Github user marmbrus commented on a diff in the pull request:
https://github.com/apache/spark/pull/3431#discussion_r22742665
--- Diff:
sql/core/src/main/scala/org/apache/spark/sql/sources/interfaces.scala ---
@@ -46,6 +46,33 @@ trait RelationProvider {
/**
* ::DeveloperApi::
+ * Implemented by objects that produce relations for a specific kind of
data source. When
+ * Spark SQL is given a DDL operation with
+ * 1. USING clause: to specify the implemented SchemaRelationProvider
+ * 2. User defined schema: users can define schema optionally when create
table
+ *
+ * Users may specify the fully qualified class name of a given data
source. When that class is
+ * not found Spark SQL will append the class name `DefaultSource` to the
path, allowing for
+ * less verbose invocation. For example, 'org.apache.spark.sql.json'
would resolve to the
+ * data source 'org.apache.spark.sql.json.DefaultSource'
+ *
+ * A new instance of this class with be instantiated each time a DDL call
is made.
+ */
+@DeveloperApi
+trait SchemaRelationProvider {
+ /**
+ * Returns a new base relation with the given parameters and user
defined schema.
+ * Note: the parameters' keywords are case insensitive and this
insensitivity is enforced
+ * by the Map that is passed to the function.
+ */
+ def createRelation(
+ sqlContext: SQLContext,
+ parameters: Map[String, String],
+ schema: Option[StructType]): BaseRelation
--- End diff --
Why is this an option? we have two traits and option is not very friendly
to java
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