Fix flaky HashedRelationSuite

SparkEnv might not have been set in local unit tests.

Author: Reynold Xin <rxin@databricks.com>

Closes #7784 from rxin/HashedRelationSuite and squashes the following commits:

435d64b [Reynold Xin] Fix flaky HashedRelationSuite

sql/core/src/main/scala/org/apache/spark/sql/execution/joins/HashedRelation.scala

@@ -21,7 +21,7 @@ import java.io.{Externalizable, ObjectInput, ObjectOutput}
 import java.nio.ByteOrder
 import java.util.{HashMap => JavaHashMap}
 
-import org.apache.spark.{SparkEnv, TaskContext}
+import org.apache.spark.{SparkConf, SparkEnv, TaskContext}
 import org.apache.spark.sql.catalyst.InternalRow
 import org.apache.spark.sql.catalyst.expressions._
 import org.apache.spark.sql.execution.SparkSqlSerializer
@@ -260,7 +260,10 @@ private[joins] final class UnsafeHashedRelation(
     val nKeys = in.readInt()
     // This is used in Broadcast, shared by multiple tasks, so we use on-heap memory
     val memoryManager = new TaskMemoryManager(new ExecutorMemoryManager(MemoryAllocator.HEAP))
-    val pageSizeBytes = SparkEnv.get.conf.getSizeAsBytes("spark.buffer.pageSize", "64m")
+
+    val pageSizeBytes = Option(SparkEnv.get).map(_.conf).getOrElse(new SparkConf())
+      .getSizeAsBytes("spark.buffer.pageSize", "64m")
+
     binaryMap = new BytesToBytesMap(
       memoryManager,
       nKeys * 2, // reduce hash collision

sql/core/src/test/scala/org/apache/spark/sql/execution/joins/HashedRelationSuite.scala

@@ -33,7 +33,7 @@ class HashedRelationSuite extends SparkFunSuite {
     override def apply(row: InternalRow): InternalRow = row
   }
 
-  ignore("GeneralHashedRelation") {
+  test("GeneralHashedRelation") {
     val data = Array(InternalRow(0), InternalRow(1), InternalRow(2), InternalRow(2))
     val hashed = HashedRelation(data.iterator, keyProjection)
     assert(hashed.isInstanceOf[GeneralHashedRelation])
@@ -47,7 +47,7 @@ class HashedRelationSuite extends SparkFunSuite {
     assert(hashed.get(data(2)) === data2)
   }
 
-  ignore("UniqueKeyHashedRelation") {
+  test("UniqueKeyHashedRelation") {
     val data = Array(InternalRow(0), InternalRow(1), InternalRow(2))
     val hashed = HashedRelation(data.iterator, keyProjection)
     assert(hashed.isInstanceOf[UniqueKeyHashedRelation])
@@ -64,7 +64,7 @@ class HashedRelationSuite extends SparkFunSuite {
     assert(uniqHashed.getValue(InternalRow(10)) === null)
   }
 
-  ignore("UnsafeHashedRelation") {
+  test("UnsafeHashedRelation") {
     val schema = StructType(StructField("a", IntegerType, true) :: Nil)
     val data = Array(InternalRow(0), InternalRow(1), InternalRow(2), InternalRow(2))
     val toUnsafe = UnsafeProjection.create(schema)