[SPARK-5859] [PySpark] [SQL] fix DataFrame Python API

1. added explain()
2. add isLocal()
3. do not call show() in __repl__
4. add foreach() and foreachPartition()
5. add distinct()
6. fix functions.col()/column()/lit()
7. fix unit tests in sql/functions.py
8. fix unicode in showString()

Author: Davies Liu <davies@databricks.com>

Closes #4645 from davies/df6 and squashes the following commits:

6b46a2c [Davies Liu] fix DataFrame Python API

python/pyspark/sql/dataframe.py

@@ -238,6 +238,22 @@ def printSchema(self):
         """
         print (self._jdf.schema().treeString())
 
+    def explain(self, extended=False):
+        """
+        Prints the plans (logical and physical) to the console for
+        debugging purpose.
+
+        If extended is False, only prints the physical plan.
+        """
+        self._jdf.explain(extended)
+
+    def isLocal(self):
+        """
+        Returns True if the `collect` and `take` methods can be run locally
+        (without any Spark executors).
+        """
+        return self._jdf.isLocal()
+
     def show(self):
         """
         Print the first 20 rows.
@@ -247,14 +263,12 @@ def show(self):
         2   Alice
         5   Bob
         >>> df
-        age name
-        2   Alice
-        5   Bob
+        DataFrame[age: int, name: string]
         """
-        print (self)
+        print self._jdf.showString().encode('utf8', 'ignore')
 
     def __repr__(self):
-        return self._jdf.showString()
+        return "DataFrame[%s]" % (", ".join("%s: %s" % c for c in self.dtypes))
 
     def count(self):
         """Return the number of elements in this RDD.
@@ -336,13 +350,40 @@ def mapPartitions(self, f, preservesPartitioning=False):
         """
         Return a new RDD by applying a function to each partition.
 
+        It's a shorthand for df.rdd.mapPartitions()
+
         >>> rdd = sc.parallelize([1, 2, 3, 4], 4)
         >>> def f(iterator): yield 1
         >>> rdd.mapPartitions(f).sum()
         4
         """
         return self.rdd.mapPartitions(f, preservesPartitioning)
 
+    def foreach(self, f):
+        """
+        Applies a function to all rows of this DataFrame.
+
+        It's a shorthand for df.rdd.foreach()
+
+        >>> def f(person):
+        ...     print person.name
+        >>> df.foreach(f)
+        """
+        return self.rdd.foreach(f)
+
+    def foreachPartition(self, f):
+        """
+        Applies a function to each partition of this DataFrame.
+
+        It's a shorthand for df.rdd.foreachPartition()
+
+        >>> def f(people):
+        ...     for person in people:
+        ...         print person.name
+        >>> df.foreachPartition(f)
+        """
+        return self.rdd.foreachPartition(f)
+
     def cache(self):
         """ Persist with the default storage level (C{MEMORY_ONLY_SER}).
         """
@@ -377,8 +418,13 @@ def repartition(self, numPartitions):
         """ Return a new :class:`DataFrame` that has exactly `numPartitions`
         partitions.
         """
-        rdd = self._jdf.repartition(numPartitions, None)
-        return DataFrame(rdd, self.sql_ctx)
+        return DataFrame(self._jdf.repartition(numPartitions, None), self.sql_ctx)
+
+    def distinct(self):
+        """
+        Return a new :class:`DataFrame` containing the distinct rows in this DataFrame.
+        """
+        return DataFrame(self._jdf.distinct(), self.sql_ctx)
 
     def sample(self, withReplacement, fraction, seed=None):
         """
@@ -957,10 +1003,7 @@ def cast(self, dataType):
         return Column(jc, self.sql_ctx)
 
     def __repr__(self):
-        if self._jdf.isComputable():
-            return self._jdf.samples()
-        else:
-            return 'Column<%s>' % self._jdf.toString()
+        return 'Column<%s>' % self._jdf.toString().encode('utf8')
 
     def toPandas(self):
         """

python/pyspark/sql/functions.py

@@ -37,7 +37,7 @@ def _create_function(name, doc=""):
     """ Create a function for aggregator by name"""
     def _(col):
         sc = SparkContext._active_spark_context
-        jc = getattr(sc._jvm.functions, name)(_to_java_column(col))
+        jc = getattr(sc._jvm.functions, name)(col._jc if isinstance(col, Column) else col)
         return Column(jc)
     _.__name__ = name
     _.__doc__ = doc
@@ -140,6 +140,7 @@ def __call__(self, *cols):
 def udf(f, returnType=StringType()):
     """Create a user defined function (UDF)
 
+    >>> from pyspark.sql.types import IntegerType
     >>> slen = udf(lambda s: len(s), IntegerType())
     >>> df.select(slen(df.name).alias('slen')).collect()
     [Row(slen=5), Row(slen=3)]
@@ -151,17 +152,14 @@ def _test():
     import doctest
     from pyspark.context import SparkContext
     from pyspark.sql import Row, SQLContext
-    import pyspark.sql.dataframe
-    globs = pyspark.sql.dataframe.__dict__.copy()
+    import pyspark.sql.functions
+    globs = pyspark.sql.functions.__dict__.copy()
     sc = SparkContext('local[4]', 'PythonTest')
     globs['sc'] = sc
     globs['sqlCtx'] = SQLContext(sc)
     globs['df'] = sc.parallelize([Row(name='Alice', age=2), Row(name='Bob', age=5)]).toDF()
-    globs['df2'] = sc.parallelize([Row(name='Tom', height=80), Row(name='Bob', height=85)]).toDF()
-    globs['df3'] = sc.parallelize([Row(name='Alice', age=2, height=80),
-                                  Row(name='Bob', age=5, height=85)]).toDF()
     (failure_count, test_count) = doctest.testmod(
-        pyspark.sql.dataframe, globs=globs,
+        pyspark.sql.functions, globs=globs,
         optionflags=doctest.ELLIPSIS | doctest.NORMALIZE_WHITESPACE)
     globs['sc'].stop()
     if failure_count: