[SPARK-2225] Turn HAVING without GROUP BY into WHERE.

@willb

Author: Reynold Xin <rxin@apache.org>

Closes apache#1161 from rxin/having-filter and squashes the following commits:

fa8359a [Reynold Xin] [SPARK-2225] Turn HAVING without GROUP BY into WHERE.

sql/hive/src/main/scala/org/apache/spark/sql/hive/HiveQl.scala

@@ -563,7 +563,6 @@ private[hive] object HiveQl {
             withWhere)
         }.getOrElse(withWhere)
 
-
         // The projection of the query can either be a normal projection, an aggregation
         // (if there is a group by) or a script transformation.
         val withProject = transformation.getOrElse {
@@ -581,16 +580,10 @@ private[hive] object HiveQl {
         val withDistinct =
           if (selectDistinctClause.isDefined) Distinct(withProject) else withProject
 
-        val withHaving = havingClause.map { h => 
-
-          if (groupByClause == None) {
-            throw new SemanticException("HAVING specified without GROUP BY")
-          }
-
-          val havingExpr = h.getChildren.toSeq match {
-            case Seq(hexpr) => nodeToExpr(hexpr)
-          }
-
+        val withHaving = havingClause.map { h =>
+          val havingExpr = h.getChildren.toSeq match { case Seq(hexpr) => nodeToExpr(hexpr) }
+          // Note that we added a cast to boolean. If the expression itself is already boolean,
+          // the optimizer will get rid of the unnecessary cast.
           Filter(Cast(havingExpr, BooleanType), withDistinct)
         }.getOrElse(withDistinct)
 

sql/hive/src/test/scala/org/apache/spark/sql/hive/execution/HiveQuerySuite.scala

@@ -227,27 +227,22 @@ class HiveQuerySuite extends HiveComparisonTest {
   test("SPARK-2180: HAVING support in GROUP BY clauses (positive)") {
     val fixture = List(("foo", 2), ("bar", 1), ("foo", 4), ("bar", 3))
       .zipWithIndex.map {case Pair(Pair(value, attr), key) => HavingRow(key, value, attr)}
-
     TestHive.sparkContext.parallelize(fixture).registerAsTable("having_test")
-
     val results = 
       hql("SELECT value, max(attr) AS attr FROM having_test GROUP BY value HAVING attr > 3")
       .collect()
       .map(x => Pair(x.getString(0), x.getInt(1)))
-    
+
     assert(results === Array(Pair("foo", 4)))
-
     TestHive.reset()
   }
-
-  test("SPARK-2180:  HAVING without GROUP BY raises exception") {
-    intercept[Exception] {
-      hql("SELECT value, attr FROM having_test HAVING attr > 3")
-    }
-  }
 
-  test("SPARK-2180:  HAVING with non-boolean clause raises no exceptions") {
-    val results = hql("select key, count(*) c from src group by key having c").collect()
+  test("SPARK-2180: HAVING with non-boolean clause raises no exceptions") {
+    hql("select key, count(*) c from src group by key having c").collect()
+  }
+
+  test("SPARK-2225: turn HAVING without GROUP BY into a simple filter") {
+    assert(hql("select key from src having key > 490").collect().size < 100)
   }
 
   test("Query Hive native command execution result") {