[SPARK-7437] [SQL] Fold "literal in (item1, item2, ..., literal, ...)" into true or false directly

SQL
```
select key from src where 3 in (4, 5);
```
Before
```
== Optimized Logical Plan ==
Project [key#12]
 Filter 3 INSET (5,4)
  MetastoreRelation default, src, None
```

After
```
== Optimized Logical Plan ==
LocalRelation [key#228], []
```

Author: Zhongshuai Pei <[email protected]>
Author: DoingDone9 <[email protected]>

Closes apache#5972 from DoingDone9/InToFalse and squashes the following commits:

4c722a2 [Zhongshuai Pei] Update predicates.scala
abe2bbb [Zhongshuai Pei] Update Optimizer.scala
fa461a5 [Zhongshuai Pei] Update Optimizer.scala
e34c28a [Zhongshuai Pei] Update predicates.scala
24739bd [Zhongshuai Pei] Update ConstantFoldingSuite.scala
f4dbf50 [Zhongshuai Pei] Update ConstantFoldingSuite.scala
35ceb7a [Zhongshuai Pei] Update Optimizer.scala
36c194e [Zhongshuai Pei] Update Optimizer.scala
2e8f6ca [Zhongshuai Pei] Update Optimizer.scala
14952e2 [Zhongshuai Pei] Merge pull request #13 from apache/master
f03fe7f [Zhongshuai Pei] Merge pull request #12 from apache/master
f12fa50 [Zhongshuai Pei] Merge pull request #10 from apache/master
f61210c [Zhongshuai Pei] Merge pull request #9 from apache/master
34b1a9a [Zhongshuai Pei] Merge pull request #8 from apache/master
802261c [DoingDone9] Merge pull request #7 from apache/master
d00303b [DoingDone9] Merge pull request #6 from apache/master
98b134f [DoingDone9] Merge pull request #5 from apache/master
161cae3 [DoingDone9] Merge pull request #4 from apache/master
c87e8b6 [DoingDone9] Merge pull request #3 from apache/master
cb1852d [DoingDone9] Merge pull request #2 from apache/master
c3f046f [DoingDone9] Merge pull request #1 from apache/master

Author: pzzs

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

@@ -110,6 +110,7 @@ case class InSet(value: Expression, hset: Set[Any])
 
   override def children: Seq[Expression] = value :: Nil
 
+  override def foldable: Boolean = value.foldable
   override def nullable: Boolean = true // TODO: Figure out correct nullability semantics of IN.
   override def toString: String = s"$value INSET ${hset.mkString("(", ",", ")")}"
 

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

@@ -46,13 +46,13 @@ object DefaultOptimizer extends Optimizer {
       CombineLimits) ::
     Batch("ConstantFolding", FixedPoint(100),
       NullPropagation,
+      OptimizeIn,
       ConstantFolding,
       LikeSimplification,
       BooleanSimplification,
       SimplifyFilters,
       SimplifyCasts,
-      SimplifyCaseConversionExpressions,
-      OptimizeIn) ::
+      SimplifyCaseConversionExpressions) ::
     Batch("Decimal Optimizations", FixedPoint(100),
       DecimalAggregates) ::
     Batch("LocalRelation", FixedPoint(100),

sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/optimizer/ConstantFoldingSuite.scala

@@ -35,6 +35,7 @@ class ConstantFoldingSuite extends PlanTest {
       Batch("AnalysisNodes", Once,
         EliminateSubQueries) ::
       Batch("ConstantFolding", Once,
+        OptimizeIn,
         ConstantFolding,
         BooleanSimplification) :: Nil
   }
@@ -247,4 +248,36 @@ class ConstantFoldingSuite extends PlanTest {
 
     comparePlans(optimized, correctAnswer)
   }
+  
+  test("Constant folding test: Fold In(v, list) into true or false") {
+    var originalQuery =
+      testRelation
+        .select('a)
+        .where(In(Literal(1), Seq(Literal(1), Literal(2))))
+
+    var optimized = Optimize.execute(originalQuery.analyze)
+
+    var correctAnswer =
+      testRelation
+        .select('a)
+        .where(Literal(true))
+        .analyze
+
+    comparePlans(optimized, correctAnswer)
+
+    originalQuery =
+      testRelation
+        .select('a)
+        .where(In(Literal(1), Seq(Literal(1), 'a.attr)))
+
+    optimized = Optimize.execute(originalQuery.analyze)
+
+    correctAnswer =
+      testRelation
+        .select('a)
+        .where(Literal(true))
+        .analyze
+
+    comparePlans(optimized, correctAnswer)
+  }
 }