SPARK-2186: Spark SQL DSL support for simple aggregations such as SUM and AVG

Author: Ximo Guanter Gonzalbez

sql/core/src/main/scala/org/apache/spark/sql/SchemaRDD.scala

@@ -133,8 +133,13 @@ class SchemaRDD(
    *
    * @group Query
    */
-  def select(exprs: NamedExpression*): SchemaRDD =
-    new SchemaRDD(sqlContext, Project(exprs, logicalPlan))
+  def select(exprs: Expression*): SchemaRDD = {
+    val aliases = exprs.zipWithIndex.map {
+      case (ne: NamedExpression, _) => ne
+      case (e, i) => Alias(e, s"c$i")()
+    }
+    new SchemaRDD(sqlContext, Project(aliases, logicalPlan))
+  }
 
   /**
    * Filters the output, only returning those rows where `condition` evaluates to true.

sql/core/src/test/scala/org/apache/spark/sql/DslQuerySuite.scala

@@ -61,6 +61,30 @@ class DslQuerySuite extends QueryTest {
       Seq(Seq("1")))
   }
 
+  test("select with functions") {
+    checkAnswer(
+      testData.select(Sum('value)),
+      Seq(Seq(5050.0)))
+
+    checkAnswer(
+      testData.select(Average('value)),
+      Seq(Seq(50.5)))
+
+    checkAnswer(
+      testData.select(Count(1)),
+      Seq(Seq(100)))
+
+    checkAnswer(
+      testData2.select('a + 'b, 'a < 'b),
+      Seq(
+        Seq(2, false),
+        Seq(3, true),
+        Seq(3, false),
+        Seq(4, false),
+        Seq(4, false),
+        Seq(5, false)))
+  }
+
   test("sorting") {
     checkAnswer(
       testData2.orderBy('a.asc, 'b.asc),