[WIP][SPARK-27463][PYTHON] Support Dataframe Cogroup via Pandas UDFs

core/src/main/scala/org/apache/spark/api/python/PythonRunner.scala

@@ -47,6 +47,7 @@ private[spark] object PythonEvalType {
   val SQL_GROUPED_AGG_PANDAS_UDF = 202
   val SQL_WINDOW_AGG_PANDAS_UDF = 203
   val SQL_SCALAR_PANDAS_ITER_UDF = 204
+  val SQL_COGROUPED_MAP_PANDAS_UDF = 205
 
   def toString(pythonEvalType: Int): String = pythonEvalType match {
     case NON_UDF => "NON_UDF"
@@ -56,6 +57,7 @@ private[spark] object PythonEvalType {
     case SQL_GROUPED_AGG_PANDAS_UDF => "SQL_GROUPED_AGG_PANDAS_UDF"
     case SQL_WINDOW_AGG_PANDAS_UDF => "SQL_WINDOW_AGG_PANDAS_UDF"
     case SQL_SCALAR_PANDAS_ITER_UDF => "SQL_SCALAR_PANDAS_ITER_UDF"
+    case SQL_COGROUPED_MAP_PANDAS_UDF => "SQL_COGROUPED_MAP_PANDAS_UDF"
   }
 }
 

python/pyspark/rdd.py

@@ -74,6 +74,7 @@ class PythonEvalType(object):
     SQL_GROUPED_AGG_PANDAS_UDF = 202
     SQL_WINDOW_AGG_PANDAS_UDF = 203
     SQL_SCALAR_PANDAS_ITER_UDF = 204
+    SQL_COGROUPED_MAP_PANDAS_UDF = 205
 
 
 def portable_hash(x):

python/pyspark/serializers.py

@@ -356,6 +356,24 @@ def __repr__(self):
         return "ArrowStreamPandasSerializer"
 
 
+class InterleavedArrowReader(object):
+
+    def __init__(self, stream):
+        import pyarrow as pa
+        self._schema1 = pa.read_schema(stream)
+        self._schema2 = pa.read_schema(stream)
+        self._reader = pa.MessageReader.open_stream(stream)
+
+    def __iter__(self):
+        return self
+
+    def __next__(self):
+        import pyarrow as pa
+        batch1 = pa.read_record_batch(self._reader.read_next_message(),  self._schema1)
+        batch2 = pa.read_record_batch(self._reader.read_next_message(),  self._schema2)
+        return batch1, batch2
+
+
 class ArrowStreamPandasUDFSerializer(ArrowStreamPandasSerializer):
     """
     Serializer used by Python worker to evaluate Pandas UDFs
@@ -401,6 +419,22 @@ def __repr__(self):
         return "ArrowStreamPandasUDFSerializer"
 
 
+class InterleavedArrowStreamPandasSerializer(ArrowStreamPandasUDFSerializer):
+
+    def __init__(self, timezone, safecheck, assign_cols_by_name):
+        super(InterleavedArrowStreamPandasSerializer, self).__init__(timezone, safecheck, assign_cols_by_name)
+
+    def load_stream(self, stream):
+        """
+        Deserialize ArrowRecordBatches to an Arrow table and return as a list of pandas.Series.
+        """
+        import pyarrow as pa
+        reader = InterleavedArrowReader(pa.input_stream(stream))
+        for batch1, batch2 in reader:
+            yield ( [self.arrow_to_pandas(c) for c in pa.Table.from_batches([batch1]).itercolumns()],
+                    [self.arrow_to_pandas(c) for c in pa.Table.from_batches([batch2]).itercolumns()])
+
+
 class BatchedSerializer(Serializer):
 
     """

python/pyspark/sql/cogroup.py

@@ -0,0 +1,21 @@
+from pyspark.sql.dataframe import DataFrame
+
+
+class CoGroupedData(object):
+
+    def __init__(self, gd1, gd2):
+        self._gd1 = gd1
+        self._gd2 = gd2
+        self.sql_ctx = gd1.sql_ctx
+
+    def apply(self, udf):
+        all_cols = self._extract_cols(self._gd1) + self._extract_cols(self._gd2)
+        udf_column = udf(*all_cols)
+        jdf = self._gd1._jgd.flatMapCoGroupsInPandas(self._gd2._jgd, udf_column._jc.expr())
+        return DataFrame(jdf, self.sql_ctx)
+
+    @staticmethod
+    def _extract_cols(gd):
+        df = gd._df
+        return [df[col] for col in df.columns]
+

python/pyspark/sql/functions.py

@@ -2800,6 +2800,8 @@ class PandasUDFType(object):
 
     GROUPED_MAP = PythonEvalType.SQL_GROUPED_MAP_PANDAS_UDF
 
+    COGROUPED_MAP = PythonEvalType.SQL_COGROUPED_MAP_PANDAS_UDF
+
     GROUPED_AGG = PythonEvalType.SQL_GROUPED_AGG_PANDAS_UDF
 
 
@@ -3178,6 +3180,7 @@ def pandas_udf(f=None, returnType=None, functionType=None):
     if eval_type not in [PythonEvalType.SQL_SCALAR_PANDAS_UDF,
                          PythonEvalType.SQL_SCALAR_PANDAS_ITER_UDF,
                          PythonEvalType.SQL_GROUPED_MAP_PANDAS_UDF,
+                         PythonEvalType.SQL_COGROUPED_MAP_PANDAS_UDF,
                          PythonEvalType.SQL_GROUPED_AGG_PANDAS_UDF]:
         raise ValueError("Invalid functionType: "
                          "functionType must be one the values from PandasUDFType")

python/pyspark/sql/group.py

@@ -22,6 +22,7 @@
 from pyspark.sql.column import Column, _to_seq
 from pyspark.sql.dataframe import DataFrame
 from pyspark.sql.types import *
+from pyspark.sql.cogroup import CoGroupedData
 
 __all__ = ["GroupedData"]
 
@@ -220,6 +221,9 @@ def pivot(self, pivot_col, values=None):
             jgd = self._jgd.pivot(pivot_col, values)
         return GroupedData(jgd, self._df)
 
+    def cogroup(self, other):
+        return CoGroupedData(self, other)
+
     @since(2.3)
     def apply(self, udf):
         """

python/pyspark/sql/tests/test_pandas_udf_cogrouped_map.py

@@ -0,0 +1,93 @@
+#
+# Licensed to the Apache Software Foundation (ASF) under one or more
+# contributor license agreements.  See the NOTICE file distributed with
+# this work for additional information regarding copyright ownership.
+# The ASF licenses this file to You under the Apache License, Version 2.0
+# (the "License"); you may not use this file except in compliance with
+# the License.  You may obtain a copy of the License at
+#
+#    http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+#
+
+import datetime
+import unittest
+import sys
+
+from collections import OrderedDict
+from decimal import Decimal
+
+from pyspark.sql import Row
+from pyspark.sql.functions import array, explode, col, lit, udf, sum, pandas_udf, PandasUDFType
+from pyspark.sql.types import *
+from pyspark.testing.sqlutils import ReusedSQLTestCase, have_pandas, have_pyarrow, \
+    pandas_requirement_message, pyarrow_requirement_message
+from pyspark.testing.utils import QuietTest
+
+if have_pandas:
+    import pandas as pd
+    from pandas.util.testing import assert_frame_equal
+
+if have_pyarrow:
+    import pyarrow as pa
+
+
+"""
+Tests below use pd.DataFrame.assign that will infer mixed types (unicode/str) for column names
+from kwargs w/ Python 2, so need to set check_column_type=False and avoid this check
+"""
+if sys.version < '3':
+    _check_column_type = False
+else:
+    _check_column_type = True
+
+
+@unittest.skipIf(
+    not have_pandas or not have_pyarrow,
+    pandas_requirement_message or pyarrow_requirement_message)
+class CoGroupedMapPandasUDFTests(ReusedSQLTestCase):
+
+    @property
+    def data1(self):
+        return self.spark.range(10).toDF('id') \
+            .withColumn("ks", array([lit(i) for i in range(20, 30)])) \
+            .withColumn("k", explode(col('ks')))\
+            .withColumn("v", col('k') * 10)\
+            .drop('ks')
+
+    @property
+    def data2(self):
+        return self.spark.range(10).toDF('id') \
+            .withColumn("ks", array([lit(i) for i in range(20, 30)])) \
+            .withColumn("k", explode(col('ks'))) \
+            .withColumn("v2", col('k') * 100) \
+            .drop('ks')
+
+    def test_simple(self):
+        import pandas as pd
+
+        l = self.data1
+        r = self.data2
+
+        @pandas_udf('id long, k int, v int, v2 int', PandasUDFType.COGROUPED_MAP)
+        def merge_pandas(left, right):
+            return pd.merge(left, right, how='outer', on=['k', 'id'])
+
+        # TODO: Grouping by a string fails to resolve here as analyzer cannot determine side
+        result = l\
+            .groupby(l.id)\
+            .cogroup(r.groupby(r.id))\
+            .apply(merge_pandas)\
+            .sort(['id', 'k'])\
+            .toPandas()
+
+        expected = pd\
+            .merge(l.toPandas(), r.toPandas(), how='outer', on=['k', 'id'])
+
+        assert_frame_equal(expected, result, check_column_type=_check_column_type)
+

python/pyspark/worker.py

@@ -38,7 +38,7 @@
 from pyspark.rdd import PythonEvalType
 from pyspark.serializers import write_with_length, write_int, read_long, read_bool, \
     write_long, read_int, SpecialLengths, UTF8Deserializer, PickleSerializer, \
-    BatchedSerializer, ArrowStreamPandasUDFSerializer
+    BatchedSerializer, ArrowStreamPandasUDFSerializer, InterleavedArrowStreamPandasSerializer
 from pyspark.sql.types import to_arrow_type, StructType
 from pyspark.util import _get_argspec, fail_on_stopiteration
 from pyspark import shuffle
@@ -111,8 +111,25 @@ def verify_result_length(result, length):
                                      map(verify_result_type, f(*iterator)))
 
 
-def wrap_grouped_map_pandas_udf(f, return_type, argspec):
+def wrap_cogrouped_map_pandas_udf(f, return_type):
 
+    def wrapped(left, right):
+        import pandas as pd
+        result = f(pd.concat(left, axis=1), pd.concat(right, axis=1))
+        if not isinstance(result, pd.DataFrame):
+            raise TypeError("Return type of the user-defined function should be "
+                            "pandas.DataFrame, but is {}".format(type(result)))
+        if not len(result.columns) == len(return_type):
+            raise RuntimeError(
+                "Number of columns of the returned pandas.DataFrame "
+                "doesn't match specified schema. "
+                "Expected: {} Actual: {}".format(len(return_type), len(result.columns)))
+        return result
+
+    return lambda v: [(wrapped(v[0], v[1]), to_arrow_type(return_type))]
+
+
+def wrap_grouped_map_pandas_udf(f, return_type, argspec):
     def wrapped(key_series, value_series):
         import pandas as pd
 
@@ -232,6 +249,8 @@ def read_single_udf(pickleSer, infile, eval_type, runner_conf, udf_index):
     elif eval_type == PythonEvalType.SQL_GROUPED_MAP_PANDAS_UDF:
         argspec = _get_argspec(chained_func)  # signature was lost when wrapping it
         return arg_offsets, wrap_grouped_map_pandas_udf(func, return_type, argspec)
+    elif eval_type == PythonEvalType.SQL_COGROUPED_MAP_PANDAS_UDF:
+        return arg_offsets, wrap_cogrouped_map_pandas_udf(func, return_type)
     elif eval_type == PythonEvalType.SQL_GROUPED_AGG_PANDAS_UDF:
         return arg_offsets, wrap_grouped_agg_pandas_udf(func, return_type)
     elif eval_type == PythonEvalType.SQL_WINDOW_AGG_PANDAS_UDF:
@@ -246,6 +265,7 @@ def read_udfs(pickleSer, infile, eval_type):
     runner_conf = {}
 
     if eval_type in (PythonEvalType.SQL_SCALAR_PANDAS_UDF,
+                     PythonEvalType.SQL_COGROUPED_MAP_PANDAS_UDF,
                      PythonEvalType.SQL_SCALAR_PANDAS_ITER_UDF,
                      PythonEvalType.SQL_GROUPED_MAP_PANDAS_UDF,
                      PythonEvalType.SQL_GROUPED_AGG_PANDAS_UDF,
@@ -269,10 +289,13 @@ def read_udfs(pickleSer, infile, eval_type):
 
         # Scalar Pandas UDF handles struct type arguments as pandas DataFrames instead of
         # pandas Series. See SPARK-27240.
-        df_for_struct = (eval_type == PythonEvalType.SQL_SCALAR_PANDAS_UDF or
+        if eval_type == PythonEvalType.SQL_COGROUPED_MAP_PANDAS_UDF:
+            ser = InterleavedArrowStreamPandasSerializer(timezone, safecheck, assign_cols_by_name)
+        else:
+            df_for_struct = (eval_type == PythonEvalType.SQL_SCALAR_PANDAS_UDF or
                          eval_type == PythonEvalType.SQL_SCALAR_PANDAS_ITER_UDF)
-        ser = ArrowStreamPandasUDFSerializer(timezone, safecheck, assign_cols_by_name,
-                                             df_for_struct)
+            ser = ArrowStreamPandasUDFSerializer(timezone, safecheck, assign_cols_by_name,
+                                                 df_for_struct)
     else:
         ser = BatchedSerializer(PickleSerializer(), 100)
 
@@ -343,6 +366,14 @@ def map_batch(batch):
         arg0 = ["a[%d]" % o for o in arg_offsets[1: split_offset]]
         arg1 = ["a[%d]" % o for o in arg_offsets[split_offset:]]
         mapper_str = "lambda a: f([%s], [%s])" % (", ".join(arg0), ", ".join(arg1))
+    elif eval_type == PythonEvalType.SQL_COGROUPED_MAP_PANDAS_UDF:
+        # We assume there is only one UDF here because cogrouped map doesn't
+        # support combining multiple UDFs.
+        assert num_udfs == 1
+        arg_offsets, udf = read_single_udf(
+            pickleSer, infile, eval_type, runner_conf, udf_index=0)
+        udfs['f'] = udf
+        mapper_str = "lambda a: f(a)"
     else:
         # Create function like this:
         #   lambda a: (f0(a[0]), f1(a[1], a[2]), f2(a[3]))

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/plans/logical/pythonLogicalOperators.scala

@@ -39,6 +39,18 @@ case class FlatMapGroupsInPandas(
   override val producedAttributes = AttributeSet(output)
 }
 
+
+case class FlatMapCoGroupsInPandas(
+                                  leftAttributes: Seq[Attribute],
+                                  rightAttributes: Seq[Attribute],
+                                  functionExpr: Expression,
+                                  output: Seq[Attribute],
+                                  left: LogicalPlan,
+                                  right: LogicalPlan) extends BinaryNode {
+  override val producedAttributes = AttributeSet(output)
+}
+
+
 trait BaseEvalPython extends UnaryNode {
 
   def udfs: Seq[PythonUDF]

sql/core/src/main/scala/org/apache/spark/sql/RelationalGroupedDataset.scala

@@ -47,8 +47,8 @@ import org.apache.spark.sql.types.{NumericType, StructType}
  */
 @Stable
 class RelationalGroupedDataset protected[sql](
-    df: DataFrame,
-    groupingExprs: Seq[Expression],
+    private val df: DataFrame,
+    private val groupingExprs: Seq[Expression],
     groupType: RelationalGroupedDataset.GroupType) {
 
   private[this] def toDF(aggExprs: Seq[Expression]): DataFrame = {
@@ -523,6 +523,33 @@ class RelationalGroupedDataset protected[sql](
     Dataset.ofRows(df.sparkSession, plan)
   }
 
+  private[sql] def flatMapCoGroupsInPandas
+  (r: RelationalGroupedDataset, expr: PythonUDF): DataFrame = {
+    require(expr.evalType == PythonEvalType.SQL_COGROUPED_MAP_PANDAS_UDF,
+      "Must pass a cogrouped map udf")
+    require(expr.dataType.isInstanceOf[StructType],
+      s"The returnType of the udf must be a ${StructType.simpleString}")
+
+    val leftGroupingNamedExpressions = groupingExprs.map {
+      case ne: NamedExpression => ne
+      case other => Alias(other, other.toString)()
+    }
+
+    val rightGroupingNamedExpressions = r.groupingExprs.map {
+      case ne: NamedExpression => ne
+      case other => Alias(other, other.toString)()
+    }
+
+    val leftAttributes = leftGroupingNamedExpressions.map(_.toAttribute)
+    val rightAttributes = rightGroupingNamedExpressions.map(_.toAttribute)
+    val left = df.logicalPlan
+    val right = r.df.logicalPlan
+    val output = expr.dataType.asInstanceOf[StructType].toAttributes
+    val plan = FlatMapCoGroupsInPandas(leftAttributes, rightAttributes, expr, output, left, right)
+
+    Dataset.ofRows(df.sparkSession, plan)
+  }
+
   override def toString: String = {
     val builder = new StringBuilder
     builder.append("RelationalGroupedDataset: [grouping expressions: [")

sql/core/src/main/scala/org/apache/spark/sql/execution/SparkStrategies.scala

@@ -682,6 +682,9 @@ abstract class SparkStrategies extends QueryPlanner[SparkPlan] {
           f, p, b, is, ot, planLater(child)) :: Nil
       case logical.FlatMapGroupsInPandas(grouping, func, output, child) =>
         execution.python.FlatMapGroupsInPandasExec(grouping, func, output, planLater(child)) :: Nil
+      case logical.FlatMapCoGroupsInPandas(leftGroup, rightGroup, func, output, left, right) =>
+        execution.python.FlatMapCoGroupsInPandasExec(
+          leftGroup, rightGroup, func, output, planLater(left), planLater(right)) :: Nil
       case logical.MapElements(f, _, _, objAttr, child) =>
         execution.MapElementsExec(f, objAttr, planLater(child)) :: Nil
       case logical.AppendColumns(f, _, _, in, out, child) =>