[SPARK-15677][SQL] Query with scalar sub-query in the SELECT list throws UnsupportedOperationException

## What changes were proposed in this pull request?
Queries with scalar sub-query in the SELECT list run against a local, in-memory relation throw
UnsupportedOperationException exception.

Problem repro:
```SQL
scala> Seq((1, 1), (2, 2)).toDF("c1", "c2").createOrReplaceTempView("t1")
scala> Seq((1, 1), (2, 2)).toDF("c1", "c2").createOrReplaceTempView("t2")
scala> sql("select (select min(c1) from t2) from t1").show()

java.lang.UnsupportedOperationException: Cannot evaluate expression: scalar-subquery#62 []
  at org.apache.spark.sql.catalyst.expressions.Unevaluable$class.eval(Expression.scala:215)
  at org.apache.spark.sql.catalyst.expressions.ScalarSubquery.eval(subquery.scala:62)
  at org.apache.spark.sql.catalyst.expressions.Alias.eval(namedExpressions.scala:142)
  at org.apache.spark.sql.catalyst.expressions.InterpretedProjection.apply(Projection.scala:45)
  at org.apache.spark.sql.catalyst.expressions.InterpretedProjection.apply(Projection.scala:29)
  at scala.collection.TraversableLike$$anonfun$map$1.apply(TraversableLike.scala:234)
  at scala.collection.TraversableLike$$anonfun$map$1.apply(TraversableLike.scala:234)
  at scala.collection.immutable.List.foreach(List.scala:381)
  at scala.collection.TraversableLike$class.map(TraversableLike.scala:234)
  at scala.collection.immutable.List.map(List.scala:285)
  at org.apache.spark.sql.catalyst.optimizer.ConvertToLocalRelation$$anonfun$apply$37.applyOrElse(Optimizer.scala:1473)
```
The problem is specific to local, in memory relations. It is caused by rule ConvertToLocalRelation, which attempts to push down
a scalar-subquery expression to the local tables.

The solution prevents the rule to apply if Project references scalar subqueries.

## How was this patch tested?
Added regression tests to SubquerySuite.scala

Author: Ioana Delaney <ioanamdelaney@gmail.com>

Closes #13418 from ioana-delaney/scalarSubV2.

1 files changed, 6 insertions, 1 deletions

diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
index 11cd84b396..1e10d73a4b 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/optimizer/Optimizer.scala
@@ -1511,10 +1511,15 @@ object DecimalAggregates extends Rule[LogicalPlan] {
  */
 object ConvertToLocalRelation extends Rule[LogicalPlan] {
   def apply(plan: LogicalPlan): LogicalPlan = plan transform {
-    case Project(projectList, LocalRelation(output, data)) =>
+    case Project(projectList, LocalRelation(output, data))
+        if !projectList.exists(hasUnevaluableExpr) =>
       val projection = new InterpretedProjection(projectList, output)
       LocalRelation(projectList.map(_.toAttribute), data.map(projection))
   }
+
+  private def hasUnevaluableExpr(expr: Expression): Boolean = {
+    expr.find(e => e.isInstanceOf[Unevaluable] && !e.isInstanceOf[AttributeReference]).isDefined
+  }
 }
 
 /**