[SPARK-10083] [SQL] CaseWhen should support type coercion of DecimalType and FractionalType

create t1 (a decimal(7, 2), b long);
select case when 1=1 then a else 1.0 end from t1;
select case when 1=1 then a else b end from t1;

Author: Daoyuan Wang <daoyuan.wang@intel.com>

Closes #8270 from adrian-wang/casewhenfractional.

2 files changed, 13 insertions, 2 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 62c27ee0b9..f2f2ba2f96 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
@@ -605,7 +605,7 @@ object HiveTypeCoercion {
     def apply(plan: LogicalPlan): LogicalPlan = plan resolveExpressions {
       case c: CaseWhenLike if c.childrenResolved && !c.valueTypesEqual =>
         logDebug(s"Input values for null casting ${c.valueTypes.mkString(",")}")
-        val maybeCommonType = findTightestCommonTypeAndPromoteToString(c.valueTypes)
+        val maybeCommonType = findWiderCommonType(c.valueTypes)
         maybeCommonType.map { commonType =>
           val castedBranches = c.branches.grouped(2).map {
             case Seq(when, value) if value.dataType != commonType =>
@@ -622,7 +622,7 @@ object HiveTypeCoercion {
 
       case c: CaseKeyWhen if c.childrenResolved && !c.resolved =>
         val maybeCommonType =
-          findTightestCommonTypeAndPromoteToString((c.key +: c.whenList).map(_.dataType))
+          findWiderCommonType((c.key +: c.whenList).map(_.dataType))
         maybeCommonType.map { commonType =>
           val castedBranches = c.branches.grouped(2).map {
             case Seq(whenExpr, thenExpr) if whenExpr.dataType != commonType =>
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 cbdf453f60..6f33ab733b 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
@@ -285,6 +285,17 @@ class HiveTypeCoercionSuite extends PlanTest {
       CaseKeyWhen(Literal(true), Seq(Literal(1), Literal("a"))),
       CaseKeyWhen(Literal(true), Seq(Literal(1), Literal("a")))
     )
+    ruleTest(HiveTypeCoercion.CaseWhenCoercion,
+      CaseWhen(Seq(Literal(true), Literal(1.2), Literal.create(1, DecimalType(7, 2)))),
+      CaseWhen(Seq(
+        Literal(true), Literal(1.2), Cast(Literal.create(1, DecimalType(7, 2)), DoubleType)))
+    )
+    ruleTest(HiveTypeCoercion.CaseWhenCoercion,
+      CaseWhen(Seq(Literal(true), Literal(100L), Literal.create(1, DecimalType(7, 2)))),
+      CaseWhen(Seq(
+        Literal(true), Cast(Literal(100L), DecimalType(22, 2)),
+        Cast(Literal.create(1, DecimalType(7, 2)), DecimalType(22, 2))))
+    )
   }
 
   test("type coercion simplification for equal to") {