.codes, len(self))
 
     # introspection
     @cache_readonly