Refactor code and update test cases.

Author: yhuai

sql/core/src/main/scala/org/apache/spark/sql/json/JSONRelation.scala

@@ -26,7 +26,7 @@ private[sql] class DefaultSource extends SchemaRelationProvider {
   override def createRelation(
       sqlContext: SQLContext,
       parameters: Map[String, String],
-      schema: Option[StructType] = None): BaseRelation = {
+      schema: Option[StructType]): BaseRelation = {
     val fileName = parameters.getOrElse("path", sys.error("Option 'path' not specified"))
     val samplingRatio = parameters.get("samplingRatio").map(_.toDouble).getOrElse(1.0)
 

sql/core/src/main/scala/org/apache/spark/sql/parquet/newParquet.scala

@@ -48,7 +48,7 @@ class DefaultSource extends SchemaRelationProvider {
   override def createRelation(
       sqlContext: SQLContext,
       parameters: Map[String, String],
-      schema: Option[StructType] = None): BaseRelation = {
+      schema: Option[StructType]): BaseRelation = {
     val path =
       parameters.getOrElse("path", sys.error("'path' must be specified for parquet tables."))
 

sql/core/src/main/scala/org/apache/spark/sql/sources/ddl.scala

@@ -64,14 +64,14 @@ private[sql] class DDLParser extends StandardTokenParsers with PackratParsers wi
 
   // Data types.
   protected val STRING = Keyword("STRING")
-  protected val FLOAT = Keyword("FLOAT")
-  protected val INT = Keyword("INT")
+  protected val BINARY = Keyword("BINARY")
+  protected val BOOLEAN = Keyword("BOOLEAN")
   protected val TINYINT = Keyword("TINYINT")
   protected val SMALLINT = Keyword("SMALLINT")
-  protected val DOUBLE = Keyword("DOUBLE")
+  protected val INT = Keyword("INT")
   protected val BIGINT = Keyword("BIGINT")
-  protected val BINARY = Keyword("BINARY")
-  protected val BOOLEAN = Keyword("BOOLEAN")
+  protected val FLOAT = Keyword("FLOAT")
+  protected val DOUBLE = Keyword("DOUBLE")
   protected val DECIMAL = Keyword("DECIMAL")
   protected val DATE = Keyword("DATE")
   protected val TIMESTAMP = Keyword("TIMESTAMP")
@@ -105,8 +105,8 @@ private[sql] class DDLParser extends StandardTokenParsers with PackratParsers wi
     CREATE ~ TEMPORARY ~ TABLE ~> ident
       ~ (tableCols).? ~ (USING ~> className) ~ (OPTIONS ~> options) ^^ {
       case tableName ~ columns ~ provider ~ opts =>
-        val tblColumns = if(columns.isEmpty) Seq.empty else columns.get
-        CreateTableUsing(tableName, tblColumns, provider, opts)
+        val userSpecifiedSchema = columns.flatMap(fields => Some(StructType(fields)))
+        CreateTableUsing(tableName, userSpecifiedSchema, provider, opts)
     }
   )
 
@@ -184,7 +184,7 @@ private[sql] class DDLParser extends StandardTokenParsers with PackratParsers wi
 
 private[sql] case class CreateTableUsing(
     tableName: String,
-    tableCols: Seq[StructField],
+    userSpecifiedSchema: Option[StructType],
     provider: String,
     options: Map[String, String]) extends RunnableCommand {
 
@@ -203,16 +203,9 @@ private[sql] case class CreateTableUsing(
           .asInstanceOf[org.apache.spark.sql.sources.RelationProvider]
           .createRelation(sqlContext, new CaseInsensitiveMap(options))
       case dataSource: org.apache.spark.sql.sources.SchemaRelationProvider =>
-        if(tableCols.isEmpty) {
-          dataSource
-            .asInstanceOf[org.apache.spark.sql.sources.SchemaRelationProvider]
-            .createRelation(sqlContext, new CaseInsensitiveMap(options))
-        } else {
-          dataSource
-            .asInstanceOf[org.apache.spark.sql.sources.SchemaRelationProvider]
-            .createRelation(
-              sqlContext, new CaseInsensitiveMap(options), Some(StructType(tableCols)))
-        }
+        dataSource
+          .asInstanceOf[org.apache.spark.sql.sources.SchemaRelationProvider]
+          .createRelation(sqlContext, new CaseInsensitiveMap(options), userSpecifiedSchema)
     }
 
     sqlContext.baseRelationToSchemaRDD(relation).registerTempTable(tableName)

sql/core/src/main/scala/org/apache/spark/sql/sources/interfaces.scala

@@ -68,7 +68,7 @@ trait SchemaRelationProvider {
   def createRelation(
       sqlContext: SQLContext,
       parameters: Map[String, String],
-      schema: Option[StructType] = None): BaseRelation
+      schema: Option[StructType]): BaseRelation
 }
 
 /**