apache/spark — pull request #3267 by kai-zeng (2014-11-14 19:44:51+00:00)
Title: change Metadata's get method to return Option types

Class org.apache.spark.sql.catalyst.util.Metadata's get methods may throw NoSuchElement exception if the key does not exist, and there is no method for testing the existence of a key.
This PR changes the get methods to return Option types, as the convention in Map.get.