Spark-24742: Fix NullPointerexception in Field Metadata

sql/catalyst/src/main/scala/org/apache/spark/sql/types/Metadata.scala

@@ -215,6 +215,8 @@ object Metadata {
         x.##
       case x: Metadata =>
         hash(x.map)
+      case null =>
+        0
       case other =>
         throw new RuntimeException(s"Do not support type ${other.getClass}.")
     }

sql/catalyst/src/test/scala/org/apache/spark/sql/types/MetadataSuite.scala

@@ -0,0 +1,74 @@
+/*
+ * Licensed to the Apache Software Foundation (ASF) under one or more
+ * contributor license agreements.  See the NOTICE file distributed with
+ * this work for additional information regarding copyright ownership.
+ * The ASF licenses this file to You under the Apache License, Version 2.0
+ * (the "License"); you may not use this file except in compliance with
+ * the License.  You may obtain a copy of the License at
+ *
+ *    http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+package org.apache.spark.sql.types
+
+import org.apache.spark.SparkFunSuite
+
+class MetadataSuite extends SparkFunSuite {
+  test("String Metadata") {
+    val meta = new MetadataBuilder().putString("key", "value").build()
+    assert(meta === meta)
+    assert(meta.## !== 0)
+    assert(meta.getString("key") === "value")
+    assert(meta.contains("key"))
+    intercept[NoSuchElementException](meta.getString("no_such_key"))
+    intercept[ClassCastException](meta.getBoolean("key"))
+  }
+
+  test("Long Metadata") {
+    val meta = new MetadataBuilder().putLong("key", 12).build()
+    assert(meta === meta)
+    assert(meta.## !== 0)
+    assert(meta.getLong("key") === 12)
+    assert(meta.contains("key"))
+    intercept[NoSuchElementException](meta.getLong("no_such_key"))
+    intercept[ClassCastException](meta.getBoolean("key"))
+  }
+
+  test("Double Metadata") {
+    val meta = new MetadataBuilder().putDouble("key", 12).build()
+    assert(meta === meta)
+    assert(meta.## !== 0)
+    assert(meta.getDouble("key") === 12)
+    assert(meta.contains("key"))
+    intercept[NoSuchElementException](meta.getDouble("no_such_key"))
+    intercept[ClassCastException](meta.getBoolean("key"))
+  }
+
+  test("Boolean Metadata") {
+    val meta = new MetadataBuilder().putBoolean("key", true).build()
+    assert(meta === meta)
+    assert(meta.## !== 0)
+    assert(meta.getBoolean("key") === true)
+    assert(meta.contains("key"))
+    intercept[NoSuchElementException](meta.getBoolean("no_such_key"))
+    intercept[ClassCastException](meta.getString("key"))
+  }
+
+  test("Null Metadata") {
+    val meta = new MetadataBuilder().putNull("key").build()
+    assert(meta === meta)
+    assert(meta.## !== 0)
+    assert(meta.getString("key") === null)
+    assert(meta.getDouble("key") === 0)
+    assert(meta.getLong("key") === 0)
+    assert(meta.getBoolean("key") === false)
+    assert(meta.contains("key"))
+    intercept[NoSuchElementException](meta.getLong("no_such_key"))
+  }
+}