FIX-#1976: indices matching at reduction functions fixed

modin/backends/pandas/query_compiler.py

@@ -22,12 +22,15 @@
     is_scalar,
 )
 from pandas.core.base import DataError
+from typing import Type, Callable
 import warnings
 
+
 from modin.backends.base.query_compiler import BaseQueryCompiler
 from modin.error_message import ErrorMessage
 from modin.utils import try_cast_to_pandas, wrap_udf_function
 from modin.data_management.functions import (
+    Function,
     FoldFunction,
     MapFunction,
     MapReduceFunction,
@@ -150,6 +153,32 @@ def caller(df, *args, **kwargs):
     return caller
 
 
+def _numeric_only_reduce_fn(applier: Type[Function], *funcs) -> Callable:
+    """
+    Build reduce function for statistic operations with `numeric_only` parameter.
+
+    Parameters
+    ----------
+    applier : Function object to register `funcs`
+    *funcs : list of functions to register in `applier`
+
+    Returns
+    -------
+    callable
+        A callable function to be applied in the partitions
+    """
+
+    def caller(self, *args, **kwargs):
+        # If `numeric_only` is None then we don't know what columns/indices will
+        # be dropped at the result of reduction function, and so can't preserve labels
+        preserve_index = kwargs.get("numeric_only", None) is not None
+        return applier.register(*funcs, preserve_index=preserve_index)(
+            self, *args, **kwargs
+        )
+
+    return caller
+
+
 class PandasQueryCompiler(BaseQueryCompiler):
     """This class implements the logic necessary for operating on partitions
     with a Pandas backend. This logic is specific to Pandas."""
@@ -625,10 +654,10 @@ def is_monotonic_decreasing(self):
     is_monotonic = _is_monotonic
 
     count = MapReduceFunction.register(pandas.DataFrame.count, pandas.DataFrame.sum)
-    max = MapReduceFunction.register(pandas.DataFrame.max, pandas.DataFrame.max)
-    min = MapReduceFunction.register(pandas.DataFrame.min, pandas.DataFrame.min)
-    sum = MapReduceFunction.register(pandas.DataFrame.sum, pandas.DataFrame.sum)
-    prod = MapReduceFunction.register(pandas.DataFrame.prod, pandas.DataFrame.prod)
+    max = _numeric_only_reduce_fn(MapReduceFunction, pandas.DataFrame.max)
+    min = _numeric_only_reduce_fn(MapReduceFunction, pandas.DataFrame.min)
+    sum = _numeric_only_reduce_fn(MapReduceFunction, pandas.DataFrame.sum)
+    prod = _numeric_only_reduce_fn(MapReduceFunction, pandas.DataFrame.prod)
     any = MapReduceFunction.register(pandas.DataFrame.any, pandas.DataFrame.any)
     all = MapReduceFunction.register(pandas.DataFrame.all, pandas.DataFrame.all)
     memory_usage = MapReduceFunction.register(
@@ -664,7 +693,7 @@ def value_counts(self, **kwargs):
             return self.__constructor__(new_modin_frame)
 
         def map_func(df, *args, **kwargs):
-            return df.squeeze(axis=1).value_counts(**kwargs)
+            return df.squeeze(axis=1).value_counts(**kwargs).to_frame()
 
         def reduce_func(df, *args, **kwargs):
             normalize = kwargs.get("normalize", False)
@@ -735,28 +764,30 @@ def sort_index_for_equal_values(result, ascending):
                     else:
                         new_index[j] = result.index[j]
                     i += 1
-                return pandas.DataFrame(result, index=new_index)
+                return pandas.DataFrame(
+                    result, index=new_index, columns=["__reduced__"]
+                )
 
             return sort_index_for_equal_values(result, ascending)
 
-        return MapReduceFunction.register(map_func, reduce_func, preserve_index=False)(
-            self, **kwargs
-        )
+        return MapReduceFunction.register(
+            map_func, reduce_func, axis=0, preserve_index=False
+        )(self, **kwargs)
 
     # END MapReduce operations
 
     # Reduction operations
     idxmax = ReductionFunction.register(pandas.DataFrame.idxmax)
     idxmin = ReductionFunction.register(pandas.DataFrame.idxmin)
-    median = ReductionFunction.register(pandas.DataFrame.median)
+    median = _numeric_only_reduce_fn(ReductionFunction, pandas.DataFrame.median)
     nunique = ReductionFunction.register(pandas.DataFrame.nunique)
-    skew = ReductionFunction.register(pandas.DataFrame.skew)
-    kurt = ReductionFunction.register(pandas.DataFrame.kurt)
-    sem = ReductionFunction.register(pandas.DataFrame.sem)
-    std = ReductionFunction.register(pandas.DataFrame.std)
-    var = ReductionFunction.register(pandas.DataFrame.var)
-    sum_min_count = ReductionFunction.register(pandas.DataFrame.sum)
-    prod_min_count = ReductionFunction.register(pandas.DataFrame.prod)
+    skew = _numeric_only_reduce_fn(ReductionFunction, pandas.DataFrame.skew)
+    kurt = _numeric_only_reduce_fn(ReductionFunction, pandas.DataFrame.kurt)
+    sem = _numeric_only_reduce_fn(ReductionFunction, pandas.DataFrame.sem)
+    std = _numeric_only_reduce_fn(ReductionFunction, pandas.DataFrame.std)
+    var = _numeric_only_reduce_fn(ReductionFunction, pandas.DataFrame.var)
+    sum_min_count = _numeric_only_reduce_fn(ReductionFunction, pandas.DataFrame.sum)
+    prod_min_count = _numeric_only_reduce_fn(ReductionFunction, pandas.DataFrame.prod)
     quantile_for_single_value = ReductionFunction.register(pandas.DataFrame.quantile)
     mad = ReductionFunction.register(pandas.DataFrame.mad)
     to_datetime = ReductionFunction.register(

modin/data_management/functions/__init__.py

@@ -11,6 +11,7 @@
 # ANY KIND, either express or implied. See the License for the specific language
 # governing permissions and limitations under the License.
 
+from .function import Function
 from .mapfunction import MapFunction
 from .mapreducefunction import MapReduceFunction
 from .reductionfunction import ReductionFunction
@@ -19,6 +20,7 @@
 from .groupby_function import GroupbyReduceFunction
 
 __all__ = [
+    "Function",
     "MapFunction",
     "MapReduceFunction",
     "ReductionFunction",

modin/data_management/functions/foldfunction.py

@@ -18,11 +18,10 @@ class FoldFunction(Function):
     @classmethod
     def call(cls, fold_function, **call_kwds):
         def caller(query_compiler, *args, **kwargs):
+            axis = call_kwds.get("axis") if "axis" in call_kwds else kwargs.get("axis")
             return query_compiler.__constructor__(
                 query_compiler._modin_frame._fold(
-                    call_kwds.get("axis")
-                    if "axis" in call_kwds
-                    else kwargs.get("axis"),
+                    cls.validate_axis(axis),
                     lambda x: fold_function(x, *args, **kwargs),
                 )
             )

modin/data_management/functions/function.py

@@ -11,6 +11,8 @@
 # ANY KIND, either express or implied. See the License for the specific language
 # governing permissions and limitations under the License.
 
+from typing import Optional
+
 
 class Function(object):
     def __init__(self):
@@ -27,3 +29,7 @@ def call(cls, func, **call_kwds):
     @classmethod
     def register(cls, func, **kwargs):
         return cls.call(func, **kwargs)
+
+    @classmethod
+    def validate_axis(cls, axis: Optional[int]) -> int:
+        return 0 if axis is None else axis

modin/data_management/functions/mapreducefunction.py

@@ -19,11 +19,10 @@ class MapReduceFunction(Function):
     def call(cls, map_function, reduce_function, **call_kwds):
         def caller(query_compiler, *args, **kwargs):
             preserve_index = call_kwds.pop("preserve_index", True)
+            axis = call_kwds.get("axis") if "axis" in call_kwds else kwargs.get("axis")
             return query_compiler.__constructor__(
                 query_compiler._modin_frame._map_reduce(
-                    call_kwds.get("axis")
-                    if "axis" in call_kwds
-                    else kwargs.get("axis"),
+                    cls.validate_axis(axis),
                     lambda x: map_function(x, *args, **kwargs),
                     lambda y: reduce_function(y, *args, **kwargs),
                     preserve_index=preserve_index,
@@ -33,5 +32,7 @@ def caller(query_compiler, *args, **kwargs):
         return caller
 
     @classmethod
-    def register(cls, map_function, reduce_function, **kwargs):
+    def register(cls, map_function, reduce_function=None, **kwargs):
+        if reduce_function is None:
+            reduce_function = map_function
         return cls.call(map_function, reduce_function, **kwargs)

modin/data_management/functions/reductionfunction.py

@@ -18,12 +18,13 @@ class ReductionFunction(Function):
     @classmethod
     def call(cls, reduction_function, **call_kwds):
         def caller(query_compiler, *args, **kwargs):
+            preserve_index = call_kwds.pop("preserve_index", True)
+            axis = call_kwds.get("axis") if "axis" in call_kwds else kwargs.get("axis")
             return query_compiler.__constructor__(
                 query_compiler._modin_frame._fold_reduce(
-                    call_kwds.get("axis")
-                    if "axis" in call_kwds
-                    else kwargs.get("axis"),
+                    cls.validate_axis(axis),
                     lambda x: reduction_function(x, *args, **kwargs),
+                    preserve_index=preserve_index,
                 )
             )