diff --git a/python/pyspark/sql.py b/python/pyspark/sql.py
index f0bd3cbd985da..93bfc25bca855 100644
--- a/python/pyspark/sql.py
+++ b/python/pyspark/sql.py
@@ -313,12 +313,15 @@ class StructField(DataType):
 
     """
 
-    def __init__(self, name, dataType, nullable):
+    def __init__(self, name, dataType, nullable, metadata=None):
         """Creates a StructField
         :param name: the name of this field.
         :param dataType: the data type of this field.
         :param nullable: indicates whether values of this field
                          can be null.
+        :param metadata: metadata of this field, which is a map from string
+                         to simple type that can be serialized to JSON
+                         automatically
 
         >>> (StructField("f1", StringType, True)
         ...      == StructField("f1", StringType, True))
@@ -330,6 +333,7 @@ def __init__(self, name, dataType, nullable):
         self.name = name
         self.dataType = dataType
         self.nullable = nullable
+        self.metadata = metadata or {}
 
     def __repr__(self):
         return "StructField(%s,%s,%s)" % (self.name, self.dataType,
@@ -338,13 +342,15 @@ def __repr__(self):
     def jsonValue(self):
         return {"name": self.name,
                 "type": self.dataType.jsonValue(),
-                "nullable": self.nullable}
+                "nullable": self.nullable,
+                "metadata": self.metadata}
 
     @classmethod
     def fromJson(cls, json):
         return StructField(json["name"],
                            _parse_datatype_json_value(json["type"]),
-                           json["nullable"])
+                           json["nullable"],
+                           json["metadata"])
 
 
 class StructType(DataType):
@@ -423,7 +429,8 @@ def _parse_datatype_json_string(json_string):
     ...     StructField("simpleArray", simple_arraytype, True),
     ...     StructField("simpleMap", simple_maptype, True),
     ...     StructField("simpleStruct", simple_structtype, True),
-    ...     StructField("boolean", BooleanType(), False)])
+    ...     StructField("boolean", BooleanType(), False),
+    ...     StructField("withMeta", DoubleType(), False, {"name": "age"})])
     >>> check_datatype(complex_structtype)
     True
     >>> # Complex ArrayType.
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/ScalaReflection.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/ScalaReflection.scala
index d76c743d3f652..75923d9e8d729 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/ScalaReflection.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/ScalaReflection.scala
@@ -46,7 +46,7 @@ object ScalaReflection {
   /** Returns a Sequence of attributes for the given case class type. */
   def attributesFor[T: TypeTag]: Seq[Attribute] = schemaFor[T] match {
     case Schema(s: StructType, _) =>
-      s.fields.map(f => AttributeReference(f.name, f.dataType, f.nullable)())
+      s.fields.map(f => AttributeReference(f.name, f.dataType, f.nullable, f.metadata)())
   }
 
   /** Returns a catalyst DataType and its nullability for the given Scala Type using reflection. */
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/Expression.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/Expression.scala
index 1eb260efa6387..39b120e8de485 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/Expression.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/Expression.scala
@@ -21,6 +21,7 @@ import org.apache.spark.sql.catalyst.errors.TreeNodeException
 import org.apache.spark.sql.catalyst.trees
 import org.apache.spark.sql.catalyst.trees.TreeNode
 import org.apache.spark.sql.catalyst.types.{DataType, FractionalType, IntegralType, NumericType, NativeType}
+import org.apache.spark.sql.catalyst.util.Metadata
 
 abstract class Expression extends TreeNode[Expression] {
   self: Product =>
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/generators.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/generators.scala
index 9c865254e0be9..ab0701fd9a80b 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/generators.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/generators.scala
@@ -43,7 +43,7 @@ abstract class Generator extends Expression {
   override type EvaluatedType = TraversableOnce[Row]
 
   override lazy val dataType =
-    ArrayType(StructType(output.map(a => StructField(a.name, a.dataType, a.nullable))))
+    ArrayType(StructType(output.map(a => StructField(a.name, a.dataType, a.nullable, a.metadata))))
 
   override def nullable = false
 
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/namedExpressions.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/namedExpressions.scala
index fe13a661f6f7a..3310566087b3d 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/namedExpressions.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/namedExpressions.scala
@@ -21,6 +21,7 @@ import org.apache.spark.sql.catalyst.trees
 import org.apache.spark.sql.catalyst.analysis.UnresolvedAttribute
 import org.apache.spark.sql.catalyst.errors.TreeNodeException
 import org.apache.spark.sql.catalyst.types._
+import org.apache.spark.sql.catalyst.util.Metadata
 
 object NamedExpression {
   private val curId = new java.util.concurrent.atomic.AtomicLong()
@@ -43,6 +44,9 @@ abstract class NamedExpression extends Expression {
 
   def toAttribute: Attribute
 
+  /** Returns the metadata when an expression is a reference to another expression with metadata. */
+  def metadata: Metadata = Metadata.empty
+
   protected def typeSuffix =
     if (resolved) {
       dataType match {
@@ -88,10 +92,16 @@ case class Alias(child: Expression, name: String)
 
   override def dataType = child.dataType
   override def nullable = child.nullable
+  override def metadata: Metadata = {
+    child match {
+      case named: NamedExpression => named.metadata
+      case _ => Metadata.empty
+    }
+  }
 
   override def toAttribute = {
     if (resolved) {
-      AttributeReference(name, child.dataType, child.nullable)(exprId, qualifiers)
+      AttributeReference(name, child.dataType, child.nullable, metadata)(exprId, qualifiers)
     } else {
       UnresolvedAttribute(name)
     }
@@ -108,15 +118,20 @@ case class Alias(child: Expression, name: String)
  * @param name The name of this attribute, should only be used during analysis or for debugging.
  * @param dataType The [[DataType]] of this attribute.
  * @param nullable True if null is a valid value for this attribute.
+ * @param metadata The metadata of this attribute.
  * @param exprId A globally unique id used to check if different AttributeReferences refer to the
  *               same attribute.
  * @param qualifiers a list of strings that can be used to referred to this attribute in a fully
  *                   qualified way. Consider the examples tableName.name, subQueryAlias.name.
  *                   tableName and subQueryAlias are possible qualifiers.
  */
-case class AttributeReference(name: String, dataType: DataType, nullable: Boolean = true)
-    (val exprId: ExprId = NamedExpression.newExprId, val qualifiers: Seq[String] = Nil)
-  extends Attribute with trees.LeafNode[Expression] {
+case class AttributeReference(
+    name: String,
+    dataType: DataType,
+    nullable: Boolean = true,
+    override val metadata: Metadata = Metadata.empty)(
+    val exprId: ExprId = NamedExpression.newExprId,
+    val qualifiers: Seq[String] = Nil) extends Attribute with trees.LeafNode[Expression] {
 
   override def equals(other: Any) = other match {
     case ar: AttributeReference => exprId == ar.exprId && dataType == ar.dataType
@@ -128,10 +143,12 @@ case class AttributeReference(name: String, dataType: DataType, nullable: Boolea
     var h = 17
     h = h * 37 + exprId.hashCode()
     h = h * 37 + dataType.hashCode()
+    h = h * 37 + metadata.hashCode()
     h
   }
 
-  override def newInstance() = AttributeReference(name, dataType, nullable)(qualifiers = qualifiers)
+  override def newInstance() =
+    AttributeReference(name, dataType, nullable, metadata)(qualifiers = qualifiers)
 
   /**
    * Returns a copy of this [[AttributeReference]] with changed nullability.
@@ -140,7 +157,7 @@ case class AttributeReference(name: String, dataType: DataType, nullable: Boolea
     if (nullable == newNullability) {
       this
     } else {
-      AttributeReference(name, dataType, newNullability)(exprId, qualifiers)
+      AttributeReference(name, dataType, newNullability, metadata)(exprId, qualifiers)
     }
   }
 
@@ -159,7 +176,7 @@ case class AttributeReference(name: String, dataType: DataType, nullable: Boolea
     if (newQualifiers.toSet == qualifiers.toSet) {
       this
     } else {
-      AttributeReference(name, dataType, nullable)(exprId, newQualifiers)
+      AttributeReference(name, dataType, nullable, metadata)(exprId, newQualifiers)
     }
   }
 
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/types/dataTypes.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/types/dataTypes.scala
index 4e6e1166bfffb..6069f9b0a68dc 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/types/dataTypes.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/types/dataTypes.scala
@@ -24,16 +24,16 @@ import scala.reflect.ClassTag
 import scala.reflect.runtime.universe.{TypeTag, runtimeMirror, typeTag}
 import scala.util.parsing.combinator.RegexParsers
 
-import org.json4s.JsonAST.JValue
 import org.json4s._
+import org.json4s.JsonAST.JValue
 import org.json4s.JsonDSL._
 import org.json4s.jackson.JsonMethods._
 
 import org.apache.spark.sql.catalyst.ScalaReflectionLock
 import org.apache.spark.sql.catalyst.expressions.{Attribute, AttributeReference, Expression}
+import org.apache.spark.sql.catalyst.util.Metadata
 import org.apache.spark.util.Utils
 
-
 object DataType {
   def fromJson(json: String): DataType = parseDataType(parse(json))
 
@@ -70,10 +70,11 @@ object DataType {
 
   private def parseStructField(json: JValue): StructField = json match {
     case JSortedObject(
+        ("metadata", metadata: JObject),
         ("name", JString(name)),
         ("nullable", JBool(nullable)),
         ("type", dataType: JValue)) =>
-      StructField(name, parseDataType(dataType), nullable)
+      StructField(name, parseDataType(dataType), nullable, Metadata.fromJObject(metadata))
   }
 
   @deprecated("Use DataType.fromJson instead", "1.2.0")
@@ -388,24 +389,34 @@ case class ArrayType(elementType: DataType, containsNull: Boolean) extends DataT
  * @param name The name of this field.
  * @param dataType The data type of this field.
  * @param nullable Indicates if values of this field can be `null` values.
+ * @param metadata The metadata of this field. The metadata should be preserved during
+ *                 transformation if the content of the column is not modified, e.g, in selection.
  */
-case class StructField(name: String, dataType: DataType, nullable: Boolean) {
+case class StructField(
+    name: String,
+    dataType: DataType,
+    nullable: Boolean,
+    metadata: Metadata = Metadata.empty) {
 
   private[sql] def buildFormattedString(prefix: String, builder: StringBuilder): Unit = {
     builder.append(s"$prefix-- $name: ${dataType.typeName} (nullable = $nullable)\n")
     DataType.buildFormattedString(dataType, s"$prefix    |", builder)
   }
 
+  // override the default toString to be compatible with legacy parquet files.
+  override def toString: String = s"StructField($name,$dataType,$nullable)"
+
   private[sql] def jsonValue: JValue = {
     ("name" -> name) ~
       ("type" -> dataType.jsonValue) ~
-      ("nullable" -> nullable)
+      ("nullable" -> nullable) ~
+      ("metadata" -> metadata.jsonValue)
   }
 }
 
 object StructType {
   protected[sql] def fromAttributes(attributes: Seq[Attribute]): StructType =
-    StructType(attributes.map(a => StructField(a.name, a.dataType, a.nullable)))
+    StructType(attributes.map(a => StructField(a.name, a.dataType, a.nullable, a.metadata)))
 }
 
 case class StructType(fields: Seq[StructField]) extends DataType {
@@ -439,7 +450,7 @@ case class StructType(fields: Seq[StructField]) extends DataType {
   }
 
   protected[sql] def toAttributes =
-    fields.map(f => AttributeReference(f.name, f.dataType, f.nullable)())
+    fields.map(f => AttributeReference(f.name, f.dataType, f.nullable, f.metadata)())
 
   def treeString: String = {
     val builder = new StringBuilder
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/util/Metadata.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/util/Metadata.scala
new file mode 100644
index 0000000000000..2f2082fa3c863
--- /dev/null
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/util/Metadata.scala
@@ -0,0 +1,255 @@
+/*
+ * 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.catalyst.util
+
+import scala.collection.mutable
+
+import org.json4s._
+import org.json4s.jackson.JsonMethods._
+
+/**
+ * Metadata is a wrapper over Map[String, Any] that limits the value type to simple ones: Boolean,
+ * Long, Double, String, Metadata, Array[Boolean], Array[Long], Array[Double], Array[String], and
+ * Array[Metadata]. JSON is used for serialization.
+ *
+ * The default constructor is private. User should use either [[MetadataBuilder]] or
+ * [[Metadata$#fromJson]] to create Metadata instances.
+ *
+ * @param map an immutable map that stores the data
+ */
+sealed class Metadata private[util] (private[util] val map: Map[String, Any]) extends Serializable {
+
+  /** Gets a Long. */
+  def getLong(key: String): Long = get(key)
+
+  /** Gets a Double. */
+  def getDouble(key: String): Double = get(key)
+
+  /** Gets a Boolean. */
+  def getBoolean(key: String): Boolean = get(key)
+
+  /** Gets a String. */
+  def getString(key: String): String = get(key)
+
+  /** Gets a Metadata. */
+  def getMetadata(key: String): Metadata = get(key)
+
+  /** Gets a Long array. */
+  def getLongArray(key: String): Array[Long] = get(key)
+
+  /** Gets a Double array. */
+  def getDoubleArray(key: String): Array[Double] = get(key)
+
+  /** Gets a Boolean array. */
+  def getBooleanArray(key: String): Array[Boolean] = get(key)
+
+  /** Gets a String array. */
+  def getStringArray(key: String): Array[String] = get(key)
+
+  /** Gets a Metadata array. */
+  def getMetadataArray(key: String): Array[Metadata] = get(key)
+
+  /** Converts to its JSON representation. */
+  def json: String = compact(render(jsonValue))
+
+  override def toString: String = json
+
+  override def equals(obj: Any): Boolean = {
+    obj match {
+      case that: Metadata =>
+        if (map.keySet == that.map.keySet) {
+          map.keys.forall { k =>
+            (map(k), that.map(k)) match {
+              case (v0: Array[_], v1: Array[_]) =>
+                v0.view == v1.view
+              case (v0, v1) =>
+                v0 == v1
+            }
+          }
+        } else {
+          false
+        }
+      case other =>
+        false
+    }
+  }
+
+  override def hashCode: Int = Metadata.hash(this)
+
+  private def get[T](key: String): T = {
+    map(key).asInstanceOf[T]
+  }
+
+  private[sql] def jsonValue: JValue = Metadata.toJsonValue(this)
+}
+
+object Metadata {
+
+  /** Returns an empty Metadata. */
+  def empty: Metadata = new Metadata(Map.empty)
+
+  /** Creates a Metadata instance from JSON. */
+  def fromJson(json: String): Metadata = {
+    fromJObject(parse(json).asInstanceOf[JObject])
+  }
+
+  /** Creates a Metadata instance from JSON AST. */
+  private[sql] def fromJObject(jObj: JObject): Metadata = {
+    val builder = new MetadataBuilder
+    jObj.obj.foreach {
+      case (key, JInt(value)) =>
+        builder.putLong(key, value.toLong)
+      case (key, JDouble(value)) =>
+        builder.putDouble(key, value)
+      case (key, JBool(value)) =>
+        builder.putBoolean(key, value)
+      case (key, JString(value)) =>
+        builder.putString(key, value)
+      case (key, o: JObject) =>
+        builder.putMetadata(key, fromJObject(o))
+      case (key, JArray(value)) =>
+        if (value.isEmpty) {
+          // If it is an empty array, we cannot infer its element type. We put an empty Array[Long].
+          builder.putLongArray(key, Array.empty)
+        } else {
+          value.head match {
+            case _: JInt =>
+              builder.putLongArray(key, value.asInstanceOf[List[JInt]].map(_.num.toLong).toArray)
+            case _: JDouble =>
+              builder.putDoubleArray(key, value.asInstanceOf[List[JDouble]].map(_.num).toArray)
+            case _: JBool =>
+              builder.putBooleanArray(key, value.asInstanceOf[List[JBool]].map(_.value).toArray)
+            case _: JString =>
+              builder.putStringArray(key, value.asInstanceOf[List[JString]].map(_.s).toArray)
+            case _: JObject =>
+              builder.putMetadataArray(
+                key, value.asInstanceOf[List[JObject]].map(fromJObject).toArray)
+            case other =>
+              throw new RuntimeException(s"Do not support array of type ${other.getClass}.")
+          }
+        }
+      case other =>
+        throw new RuntimeException(s"Do not support type ${other.getClass}.")
+    }
+    builder.build()
+  }
+
+  /** Converts to JSON AST. */
+  private def toJsonValue(obj: Any): JValue = {
+    obj match {
+      case map: Map[_, _] =>
+        val fields = map.toList.map { case (k: String, v) => (k, toJsonValue(v)) }
+        JObject(fields)
+      case arr: Array[_] =>
+        val values = arr.toList.map(toJsonValue)
+        JArray(values)
+      case x: Long =>
+        JInt(x)
+      case x: Double =>
+        JDouble(x)
+      case x: Boolean =>
+        JBool(x)
+      case x: String =>
+        JString(x)
+      case x: Metadata =>
+        toJsonValue(x.map)
+      case other =>
+        throw new RuntimeException(s"Do not support type ${other.getClass}.")
+    }
+  }
+
+  /** Computes the hash code for the types we support. */
+  private def hash(obj: Any): Int = {
+    obj match {
+      case map: Map[_, _] =>
+        map.mapValues(hash).##
+      case arr: Array[_] =>
+        // Seq.empty[T] has the same hashCode regardless of T.
+        arr.toSeq.map(hash).##
+      case x: Long =>
+        x.##
+      case x: Double =>
+        x.##
+      case x: Boolean =>
+        x.##
+      case x: String =>
+        x.##
+      case x: Metadata =>
+        hash(x.map)
+      case other =>
+        throw new RuntimeException(s"Do not support type ${other.getClass}.")
+    }
+  }
+}
+
+/**
+ * Builder for [[Metadata]]. If there is a key collision, the latter will overwrite the former.
+ */
+class MetadataBuilder {
+
+  private val map: mutable.Map[String, Any] = mutable.Map.empty
+
+  /** Returns the immutable version of this map.  Used for java interop. */
+  protected def getMap = map.toMap
+
+  /** Include the content of an existing [[Metadata]] instance. */
+  def withMetadata(metadata: Metadata): this.type = {
+    map ++= metadata.map
+    this
+  }
+
+  /** Puts a Long. */
+  def putLong(key: String, value: Long): this.type = put(key, value)
+
+  /** Puts a Double. */
+  def putDouble(key: String, value: Double): this.type = put(key, value)
+
+  /** Puts a Boolean. */
+  def putBoolean(key: String, value: Boolean): this.type = put(key, value)
+
+  /** Puts a String. */
+  def putString(key: String, value: String): this.type = put(key, value)
+
+  /** Puts a [[Metadata]]. */
+  def putMetadata(key: String, value: Metadata): this.type = put(key, value)
+
+  /** Puts a Long array. */
+  def putLongArray(key: String, value: Array[Long]): this.type = put(key, value)
+
+  /** Puts a Double array. */
+  def putDoubleArray(key: String, value: Array[Double]): this.type = put(key, value)
+
+  /** Puts a Boolean array. */
+  def putBooleanArray(key: String, value: Array[Boolean]): this.type = put(key, value)
+
+  /** Puts a String array. */
+  def putStringArray(key: String, value: Array[String]): this.type = put(key, value)
+
+  /** Puts a [[Metadata]] array. */
+  def putMetadataArray(key: String, value: Array[Metadata]): this.type = put(key, value)
+
+  /** Builds the [[Metadata]] instance. */
+  def build(): Metadata = {
+    new Metadata(map.toMap)
+  }
+
+  private def put(key: String, value: Any): this.type = {
+    map.put(key, value)
+    this
+  }
+}
diff --git a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/util/MetadataSuite.scala b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/util/MetadataSuite.scala
new file mode 100644
index 0000000000000..0063d31666c85
--- /dev/null
+++ b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/util/MetadataSuite.scala
@@ -0,0 +1,82 @@
+/*
+ * 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.catalyst.util
+
+import org.json4s.jackson.JsonMethods.parse
+import org.scalatest.FunSuite
+
+class MetadataSuite extends FunSuite {
+
+  val baseMetadata = new MetadataBuilder()
+    .putString("purpose", "ml")
+    .putBoolean("isBase", true)
+    .build()
+
+  val summary = new MetadataBuilder()
+    .putLong("numFeatures", 10L)
+    .build()
+
+  val age = new MetadataBuilder()
+    .putString("name", "age")
+    .putLong("index", 1L)
+    .putBoolean("categorical", false)
+    .putDouble("average", 45.0)
+    .build()
+
+  val gender = new MetadataBuilder()
+    .putString("name", "gender")
+    .putLong("index", 5)
+    .putBoolean("categorical", true)
+    .putStringArray("categories", Array("male", "female"))
+    .build()
+
+  val metadata = new MetadataBuilder()
+    .withMetadata(baseMetadata)
+    .putBoolean("isBase", false) // overwrite an existing key
+    .putMetadata("summary", summary)
+    .putLongArray("long[]", Array(0L, 1L))
+    .putDoubleArray("double[]", Array(3.0, 4.0))
+    .putBooleanArray("boolean[]", Array(true, false))
+    .putMetadataArray("features", Array(age, gender))
+    .build()
+
+  test("metadata builder and getters") {
+    assert(age.getLong("index") === 1L)
+    assert(age.getDouble("average") === 45.0)
+    assert(age.getBoolean("categorical") === false)
+    assert(age.getString("name") === "age")
+    assert(metadata.getString("purpose") === "ml")
+    assert(metadata.getBoolean("isBase") === false)
+    assert(metadata.getMetadata("summary") === summary)
+    assert(metadata.getLongArray("long[]").toSeq === Seq(0L, 1L))
+    assert(metadata.getDoubleArray("double[]").toSeq === Seq(3.0, 4.0))
+    assert(metadata.getBooleanArray("boolean[]").toSeq === Seq(true, false))
+    assert(gender.getStringArray("categories").toSeq === Seq("male", "female"))
+    assert(metadata.getMetadataArray("features").toSeq === Seq(age, gender))
+  }
+
+  test("metadata json conversion") {
+    val json = metadata.json
+    withClue("toJson must produce a valid JSON string") {
+      parse(json)
+    }
+    val parsed = Metadata.fromJson(json)
+    assert(parsed === metadata)
+    assert(parsed.## === metadata.##)
+  }
+}
diff --git a/sql/core/src/main/java/org/apache/spark/sql/api/java/DataType.java b/sql/core/src/main/java/org/apache/spark/sql/api/java/DataType.java
index 37e88d72b9172..0c85cdc0aa640 100644
--- a/sql/core/src/main/java/org/apache/spark/sql/api/java/DataType.java
+++ b/sql/core/src/main/java/org/apache/spark/sql/api/java/DataType.java
@@ -17,9 +17,7 @@
 
 package org.apache.spark.sql.api.java;
 
-import java.util.HashSet;
-import java.util.List;
-import java.util.Set;
+import java.util.*;
 
 /**
  * The base type of all Spark SQL data types.
@@ -151,15 +149,31 @@ public static MapType createMapType(
    * Creates a StructField by specifying the name ({@code name}), data type ({@code dataType}) and
    * whether values of this field can be null values ({@code nullable}).
    */
-  public static StructField createStructField(String name, DataType dataType, boolean nullable) {
+  public static StructField createStructField(
+      String name,
+      DataType dataType,
+      boolean nullable,
+      Metadata metadata) {
     if (name == null) {
       throw new IllegalArgumentException("name should not be null.");
     }
     if (dataType == null) {
       throw new IllegalArgumentException("dataType should not be null.");
     }
+    if (metadata == null) {
+      throw new IllegalArgumentException("metadata should not be null.");
+    }
+
+    return new StructField(name, dataType, nullable, metadata);
+  }
 
-    return new StructField(name, dataType, nullable);
+  /**
+   * Creates a StructField with empty metadata.
+   *
+   * @see #createStructField(String, DataType, boolean, Metadata)
+   */
+  public static StructField createStructField(String name, DataType dataType, boolean nullable) {
+    return createStructField(name, dataType, nullable, (new MetadataBuilder()).build());
   }
 
   /**
@@ -191,5 +205,4 @@ public static StructType createStructType(StructField[] fields) {
 
     return new StructType(fields);
   }
-
 }
diff --git a/sql/core/src/main/java/org/apache/spark/sql/api/java/Metadata.java b/sql/core/src/main/java/org/apache/spark/sql/api/java/Metadata.java
new file mode 100644
index 0000000000000..0f819fb01a76a
--- /dev/null
+++ b/sql/core/src/main/java/org/apache/spark/sql/api/java/Metadata.java
@@ -0,0 +1,31 @@
+/*
+ * 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.api.java;
+
+/**
+ * Metadata is a wrapper over Map[String, Any] that limits the value type to simple ones: Boolean,
+ * Long, Double, String, Metadata, Array[Boolean], Array[Long], Array[Double], Array[String], and
+ * Array[Metadata]. JSON is used for serialization.
+ *
+ * The default constructor is private. User should use [[MetadataBuilder]].
+ */
+class Metadata extends org.apache.spark.sql.catalyst.util.Metadata {
+  Metadata(scala.collection.immutable.Map<String, Object> map) {
+    super(map);
+  }
+}
diff --git a/sql/core/src/main/java/org/apache/spark/sql/api/java/MetadataBuilder.java b/sql/core/src/main/java/org/apache/spark/sql/api/java/MetadataBuilder.java
new file mode 100644
index 0000000000000..6e6b12f0722c5
--- /dev/null
+++ b/sql/core/src/main/java/org/apache/spark/sql/api/java/MetadataBuilder.java
@@ -0,0 +1,28 @@
+/*
+ * 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.api.java;
+
+/**
+ * Builder for [[Metadata]]. If there is a key collision, the latter will overwrite the former.
+ */
+public class MetadataBuilder extends org.apache.spark.sql.catalyst.util.MetadataBuilder {
+  @Override
+  public Metadata build() {
+    return new Metadata(getMap());
+  }
+}
diff --git a/sql/core/src/main/java/org/apache/spark/sql/api/java/StructField.java b/sql/core/src/main/java/org/apache/spark/sql/api/java/StructField.java
index b48e2a2c5f953..7c60d492bcdf0 100644
--- a/sql/core/src/main/java/org/apache/spark/sql/api/java/StructField.java
+++ b/sql/core/src/main/java/org/apache/spark/sql/api/java/StructField.java
@@ -17,6 +17,8 @@
 
 package org.apache.spark.sql.api.java;
 
+import java.util.Map;
+
 /**
  * A StructField object represents a field in a StructType object.
  * A StructField object comprises three fields, {@code String name}, {@code DataType dataType},
@@ -24,20 +26,27 @@
  * The field of {@code dataType} specifies the data type of a StructField.
  * The field of {@code nullable} specifies if values of a StructField can contain {@code null}
  * values.
+ * The field of {@code metadata} provides extra information of the StructField.
  *
  * To create a {@link StructField},
- * {@link DataType#createStructField(String, DataType, boolean)}
+ * {@link DataType#createStructField(String, DataType, boolean, Metadata)}
  * should be used.
  */
 public class StructField {
   private String name;
   private DataType dataType;
   private boolean nullable;
+  private Metadata metadata;
 
-  protected StructField(String name, DataType dataType, boolean nullable) {
+  protected StructField(
+      String name,
+      DataType dataType,
+      boolean nullable,
+      Metadata metadata) {
     this.name = name;
     this.dataType = dataType;
     this.nullable = nullable;
+    this.metadata = metadata;
   }
 
   public String getName() {
@@ -52,6 +61,10 @@ public boolean isNullable() {
     return nullable;
   }
 
+  public Metadata getMetadata() {
+    return metadata;
+  }
+
   @Override
   public boolean equals(Object o) {
     if (this == o) return true;
@@ -62,6 +75,7 @@ public boolean equals(Object o) {
     if (nullable != that.nullable) return false;
     if (!dataType.equals(that.dataType)) return false;
     if (!name.equals(that.name)) return false;
+    if (!metadata.equals(that.metadata)) return false;
 
     return true;
   }
@@ -71,6 +85,7 @@ public int hashCode() {
     int result = name.hashCode();
     result = 31 * result + dataType.hashCode();
     result = 31 * result + (nullable ? 1 : 0);
+    result = 31 * result + metadata.hashCode();
     return result;
   }
 }
diff --git a/sql/core/src/main/scala/org/apache/spark/sql/SQLContext.scala b/sql/core/src/main/scala/org/apache/spark/sql/SQLContext.scala
index a41a500c9a5d0..4953f8399a96b 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/SQLContext.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/SQLContext.scala
@@ -32,7 +32,6 @@ import org.apache.spark.sql.catalyst.expressions._
 import org.apache.spark.sql.catalyst.optimizer.{Optimizer, DefaultOptimizer}
 import org.apache.spark.sql.catalyst.plans.logical.LogicalPlan
 import org.apache.spark.sql.catalyst.rules.RuleExecutor
-import org.apache.spark.sql.catalyst.types.DataType
 import org.apache.spark.sql.execution.{SparkStrategies, _}
 import org.apache.spark.sql.json._
 import org.apache.spark.sql.parquet.ParquetRelation
diff --git a/sql/core/src/main/scala/org/apache/spark/sql/json/JsonRDD.scala b/sql/core/src/main/scala/org/apache/spark/sql/json/JsonRDD.scala
index 047dc85df6c1d..eabe312f92371 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/json/JsonRDD.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/json/JsonRDD.scala
@@ -117,10 +117,7 @@ private[sql] object JsonRDD extends Logging {
         }
       }.flatMap(field => field).toSeq
 
-      StructType(
-        (topLevelFields ++ structFields).sortBy {
-        case StructField(name, _, _) => name
-      })
+      StructType((topLevelFields ++ structFields).sortBy(_.name))
     }
 
     makeStruct(resolved.keySet.toSeq, Nil)
@@ -128,7 +125,7 @@ private[sql] object JsonRDD extends Logging {
 
   private[sql] def nullTypeToStringType(struct: StructType): StructType = {
     val fields = struct.fields.map {
-      case StructField(fieldName, dataType, nullable) => {
+      case StructField(fieldName, dataType, nullable, _) => {
         val newType = dataType match {
           case NullType => StringType
           case ArrayType(NullType, containsNull) => ArrayType(StringType, containsNull)
@@ -163,9 +160,7 @@ private[sql] object JsonRDD extends Logging {
                 StructField(name, dataType, true)
               }
             }
-            StructType(newFields.toSeq.sortBy {
-              case StructField(name, _, _) => name
-            })
+            StructType(newFields.toSeq.sortBy(_.name))
           }
           case (ArrayType(elementType1, containsNull1), ArrayType(elementType2, containsNull2)) =>
             ArrayType(compatibleType(elementType1, elementType2), containsNull1 || containsNull2)
@@ -413,7 +408,7 @@ private[sql] object JsonRDD extends Logging {
     // TODO: Reuse the row instead of creating a new one for every record.
     val row = new GenericMutableRow(schema.fields.length)
     schema.fields.zipWithIndex.foreach {
-      case (StructField(name, dataType, _), i) =>
+      case (StructField(name, dataType, _, _), i) =>
         row.update(i, json.get(name).flatMap(v => Option(v)).map(
           enforceCorrectType(_, dataType)).orNull)
     }
diff --git a/sql/core/src/main/scala/org/apache/spark/sql/package.scala b/sql/core/src/main/scala/org/apache/spark/sql/package.scala
index e98d151286818..f0e57e2a7447b 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/package.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/package.scala
@@ -125,6 +125,9 @@ package object sql {
   @DeveloperApi
   type DataType = catalyst.types.DataType
 
+  @DeveloperApi
+  val DataType = catalyst.types.DataType
+
   /**
    * :: DeveloperApi ::
    *
@@ -414,4 +417,24 @@ package object sql {
    */
   @DeveloperApi
   val StructField = catalyst.types.StructField
+
+  /**
+   * :: DeveloperApi ::
+   *
+   * Metadata is a wrapper over Map[String, Any] that limits the value type to simple ones: Boolean,
+   * Long, Double, String, Metadata, Array[Boolean], Array[Long], Array[Double], Array[String], and
+   * Array[Metadata]. JSON is used for serialization.
+   *
+   * The default constructor is private. User should use either [[MetadataBuilder]] or
+   * [[Metadata$#fromJson]] to create Metadata instances.
+   *
+   * @param map an immutable map that stores the data
+   */
+  @DeveloperApi
+  type Metadata = catalyst.util.Metadata
+
+  /**
+   * Builder for [[Metadata]]. If there is a key collision, the latter will overwrite the former.
+   */
+  type MetadataBuilder = catalyst.util.MetadataBuilder
 }
diff --git a/sql/core/src/main/scala/org/apache/spark/sql/types/util/DataTypeConversions.scala b/sql/core/src/main/scala/org/apache/spark/sql/types/util/DataTypeConversions.scala
index 609f7db562a31..142598c904b37 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/types/util/DataTypeConversions.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/types/util/DataTypeConversions.scala
@@ -18,7 +18,7 @@
 package org.apache.spark.sql.types.util
 
 import org.apache.spark.sql._
-import org.apache.spark.sql.api.java.{DataType => JDataType, StructField => JStructField}
+import org.apache.spark.sql.api.java.{DataType => JDataType, StructField => JStructField, MetadataBuilder => JMetaDataBuilder}
 
 import scala.collection.JavaConverters._
 
@@ -31,7 +31,8 @@ protected[sql] object DataTypeConversions {
     JDataType.createStructField(
       scalaStructField.name,
       asJavaDataType(scalaStructField.dataType),
-      scalaStructField.nullable)
+      scalaStructField.nullable,
+      (new JMetaDataBuilder).withMetadata(scalaStructField.metadata).build())
   }
 
   /**
@@ -68,7 +69,8 @@ protected[sql] object DataTypeConversions {
     StructField(
       javaStructField.getName,
       asScalaDataType(javaStructField.getDataType),
-      javaStructField.isNullable)
+      javaStructField.isNullable,
+      javaStructField.getMetadata)
   }
 
   /**
diff --git a/sql/core/src/test/scala/org/apache/spark/sql/DataTypeSuite.scala b/sql/core/src/test/scala/org/apache/spark/sql/DataTypeSuite.scala
index 100ecb45e9e88..6c9db639c0f6c 100644
--- a/sql/core/src/test/scala/org/apache/spark/sql/DataTypeSuite.scala
+++ b/sql/core/src/test/scala/org/apache/spark/sql/DataTypeSuite.scala
@@ -19,8 +19,6 @@ package org.apache.spark.sql
 
 import org.scalatest.FunSuite
 
-import org.apache.spark.sql.catalyst.types.DataType
-
 class DataTypeSuite extends FunSuite {
 
   test("construct an ArrayType") {
@@ -79,8 +77,12 @@ class DataTypeSuite extends FunSuite {
   checkDataTypeJsonRepr(ArrayType(StringType, false))
   checkDataTypeJsonRepr(MapType(IntegerType, StringType, true))
   checkDataTypeJsonRepr(MapType(IntegerType, ArrayType(DoubleType), false))
+  val metadata = new MetadataBuilder()
+    .putString("name", "age")
+    .build()
   checkDataTypeJsonRepr(
     StructType(Seq(
       StructField("a", IntegerType, nullable = true),
-      StructField("b", ArrayType(DoubleType), nullable = false))))
+      StructField("b", ArrayType(DoubleType), nullable = false),
+      StructField("c", DoubleType, nullable = false, metadata))))
 }
diff --git a/sql/core/src/test/scala/org/apache/spark/sql/SQLQuerySuite.scala b/sql/core/src/test/scala/org/apache/spark/sql/SQLQuerySuite.scala
index 4acd92d33d180..6befe1b755cc6 100644
--- a/sql/core/src/test/scala/org/apache/spark/sql/SQLQuerySuite.scala
+++ b/sql/core/src/test/scala/org/apache/spark/sql/SQLQuerySuite.scala
@@ -17,17 +17,16 @@
 
 package org.apache.spark.sql
 
+import java.util.TimeZone
+
+import org.scalatest.BeforeAndAfterAll
+
+import org.apache.spark.sql.TestData._
 import org.apache.spark.sql.catalyst.errors.TreeNodeException
 import org.apache.spark.sql.catalyst.expressions._
 import org.apache.spark.sql.catalyst.plans.logical.LogicalPlan
-import org.apache.spark.sql.execution.joins.BroadcastHashJoin
-import org.apache.spark.sql.test._
-import org.scalatest.BeforeAndAfterAll
-import java.util.TimeZone
 
-/* Implicits */
-import TestSQLContext._
-import TestData._
+import org.apache.spark.sql.test.TestSQLContext._
 
 class SQLQuerySuite extends QueryTest with BeforeAndAfterAll {
   // Make sure the tables are loaded.
@@ -697,6 +696,30 @@ class SQLQuerySuite extends QueryTest with BeforeAndAfterAll {
       ("true", "false") :: Nil)
   }
 
+  test("metadata is propagated correctly") {
+    val person = sql("SELECT * FROM person")
+    val schema = person.schema
+    val docKey = "doc"
+    val docValue = "first name"
+    val metadata = new MetadataBuilder()
+      .putString(docKey, docValue)
+      .build()
+    val schemaWithMeta = new StructType(Seq(
+      schema("id"), schema("name").copy(metadata = metadata), schema("age")))
+    val personWithMeta = applySchema(person, schemaWithMeta)
+    def validateMetadata(rdd: SchemaRDD): Unit = {
+      assert(rdd.schema("name").metadata.getString(docKey) == docValue)
+    }
+    personWithMeta.registerTempTable("personWithMeta")
+    validateMetadata(personWithMeta.select('name))
+    validateMetadata(personWithMeta.select("name".attr))
+    validateMetadata(personWithMeta.select('id, 'name))
+    validateMetadata(sql("SELECT * FROM personWithMeta"))
+    validateMetadata(sql("SELECT id, name FROM personWithMeta"))
+    validateMetadata(sql("SELECT * FROM personWithMeta JOIN salary ON id = personId"))
+    validateMetadata(sql("SELECT name, salary FROM personWithMeta JOIN salary ON id = personId"))
+  }
+  
   test("SPARK-3371 Renaming a function expression with group by gives error") {
     registerFunction("len", (s: String) => s.length)
     checkAnswer(
diff --git a/sql/core/src/test/scala/org/apache/spark/sql/TestData.scala b/sql/core/src/test/scala/org/apache/spark/sql/TestData.scala
index c4dd3e860f5fd..836dd17fcc3a2 100644
--- a/sql/core/src/test/scala/org/apache/spark/sql/TestData.scala
+++ b/sql/core/src/test/scala/org/apache/spark/sql/TestData.scala
@@ -166,4 +166,15 @@ object TestData {
   // An RDD with 4 elements and 8 partitions
   val withEmptyParts = TestSQLContext.sparkContext.parallelize((1 to 4).map(IntField), 8)
   withEmptyParts.registerTempTable("withEmptyParts")
+
+  case class Person(id: Int, name: String, age: Int)
+  case class Salary(personId: Int, salary: Double)
+  val person = TestSQLContext.sparkContext.parallelize(
+    Person(0, "mike", 30) ::
+    Person(1, "jim", 20) :: Nil)
+  person.registerTempTable("person")
+  val salary = TestSQLContext.sparkContext.parallelize(
+    Salary(0, 2000.0) ::
+    Salary(1, 1000.0) :: Nil)
+  salary.registerTempTable("salary")
 }
diff --git a/sql/core/src/test/scala/org/apache/spark/sql/api/java/ScalaSideDataTypeConversionSuite.scala b/sql/core/src/test/scala/org/apache/spark/sql/api/java/ScalaSideDataTypeConversionSuite.scala
index 8415af41be3af..e0e0ff9cb3d3d 100644
--- a/sql/core/src/test/scala/org/apache/spark/sql/api/java/ScalaSideDataTypeConversionSuite.scala
+++ b/sql/core/src/test/scala/org/apache/spark/sql/api/java/ScalaSideDataTypeConversionSuite.scala
@@ -17,12 +17,10 @@
 
 package org.apache.spark.sql.api.java
 
-import org.apache.spark.sql.types.util.DataTypeConversions
 import org.scalatest.FunSuite
 
-import org.apache.spark.sql.{DataType => SDataType, StructField => SStructField}
-import org.apache.spark.sql.{StructType => SStructType}
-import DataTypeConversions._
+import org.apache.spark.sql.{DataType => SDataType, StructField => SStructField, StructType => SStructType}
+import org.apache.spark.sql.types.util.DataTypeConversions._
 
 class ScalaSideDataTypeConversionSuite extends FunSuite {
 
@@ -67,11 +65,15 @@ class ScalaSideDataTypeConversionSuite extends FunSuite {
     checkDataType(simpleScalaStructType)
 
     // Complex StructType.
+    val metadata = new MetadataBuilder()
+      .putString("name", "age")
+      .build()
     val complexScalaStructType = SStructType(
       SStructField("simpleArray", simpleScalaArrayType, true) ::
       SStructField("simpleMap", simpleScalaMapType, true) ::
       SStructField("simpleStruct", simpleScalaStructType, true) ::
-      SStructField("boolean", org.apache.spark.sql.BooleanType, false) :: Nil)
+      SStructField("boolean", org.apache.spark.sql.BooleanType, false) ::
+      SStructField("withMeta", org.apache.spark.sql.DoubleType, false, metadata) :: Nil)
     checkDataType(complexScalaStructType)
 
     // Complex ArrayType.