[SPARK-17100] [SQL] fix Python udf in filter on top of outer join

## What changes were proposed in this pull request?

In optimizer, we try to evaluate the condition to see whether it's nullable or not, but some expressions are not evaluable, we should check that before evaluate it.

## How was this patch tested?

Added regression tests.

Author: Davies Liu <davies@databricks.com>

Closes #15103 from davies/udf_join.

python/pyspark/sql/tests.py

@@ -328,6 +328,14 @@ class SQLTests(ReusedPySparkTestCase):
         [row] = self.spark.sql("SELECT double(add(1, 2)), add(double(2), 1)").collect()
         self.assertEqual(tuple(row), (6, 5))
 
+    def test_udf_in_filter_on_top_of_outer_join(self):
+        from pyspark.sql.functions import udf
+        left = self.spark.createDataFrame([Row(a=1)])
+        right = self.spark.createDataFrame([Row(a=1)])
+        df = left.join(right, on='a', how='left_outer')
+        df = df.withColumn('b', udf(lambda x: 'x')(df.a))
+        self.assertEqual(df.filter('b = "x"').collect(), [Row(a=1, b='x')])
+
     def test_udf_without_arguments(self):
         self.spark.catalog.registerFunction("foo", lambda: "bar")
         [row] = self.spark.sql("SELECT foo()").collect()

sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/joins.scala

@@ -109,7 +109,9 @@ object EliminateOuterJoin extends Rule[LogicalPlan] with PredicateHelper {
     if (!e.deterministic || SubqueryExpression.hasCorrelatedSubquery(e)) return false
     val attributes = e.references.toSeq
     val emptyRow = new GenericInternalRow(attributes.length)
-    val v = BindReferences.bindReference(e, attributes).eval(emptyRow)
+    val boundE = BindReferences.bindReference(e, attributes)
+    if (boundE.find(_.isInstanceOf[Unevaluable]).isDefined) return false
+    val v = boundE.eval(emptyRow)
     v == null || v == false
   }