[SPARK-13749][SQL][FOLLOW-UP] Faster pivot implementation for many distinct...

[SPARK-13749][SQL][FOLLOW-UP] Faster pivot implementation for many distinct values with two phase aggregation

## What changes were proposed in this pull request?

This is a follow up PR for #11583. It makes 3 lazy vals into just vals and adds unit test coverage.

## How was this patch tested?

Existing unit tests and additional unit tests.

Author: Andrew Ray <ray.andrew@gmail.com>

Closes #12861 from aray/fast-pivot-follow-up.

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/aggregate/PivotFirst.scala

@@ -141,12 +141,12 @@ case class PivotFirst(
     copy(mutableAggBufferOffset = newMutableAggBufferOffset)
 
 
-  override lazy val aggBufferAttributes: Seq[AttributeReference] =
+  override val aggBufferAttributes: Seq[AttributeReference] =
     pivotIndex.toList.sortBy(_._2).map(kv => AttributeReference(kv._1.toString, valueDataType)())
 
-  override lazy val aggBufferSchema: StructType = StructType.fromAttributes(aggBufferAttributes)
+  override val aggBufferSchema: StructType = StructType.fromAttributes(aggBufferAttributes)
 
-  override lazy val inputAggBufferAttributes: Seq[AttributeReference] =
+  override val inputAggBufferAttributes: Seq[AttributeReference] =
     aggBufferAttributes.map(_.newInstance())
 }
 

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

@@ -180,4 +180,21 @@ class DataFramePivotSuite extends QueryTest with SharedSQLContext{
     )
   }
 
+  test("pivot with datatype not supported by PivotFirst") {
+    checkAnswer(
+      complexData.groupBy().pivot("b", Seq(true, false)).agg(max("a")),
+      Row(Seq(1, 1, 1), Seq(2, 2, 2)) :: Nil
+    )
+  }
+
+  test("pivot with datatype not supported by PivotFirst 2") {
+    checkAnswer(
+      courseSales.withColumn("e", expr("array(earnings, 7.0d)"))
+        .groupBy("year")
+        .pivot("course", Seq("dotNET", "Java"))
+        .agg(min($"e")),
+      Row(2012, Seq(5000.0, 7.0), Seq(20000.0, 7.0)) ::
+        Row(2013, Seq(48000.0, 7.0), Seq(30000.0, 7.0)) :: Nil
+    )
+  }
 }