[SPARK-7059][SQL] Create a DataFrame join API to facilitate equijoin.

Author: Reynold Xin <rxin@databricks.com>

Closes #5638 from rxin/joinUsing and squashes the following commits:

13e9cc9 [Reynold Xin] Code review + Python.
b1bd914 [Reynold Xin] [SPARK-7059][SQL] Create a DataFrame join API to facilitate equijoin and self join.

1 files changed, 8 insertions, 1 deletions

diff --git a/python/pyspark/sql/dataframe.py b/python/pyspark/sql/dataframe.py
index ca9bf8efb9..c8c30ce402 100644
--- a/python/pyspark/sql/dataframe.py
+++ b/python/pyspark/sql/dataframe.py
@@ -459,16 +459,23 @@ class DataFrame(object):
         The following performs a full outer join between ``df1`` and ``df2``.
 
         :param other: Right side of the join
-        :param joinExprs: Join expression
+        :param joinExprs: a string for join column name, or a join expression (Column).
+            If joinExprs is a string indicating the name of the join column,
+            the column must exist on both sides, and this performs an inner equi-join.
         :param joinType: str, default 'inner'.
             One of `inner`, `outer`, `left_outer`, `right_outer`, `semijoin`.
 
         >>> df.join(df2, df.name == df2.name, 'outer').select(df.name, df2.height).collect()
         [Row(name=None, height=80), Row(name=u'Alice', height=None), Row(name=u'Bob', height=85)]
+
+        >>> df.join(df2, 'name').select(df.name, df2.height).collect()
+        [Row(name=u'Bob', height=85)]
         """
 
         if joinExprs is None:
             jdf = self._jdf.join(other._jdf)
+        elif isinstance(joinExprs, basestring):
+            jdf = self._jdf.join(other._jdf, joinExprs)
         else:
             assert isinstance(joinExprs, Column), "joinExprs should be Column"
             if joinType is None: