[SPARK-4693] [SQL] PruningPredicates may be wrong if predicates contains an empty AttributeSet() references

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

@@ -112,4 +112,6 @@ class AttributeSet private (val baseSet: Set[AttributeEquals])
   override def toSeq: Seq[Attribute] = baseSet.map(_.a).toArray.toSeq
 
   override def toString = "{" + baseSet.map(_.a).mkString(", ") + "}"
+
+  override def isEmpty: Boolean = baseSet.isEmpty
 }

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

@@ -194,8 +194,9 @@ private[hive] trait HiveStrategies {
         // Filter out all predicates that only deal with partition keys, these are given to the
         // hive table scan operator to be used for partition pruning.
         val partitionKeyIds = AttributeSet(relation.partitionKeys)
-        val (pruningPredicates, otherPredicates) = predicates.partition {
-          _.references.subsetOf(partitionKeyIds)
+        val (pruningPredicates, otherPredicates) = predicates.partition { predicate =>
+          !predicate.references.isEmpty &&
+          predicate.references.subsetOf(partitionKeyIds)
         }
 
         pruneFilterProject(

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

@@ -413,6 +413,15 @@ class HiveQuerySuite extends HiveComparisonTest with BeforeAndAfter {
   createQueryTest("select null from table",
     "SELECT null FROM src LIMIT 1")
 
+  test("predicates contains an empty AttributeSet() references") {
+    sql(
+      """
+        |SELECT a FROM (
+        |  SELECT 1 AS a FROM src LIMIT 1 ) table
+        |WHERE abs(20141202) is not null
+      """.stripMargin).collect()
+  }
+
   test("implement identity function using case statement") {
     val actual = sql("SELECT (CASE key WHEN key THEN key END) FROM src")
       .map { case Row(i: Int) => i }