Repository: spark
Updated Branches:
  refs/heads/branch-2.1 0f6862106 -> 1df8020e1


[SPARK-22862] Docs on lazy elimination of columns missing from an encoder

This behavior has confused some users, so lets clarify it.

Author: Michael Armbrust <mich...@databricks.com>

Closes #20048 from marmbrus/datasetAsDocs.

(cherry picked from commit 8df1da396f64bb7fe76d73cd01498fdf3b8ed964)
Signed-off-by: gatorsmile <gatorsm...@gmail.com>


Project: http://git-wip-us.apache.org/repos/asf/spark/repo
Commit: http://git-wip-us.apache.org/repos/asf/spark/commit/1df8020e
Tree: http://git-wip-us.apache.org/repos/asf/spark/tree/1df8020e
Diff: http://git-wip-us.apache.org/repos/asf/spark/diff/1df8020e

Branch: refs/heads/branch-2.1
Commit: 1df8020e1e1bd136b2374471584e110c4bc0d948
Parents: 0f68621
Author: Michael Armbrust <mich...@databricks.com>
Authored: Thu Dec 21 21:38:16 2017 -0800
Committer: gatorsmile <gatorsm...@gmail.com>
Committed: Thu Dec 21 21:38:56 2017 -0800

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 sql/core/src/main/scala/org/apache/spark/sql/Dataset.scala | 4 ++++
 1 file changed, 4 insertions(+)
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http://git-wip-us.apache.org/repos/asf/spark/blob/1df8020e/sql/core/src/main/scala/org/apache/spark/sql/Dataset.scala
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diff --git a/sql/core/src/main/scala/org/apache/spark/sql/Dataset.scala 
b/sql/core/src/main/scala/org/apache/spark/sql/Dataset.scala
index ac34e0b..ecced7c 100644
--- a/sql/core/src/main/scala/org/apache/spark/sql/Dataset.scala
+++ b/sql/core/src/main/scala/org/apache/spark/sql/Dataset.scala
@@ -368,6 +368,10 @@ class Dataset[T] private[sql](
    * If the schema of the Dataset does not match the desired `U` type, you can 
use `select`
    * along with `alias` or `as` to rearrange or rename as required.
    *
+   * Note that `as[]` only changes the view of the data that is passed into 
typed operations,
+   * such as `map()`, and does not eagerly project away any columns that are 
not present in
+   * the specified class.
+   *
    * @group basic
    * @since 1.6.0
    */


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