[GitHub] [spark] JoshRosen commented on a diff in pull request #37460: [SPARK-40031][SQL] Remove unnecessary TryEval in TryCast

[GitBox <gi...@apache.org>]

JoshRosen commented on code in PR #37460:
URL: https://github.com/apache/spark/pull/37460#discussion_r942069508


##########
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/TryEval.scala:
##########
@@ -91,7 +91,16 @@ case class TryCast(child: Expression, toType: DataType, timeZoneId: Option[Strin
     (!Cast.needsTimeZone(child.dataType, toType) || timeZoneId.isDefined)
 
   override lazy val replacement = {
-    TryEval(Cast(child, toType, timeZoneId = timeZoneId, ansiEnabled = true))
+    if (equivalentToNonAnsiCast) {
+      Cast(child, toType, timeZoneId = timeZoneId, ansiEnabled = false)
+    } else {
+      TryEval(Cast(child, toType, timeZoneId = timeZoneId, ansiEnabled = true))
+    }
+  }
+
+  private def equivalentToNonAnsiCast: Boolean = {
+    val fromType = child.dataType
+    canUpCast(fromType, toType) || fromType == StringType

Review Comment:
   Should this be 
   
   ```suggestion
       canUpCast(fromType, toType) || toType == StringType
   ```
   ?
   
   We can cast anything to a string but we can't cast arbitrary strings to arbitrary types.



##########
sql/catalyst/src/test/scala/org/apache/spark/sql/catalyst/expressions/TryCastSuite.scala:
##########
@@ -39,8 +39,8 @@ class TryCastSuite extends SparkFunSuite {
   }
 
   test("nullability") {
-    assert(cast("abcdef", StringType).nullable)
-    assert(cast("abcdef", BinaryType).nullable)
+    assert(!cast("abcdef", StringType).nullable)
+    assert(!cast("abcdef", BinaryType).nullable)

Review Comment:
   Should we also add a test case which _is_ expected to be nullable? Maybe something like `cast("abcdef", IntegerType)`?



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