[GitHub] [spark] cloud-fan commented on a diff in pull request #37486: [SPARK-40054][SQL] Restore the error handling syntax of try_cast()

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

cloud-fan commented on code in PR #37486:
URL: https://github.com/apache/spark/pull/37486#discussion_r944151962


##########
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/Cast.scala:
##########
@@ -460,29 +500,57 @@ case class Cast(
 
   final override def nodePatternsInternal(): Seq[TreePattern] = Seq(CAST)
 
-  private def typeCheckFailureMessage: String = if (ansiEnabled) {
-    if (getTagValue(Cast.BY_TABLE_INSERTION).isDefined) {
-      Cast.typeCheckFailureMessage(child.dataType, dataType,
-        Some(SQLConf.STORE_ASSIGNMENT_POLICY.key -> SQLConf.StoreAssignmentPolicy.LEGACY.toString))
-    } else {
-      Cast.typeCheckFailureMessage(child.dataType, dataType,
-        Some(SQLConf.ANSI_ENABLED.key -> "false"))
-    }
-  } else {
-    s"cannot cast ${child.dataType.catalogString} to ${dataType.catalogString}"
+  def ansiEnabled: Boolean = {
+    evalMode == EvalMode.ANSI || evalMode == EvalMode.TRY
+  }
+
+  // Whether this expression is used for `try_cast()`.
+  def isTryCast: Boolean = {
+    evalMode == EvalMode.TRY
+  }
+
+  private def typeCheckFailureMessage: String = evalMode match {
+    case EvalMode.ANSI =>
+      if (getTagValue(Cast.BY_TABLE_INSERTION).isDefined) {
+        Cast.typeCheckFailureMessage(child.dataType, dataType,
+          Some(SQLConf.STORE_ASSIGNMENT_POLICY.key ->
+            SQLConf.StoreAssignmentPolicy.LEGACY.toString))
+      } else {
+        Cast.typeCheckFailureMessage(child.dataType, dataType,
+          Some(SQLConf.ANSI_ENABLED.key -> "false"))
+      }
+    case EvalMode.TRY =>
+      Cast.typeCheckFailureMessage(child.dataType, dataType, None)
+    case _ =>
+      s"cannot cast ${child.dataType.catalogString} to ${dataType.catalogString}"
   }
 
   override def checkInputDataTypes(): TypeCheckResult = {
-    if (ansiEnabled && Cast.canAnsiCast(child.dataType, dataType)) {
-      TypeCheckResult.TypeCheckSuccess
-    } else if (!ansiEnabled && Cast.canCast(child.dataType, dataType)) {
+    val canCast = evalMode match {
+      case EvalMode.LEGACY => Cast.canCast(child.dataType, dataType)
+      case EvalMode.ANSI => Cast.canAnsiCast(child.dataType, dataType)
+      case EvalMode.TRY => Cast.canTryCast(child.dataType, dataType)
+      case other => throw new IllegalArgumentException(s"Unknown EvalMode value: $other")
+    }
+    if (canCast) {
       TypeCheckResult.TypeCheckSuccess
     } else {
       TypeCheckResult.TypeCheckFailure(typeCheckFailureMessage)
     }
   }
 
-  override def nullable: Boolean = child.nullable || Cast.forceNullable(child.dataType, dataType)
+  override def nullable: Boolean = if (!isTryCast) {
+    child.nullable || Cast.forceNullable(child.dataType, dataType)
+  } else {
+    (child.dataType, dataType) match {

Review Comment:
   is this new?



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