[SPARK-5868][SQL] Fix python UDFs in HiveContext and checks in SQLContext

Author: Michael Armbrust <michael@databricks.com>

Closes #4657 from marmbrus/pythonUdfs and squashes the following commits:

a7823a8 [Michael Armbrust] [SPARK-5868][SQL] Fix python UDFs in HiveContext and checks in SQLContext

sql/core/src/main/scala/org/apache/spark/sql/SQLContext.scala

@@ -113,6 +113,7 @@ class SQLContext(@transient val sparkContext: SparkContext)
   protected[sql] lazy val analyzer: Analyzer =
     new Analyzer(catalog, functionRegistry, caseSensitive = true) {
       override val extendedResolutionRules =
+        ExtractPythonUdfs ::
         sources.PreWriteCheck(catalog) ::
         sources.PreInsertCastAndRename ::
         Nil
@@ -1059,7 +1060,7 @@ class SQLContext(@transient val sparkContext: SparkContext)
   @DeveloperApi
   protected[sql] class QueryExecution(val logical: LogicalPlan) {
 
-    lazy val analyzed: LogicalPlan = ExtractPythonUdfs(analyzer(logical))
+    lazy val analyzed: LogicalPlan = analyzer(logical)
     lazy val withCachedData: LogicalPlan = cacheManager.useCachedData(analyzed)
     lazy val optimizedPlan: LogicalPlan = optimizer(withCachedData)
 

sql/core/src/main/scala/org/apache/spark/sql/execution/pythonUdfs.scala

@@ -205,6 +205,9 @@ case class EvaluatePython(
   extends logical.UnaryNode {
 
   def output = child.output :+ resultAttribute
+
+  // References should not include the produced attribute.
+  override def references = udf.references
 }
 
 /**