[SPARK-19429][PYTHON][SQL] Support slice arguments in Column.__getitem__

## What changes were proposed in this pull request?

- Add support for `slice` arguments in `Column.__getitem__`.
- Remove obsolete `__getslice__` bindings.

## How was this patch tested?

Existing unit tests, additional tests covering `[]` with `slice`.

Author: zero323 <zero323@users.noreply.github.com>

Closes #16771 from zero323/SPARK-19429.

2 files changed, 16 insertions, 3 deletions

diff --git a/python/pyspark/sql/column.py b/python/pyspark/sql/column.py
index ec059d6258..73c8672eff 100644
--- a/python/pyspark/sql/column.py
+++ b/python/pyspark/sql/column.py
@@ -180,7 +180,6 @@ class Column(object):
 
     # container operators
     __contains__ = _bin_op("contains")
-    __getitem__ = _bin_op("apply")
 
     # bitwise operators
     bitwiseOR = _bin_op("bitwiseOR")
@@ -236,6 +235,14 @@ class Column(object):
             raise AttributeError(item)
         return self.getField(item)
 
+    def __getitem__(self, k):
+        if isinstance(k, slice):
+            if k.step is not None:
+                raise ValueError("slice with step is not supported.")
+            return self.substr(k.start, k.stop)
+        else:
+            return _bin_op("apply")(self, k)
+
     def __iter__(self):
         raise TypeError("Column is not iterable")
 
@@ -267,8 +274,6 @@ class Column(object):
             raise TypeError("Unexpected type: %s" % type(startPos))
         return Column(jc)
 
-    __getslice__ = substr
-
     @ignore_unicode_prefix
     @since(1.5)
     def isin(self, *cols):
diff --git a/python/pyspark/sql/tests.py b/python/pyspark/sql/tests.py
index ab9d3f6c94..d9d03337ff 100644
--- a/python/pyspark/sql/tests.py
+++ b/python/pyspark/sql/tests.py
@@ -874,6 +874,14 @@ class SQLTests(ReusedPySparkTestCase):
         self.assertTrue(all(isinstance(c, Column) for c in css))
         self.assertTrue(isinstance(ci.cast(LongType()), Column))
 
+    def test_column_getitem(self):
+        from pyspark.sql.functions import col
+
+        self.assertIsInstance(col("foo")[1:3], Column)
+        self.assertIsInstance(col("foo")[0], Column)
+        self.assertIsInstance(col("foo")["bar"], Column)
+        self.assertRaises(ValueError, lambda: col("foo")[0:10:2])
+
     def test_column_select(self):
         df = self.df
         self.assertEqual(self.testData, df.select("*").collect())