[SPARK-7964][SQL] remove unnecessary type coercion rule

We have defined these logics in `Cast` already, I think we should remove this rule.

Author: Wenchen Fan <cloud0fan@outlook.com>

Closes #6516 from cloud-fan/tmp2 and squashes the following commits:

d5035a4 [Wenchen Fan] remove useless rule

3 files changed, 2 insertions, 43 deletions

diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/HiveTypeCoercion.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/HiveTypeCoercion.scala
index 44664f898f..195418d6df 100644
--- a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/HiveTypeCoercion.scala
+++ b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/HiveTypeCoercion.scala
@@ -77,7 +77,6 @@ trait HiveTypeCoercion {
     PromoteStrings ::
     DecimalPrecision ::
     BooleanComparisons ::
-    BooleanCasts ::
     StringToIntegralCasts ::
     FunctionArgumentConversion ::
     CaseWhenCoercion ::
@@ -511,32 +510,6 @@ trait HiveTypeCoercion {
   }
 
   /**
-   * Casts to/from [[BooleanType]] are transformed into comparisons since
-   * the JVM does not consider Booleans to be numeric types.
-   */
-  object BooleanCasts extends Rule[LogicalPlan] {
-    def apply(plan: LogicalPlan): LogicalPlan = plan transformAllExpressions {
-      // Skip nodes who's children have not been resolved yet.
-      case e if !e.childrenResolved => e
-      // Skip if the type is boolean type already. Note that this extra cast should be removed
-      // by optimizer.SimplifyCasts.
-      case Cast(e, BooleanType) if e.dataType == BooleanType => e
-      // DateType should be null if be cast to boolean.
-      case Cast(e, BooleanType) if e.dataType == DateType => Cast(e, BooleanType)
-      // If the data type is not boolean and is being cast boolean, turn it into a comparison
-      // with the numeric value, i.e. x != 0. This will coerce the type into numeric type.
-      case Cast(e, BooleanType) if e.dataType != BooleanType => Not(EqualTo(e, Literal(0)))
-      // Stringify boolean if casting to StringType.
-      // TODO Ensure true/false string letter casing is consistent with Hive in all cases.
-      case Cast(e, StringType) if e.dataType == BooleanType =>
-        If(e, Literal("true"), Literal("false"))
-      // Turn true into 1, and false into 0 if casting boolean into other types.
-      case Cast(e, dataType) if e.dataType == BooleanType =>
-        Cast(If(e, Literal(1), Literal(0)), dataType)
-    }
-  }
-
-  /**
    * When encountering a cast from a string representing a valid fractional number to an integral
    * type the jvm will throw a `java.lang.NumberFormatException`.  Hive, in contrast, returns the
    * truncated version of this number.
diff --git a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/analysis/HiveTypeCoercionSuite.scala b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/analysis/HiveTypeCoercionSuite.scala
index fcd745f43c..f0101f4a88 100644
--- a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/analysis/HiveTypeCoercionSuite.scala
+++ b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/analysis/HiveTypeCoercionSuite.scala
@@ -104,22 +104,6 @@ class HiveTypeCoercionSuite extends PlanTest {
     widenTest(ArrayType(IntegerType), StructType(Seq()), None)
   }
 
-  test("boolean casts") {
-    val booleanCasts = new HiveTypeCoercion { }.BooleanCasts
-    def ruleTest(initial: Expression, transformed: Expression) {
-      val testRelation = LocalRelation(AttributeReference("a", IntegerType)())
-      comparePlans(
-        booleanCasts(Project(Seq(Alias(initial, "a")()), testRelation)),
-        Project(Seq(Alias(transformed, "a")()), testRelation))
-    }
-    // Remove superflous boolean -> boolean casts.
-    ruleTest(Cast(Literal(true), BooleanType), Literal(true))
-    // Stringify boolean when casting to string.
-    ruleTest(
-      Cast(Literal(false), StringType),
-      If(Literal(false), Literal("true"), Literal("false")))
-  }
-
   test("coalesce casts") {
     val fac = new HiveTypeCoercion { }.FunctionArgumentConversion
     def ruleTest(initial: Expression, transformed: Expression) {
diff --git a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/expressions/ExpressionEvaluationSuite.scala b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/expressions/ExpressionEvaluationSuite.scala
index b511aa3a24..10181366c2 100644
--- a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/expressions/ExpressionEvaluationSuite.scala
+++ b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/expressions/ExpressionEvaluationSuite.scala
@@ -372,6 +372,8 @@ class ExpressionEvaluationSuite extends ExpressionEvaluationBaseSuite {
       DecimalType.Unlimited, ByteType), TimestampType), LongType), StringType), ShortType), 0)
     checkEvaluation(Literal(true) cast IntegerType, 1)
     checkEvaluation(Literal(false) cast IntegerType, 0)
+    checkEvaluation(Literal(true) cast StringType, "true")
+    checkEvaluation(Literal(false) cast StringType, "false")
     checkEvaluation(Cast(Literal(1) cast BooleanType, IntegerType), 1)
     checkEvaluation(Cast(Literal(0) cast BooleanType, IntegerType), 0)
     checkEvaluation("23" cast DoubleType, 23d)