3rd change after review

Author: makbigc

pandas/core/reshape/merge.py

@@ -20,7 +20,7 @@
  is_datetime64tz_dtype, is_datetimelike, is_dtype_equal, is_float_dtype,
  is_int64_dtype, is_int_or_datetime_dtype, is_integer, is_integer_dtype,
  is_list_like, is_number, is_numeric_dtype, is_extension_array_dtype,
- needs_i8_conversion)
+ is_period_dtype, needs_i8_conversion)
 from pandas.core.dtypes.missing import isnull, na_value_for_dtype
 
 from pandas import Categorical, DataFrame, Index, MultiIndex, Series, Timedelta
@@ -1608,6 +1608,12 @@ def _factorize_keys(lk, rk, sort=True):
 
  lk = ensure_int64(lk.codes)
  rk = ensure_int64(rk)
+ elif (is_period_dtype(lk) and
+ is_period_dtype(rk) and
+ lk.dtype == rk.dtype):
+ klass = libhashtable.Factorizer
+ lk = ensure_object(lk)
+ rk = ensure_object(rk)
  elif (is_extension_array_dtype(lk) and
  is_extension_array_dtype(rk) and
  lk.dtype == rk.dtype):