Added contains(key) to Metadata

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

@@ -34,6 +34,9 @@ import org.json4s.jackson.JsonMethods._
  */
 sealed class Metadata private[util] (private[util] val map: Map[String, Any]) extends Serializable {
 
+  /** Tests whether this Metadata contains a binding for a key. */
+  def contains(key: String): Boolean = map.contains(key)
+
   /** Gets a Long. */
   def getLong(key: String): Long = get(key)
 

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

@@ -56,17 +56,30 @@ class MetadataSuite extends FunSuite {
     .build()
 
   test("metadata builder and getters") {
+    assert(age.contains("summary") === false)
+    assert(age.contains("index") === true)
     assert(age.getLong("index") === 1L)
+    assert(age.contains("average") === true)
     assert(age.getDouble("average") === 45.0)
+    assert(age.contains("categorical") === true)
     assert(age.getBoolean("categorical") === false)
+    assert(age.contains("name") === true)
     assert(age.getString("name") === "age")
+    assert(metadata.contains("purpose") === true)
     assert(metadata.getString("purpose") === "ml")
+    assert(metadata.contains("isBase") === true)
     assert(metadata.getBoolean("isBase") === false)
+    assert(metadata.contains("summary") === true)
     assert(metadata.getMetadata("summary") === summary)
+    assert(metadata.contains("long[]") === true)
     assert(metadata.getLongArray("long[]").toSeq === Seq(0L, 1L))
+    assert(metadata.contains("double[]") === true)
     assert(metadata.getDoubleArray("double[]").toSeq === Seq(3.0, 4.0))
+    assert(metadata.contains("boolean[]") === true)
     assert(metadata.getBooleanArray("boolean[]").toSeq === Seq(true, false))
+    assert(gender.contains("categories") === true)
     assert(gender.getStringArray("categories").toSeq === Seq("male", "female"))
+    assert(metadata.contains("features") === true)
     assert(metadata.getMetadataArray("features").toSeq === Seq(age, gender))
   }