Github user dilipbiswal commented on a diff in the pull request:
https://github.com/apache/spark/pull/10060#discussion_r46244815
--- Diff: sql/catalyst/src/main/scala/org/apache/spark/sql/Encoder.scala ---
@@ -26,13 +29,51 @@ import
org.apache.spark.sql.catalyst.expressions.{DecodeUsingSerializer, BoundRe
import org.apache.spark.sql.types._
/**
+ * :: Experimental ::
* Used to convert a JVM object of type `T` to and from the internal Spark
SQL representation.
*
- * Encoders are not intended to be thread-safe and thus they are allow to
avoid internal locking
- * and reuse internal buffers to improve performance.
+ * == Scala ==
+ * Encoders are generally created automatically though implicits from a
`SQLContext`.
+ *
+ * {{{
+ * import sqlContext.implicits._
+ *
+ * val ds = Seq(1, 2, 3).toDS() // implicitly provided
(sqlContext.implicits.newIntEncoder)
+ * }}}
+ *
+ * == Java ==
+ * Encoders are specified by calling static methods on [[Encoders]].
+ *
+ * {{{
+ * List<String> data = Arrays.asList("abc", "abc", "xyz");
+ * Dataset<String> ds = context.createDataset(data, Encoders.STRING());
+ * }}}
+ *
+ * Encoders can be composed into tuples:
+ *
+ * {{{
+ * Encoder<Tuple2<Integer, String>> encoder2 =
Encoders.tuple(Encoders.INT(), Encoders.STRING());
+ * List<Tuple2<Integer, String>> data2 = Arrays.asList(new
scala.Tuple2(1, "a");
+ * Dataset<Tuple2<Integer, String>> ds2 = context.createDataset(data2,
encoder2);
+ * }}}
+ *
+ * Or constructed from Java Beans:
+ *
+ * {{{
+ * Encoders.bean(MyClass.class);
+ * }}}
+ *
+ * == Implementation ==
+ * - Encoders are not intended to be thread-safe and thus they are
allowed to avoid internal
+ * locking and reuse internal buffers to improve performance.
*
* @since 1.6.0
*/
+@Experimental
+@implicitNotFound("Unable to find encoder for type stored in a Dataset.
Primitive types " +
+ "(Int, String, etc) and Products (case classes) and primitive types are
supported by " +
+ "importing sqlContext.implicits._ Support for serializing other types
will be added in future " +
--- End diff --
@marmbrus Primitive types mentioned twice ? Is it ok ?
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