[SPARK-5579][SQL][DataFrame] Support for project/filter using SQL expressions

```scala
df.selectExpr("abs(colA)", "colB")
df.filter("age > 21")
```

Author: Reynold Xin <rxin@databricks.com>

Closes #4348 from rxin/SPARK-5579 and squashes the following commits:

2baeef2 [Reynold Xin] Fix Python.
b416372 [Reynold Xin] [SPARK-5579][SQL][DataFrame] Support for project/filter using SQL expressions.

1 files changed, 12 insertions, 0 deletions

diff --git a/sql/core/src/test/scala/org/apache/spark/sql/DataFrameSuite.scala b/sql/core/src/test/scala/org/apache/spark/sql/DataFrameSuite.scala
index 19d4f34e56..e588555ad0 100644
--- a/sql/core/src/test/scala/org/apache/spark/sql/DataFrameSuite.scala
+++ b/sql/core/src/test/scala/org/apache/spark/sql/DataFrameSuite.scala
@@ -47,6 +47,18 @@ class DataFrameSuite extends QueryTest {
       testData.collect().toSeq)
   }
 
+  test("selectExpr") {
+    checkAnswer(
+      testData.selectExpr("abs(key)", "value"),
+      testData.collect().map(row => Row(math.abs(row.getInt(0)), row.getString(1))).toSeq)
+  }
+
+  test("filterExpr") {
+    checkAnswer(
+      testData.filter("key > 90"),
+      testData.collect().filter(_.getInt(0) > 90).toSeq)
+  }
+
   test("repartition") {
     checkAnswer(
       testData.select('key).repartition(10).select('key),