[SPARK-2729][SQL] Added test case for SPARK-2729

This is a follow up of #1636.

Author: Cheng Lian <lian.cs.zju@gmail.com>

Closes #1738 from liancheng/test-for-spark-2729 and squashes the following commits:

b13692a [Cheng Lian] Added test case for SPARK-2729

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

@@ -17,11 +17,13 @@
 
 package org.apache.spark.sql
 
+import java.sql.Timestamp
+
 import org.apache.spark.sql.catalyst.plans.logical
 import org.apache.spark.sql.test._
 
 /* Implicits */
-import TestSQLContext._
+import org.apache.spark.sql.test.TestSQLContext._
 
 case class TestData(key: Int, value: String)
 
@@ -40,7 +42,7 @@ object TestData {
       LargeAndSmallInts(2147483646, 1) ::
       LargeAndSmallInts(3, 2) :: Nil)
   largeAndSmallInts.registerAsTable("largeAndSmallInts")
-  
+
   case class TestData2(a: Int, b: Int)
   val testData2: SchemaRDD =
     TestSQLContext.sparkContext.parallelize(
@@ -143,4 +145,10 @@ object TestData {
       "2, B2, false, null" ::
       "3, C3, true, null" ::
       "4, D4, true, 2147483644" :: Nil)
+
+  case class TimestampField(time: Timestamp)
+  val timestamps = TestSQLContext.sparkContext.parallelize((1 to 3).map { i =>
+    TimestampField(new Timestamp(i))
+  })
+  timestamps.registerAsTable("timestamps")
 }

sql/core/src/test/scala/org/apache/spark/sql/columnar/InMemoryColumnarQuerySuite.scala

@@ -73,4 +73,16 @@ class InMemoryColumnarQuerySuite extends QueryTest {
       sql("SELECT * FROM nullableRepeatedData"),
       nullableRepeatedData.collect().toSeq)
   }
+
+  test("SPARK-2729 regression: timestamp data type") {
+    checkAnswer(
+      sql("SELECT time FROM timestamps"),
+      timestamps.collect().toSeq)
+
+    TestSQLContext.cacheTable("timestamps")
+
+    checkAnswer(
+      sql("SELECT time FROM timestamps"),
+      timestamps.collect().toSeq)
+  }
 }