PERF: speed up slice indexing on Series with string keys

The patch avoids scanning the whole slice in Index.is_all_dates check.

Author: immerrr

doc/source/release.rst

@@ -74,6 +74,7 @@ Improvements to existing features
   the func (:issue:`6289`)
 - ``plot(legend='reverse')`` will now reverse the order of legend labels for most plot kinds.
   (:issue:`6014`)
+- improve performance of slice indexing on Series with string keys (:issue:`6341`)
 
 .. _release.bug_fixes-0.14.0:
 

doc/source/v0.14.0.txt

@@ -46,7 +46,7 @@ Enhancements
   and parse accordingly. (:issue:`6223`)
 - ``plot(legend='reverse')`` will now reverse the order of legend labels for
   most plot kinds. (:issue:`6014`)
-
+- improve performance of slice indexing on Series with string keys (:issue:`6341`)
 
 Performance
 ~~~~~~~~~~~

pandas/core/index.py

@@ -9,7 +9,7 @@
 import pandas.lib as lib
 import pandas.algos as _algos
 import pandas.index as _index
-from pandas.lib import Timestamp
+from pandas.lib import Timestamp, is_datetime_array
 from pandas.core.base import FrozenList, FrozenNDArray
 
 from pandas.util.decorators import cache_readonly, deprecate
@@ -577,7 +577,7 @@ def is_type_compatible(self, typ):
 
     @cache_readonly
     def is_all_dates(self):
-        return self.inferred_type == 'datetime'
+        return is_datetime_array(self.values)
 
     def __iter__(self):
         return iter(self.values)

vb_suite/indexing.py

@@ -7,7 +7,7 @@
 """
 
 #----------------------------------------------------------------------
-# Series.__getitem__, get_value
+# Series.__getitem__, get_value, __getitem__(slice)
 
 setup = common_setup + """
 tm.N = 1000
@@ -29,6 +29,15 @@
                            name='series_get_value',
                            start_date=datetime(2011, 11, 12))
 
+
+setup = common_setup + """
+index = tm.makeStringIndex(1000000)
+s = Series(np.random.rand(1000000), index=index)
+"""
+series_getitem_slice = Benchmark("s[:800000]", setup,
+                                 name="series_getitem_slice")
+
+
 #----------------------------------------------------------------------
 # DataFrame __getitem__