fix type coercion when promting to StringType

apache · Apr 15, 2018 · 803a6a4 · 803a6a4
1 parent 73f2853
commit 803a6a4
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Showing 2 changed files with 12 additions and 1 deletion.
diff --git a/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/TypeCoercion.scala b/sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/analysis/TypeCoercion.scala
@@ -178,7 +178,13 @@ object TypeCoercion {
   private def findWiderCommonType(types: Seq[DataType]): Option[DataType] = {
     types.foldLeft[Option[DataType]](Some(NullType))((r, c) => r match {
       case Some(d) => findWiderTypeForTwo(d, c)
-      case None => None
+      // Currently we find the wider common type by comparing the two types from left to right,
+      // this can be a problem when you have two data types which don't have a common type but each
+      // can be promoted to StringType. For instance, (TimestampType, IntegerType, StringType)
+      // should have StringType as the wider common type.
+      case None if types.exists(_ == StringType) &&
+        types.forall(stringPromotion(_, StringType).nonEmpty) => Some(StringType)
+      case _ => None
     })
   }
 

diff --git a/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/analysis/TypeCoercionSuite.scala b/sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/analysis/TypeCoercionSuite.scala
@@ -572,6 +572,11 @@ class TypeCoercionSuite extends AnalysisTest {
       Coalesce(Seq(nullLit, floatNullLit, doubleLit, stringLit)),
       Coalesce(Seq(Cast(nullLit, StringType), Cast(floatNullLit, StringType),
         Cast(doubleLit, StringType), Cast(stringLit, StringType))))
+
+    ruleTest(rule,
+      Coalesce(Seq(timestampLit, intLit, stringLit)),
+      Coalesce(Seq(Cast(timestampLit, StringType), Cast(intLit, StringType),
+        Cast(stringLit, StringType))))
   }
 
   test("CreateArray casts") {