[SPARK-7548] [SQL] Add explode function for DataFrames

Add an `explode` function for dataframes and modify the analyzer so that single table generating functions can be present in a select clause along with other expressions.   There are currently the following restrictions:
 - only top level TGFs are allowed (i.e. no `select(explode('list) + 1)`)
 - only one may be present in a single select to avoid potentially confusing implicit Cartesian products.

TODO:
 - [ ] Python

Author: Michael Armbrust <michael@databricks.com>

Closes #6107 from marmbrus/explodeFunction and squashes the following commits:

7ee2c87 [Michael Armbrust] whitespace
6f80ba3 [Michael Armbrust] Update dataframe.py
c176c89 [Michael Armbrust] Merge remote-tracking branch 'origin/master' into explodeFunction
81b5da3 [Michael Armbrust] style
d3faa05 [Michael Armbrust] fix self join case
f9e1e3e [Michael Armbrust] fix python, add since
4f0d0a9 [Michael Armbrust] Merge remote-tracking branch 'origin/master' into explodeFunction
e710fe4 [Michael Armbrust] add java and python
52ca0dc [Michael Armbrust] [SPARK-7548][SQL] Add explode function for dataframes.

1 files changed, 15 insertions, 0 deletions

diff --git a/python/pyspark/sql/tests.py b/python/pyspark/sql/tests.py
index 1922d03af6..d37c5dbed7 100644
--- a/python/pyspark/sql/tests.py
+++ b/python/pyspark/sql/tests.py
@@ -117,6 +117,21 @@ class SQLTests(ReusedPySparkTestCase):
         ReusedPySparkTestCase.tearDownClass()
         shutil.rmtree(cls.tempdir.name, ignore_errors=True)
 
+    def test_explode(self):
+        from pyspark.sql.functions import explode
+        d = [Row(a=1, intlist=[1, 2, 3], mapfield={"a": "b"})]
+        rdd = self.sc.parallelize(d)
+        data = self.sqlCtx.createDataFrame(rdd)
+
+        result = data.select(explode(data.intlist).alias("a")).select("a").collect()
+        self.assertEqual(result[0][0], 1)
+        self.assertEqual(result[1][0], 2)
+        self.assertEqual(result[2][0], 3)
+
+        result = data.select(explode(data.mapfield).alias("a", "b")).select("a", "b").collect()
+        self.assertEqual(result[0][0], "a")
+        self.assertEqual(result[0][1], "b")
+
     def test_udf_with_callable(self):
         d = [Row(number=i, squared=i**2) for i in range(10)]
         rdd = self.sc.parallelize(d)