Don't check children resolved for UDF resolution.

Author: rxin

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/SqlParser.scala

@@ -68,7 +68,6 @@ class SqlParser extends AbstractSparkSQLParser with DataTypeParser {
   protected val FULL = Keyword("FULL")
   protected val GROUP = Keyword("GROUP")
   protected val HAVING = Keyword("HAVING")
-  protected val IF = Keyword("IF")
   protected val IN = Keyword("IN")
   protected val INNER = Keyword("INNER")
   protected val INSERT = Keyword("INSERT")
@@ -277,6 +276,7 @@ class SqlParser extends AbstractSparkSQLParser with DataTypeParser {
       lexical.normalizeKeyword(udfName) match {
         case "sum" => SumDistinct(exprs.head)
         case "count" => CountDistinct(exprs)
+        case _ => throw new AnalysisException(s"function $udfName does not support DISTINCT")
       }
     }
     | APPROXIMATE ~> ident ~ ("(" ~ DISTINCT ~> expression <~ ")") ^^ { case udfName ~ exp =>

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/Analyzer.scala

@@ -460,7 +460,7 @@ class Analyzer(
     def apply(plan: LogicalPlan): LogicalPlan = plan transform {
       case q: LogicalPlan =>
         q transformExpressions {
-          case u @ UnresolvedFunction(name, children) if u.childrenResolved =>
+          case u @ UnresolvedFunction(name, children) =>
             withPosition(u) {
               registry.lookupFunction(name, children)
             }
@@ -494,20 +494,21 @@ class Analyzer(
   object UnresolvedHavingClauseAttributes extends Rule[LogicalPlan] {
     def apply(plan: LogicalPlan): LogicalPlan = plan transformUp {
       case filter @ Filter(havingCondition, aggregate @ Aggregate(_, originalAggExprs, _))
-          if aggregate.resolved && containsAggregate(havingCondition) => {
+          if aggregate.resolved && containsAggregate(havingCondition) =>
+
         val evaluatedCondition = Alias(havingCondition, "havingCondition")()
         val aggExprsWithHaving = evaluatedCondition +: originalAggExprs
 
         Project(aggregate.output,
           Filter(evaluatedCondition.toAttribute,
             aggregate.copy(aggregateExpressions = aggExprsWithHaving)))
-      }
     }
 
-    protected def containsAggregate(condition: Expression): Boolean =
+    protected def containsAggregate(condition: Expression): Boolean = {
       condition
         .collect { case ae: AggregateExpression => ae }
         .nonEmpty
+    }
   }
 
   /**

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/Expression.scala

@@ -25,10 +25,10 @@ import org.apache.spark.sql.types._
 
 
 /**
- * For Catalyst to work correctly, concrete implementations of [[Expression]]s must be case classes
- * whose constructor arguments are all Expressions types. In addition, if we want to support more
- * than one constructor, define those constructors explicitly as apply methods in the companion
- * object.
+ * If an expression wants to be exposed in the function registry (so users can call it with
+ * "name(arguments...)", the concrete implementation must be a case class whose constructor
+ * arguments are all Expressions types. In addition, if it needs to support more than one
+ * constructor, define those constructors explicitly as apply methods in the companion object.
  *
  * See [[Substring]] for an example.
  */