[GitHub] [spark] cloud-fan commented on a diff in pull request #36531: [SPARK-39171][SQL] Unify the Cast expression

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

cloud-fan commented on code in PR #36531:
URL: https://github.com/apache/spark/pull/36531#discussion_r872466512


##########
sql/catalyst/src/main/scala/org/apache/spark/sql/catalyst/expressions/Cast.scala:
##########
@@ -275,6 +376,53 @@ object Cast {
       case _ => null
     }
   }
+
+  // Show suggestion on how to complete the disallowed explicit casting with built-in type
+  // conversion functions.
+  private def suggestionOnConversionFunctions (
+      from: DataType,
+      to: DataType,
+      functionNames: String): String = {
+    // scalastyle:off line.size.limit
+    s"""cannot cast ${from.catalogString} to ${to.catalogString}.
+       |To convert values from ${from.catalogString} to ${to.catalogString}, you can use $functionNames instead.
+       |""".stripMargin
+    // scalastyle:on line.size.limit
+  }
+
+  def typeCheckFailureMessage(
+      from: DataType,
+      to: DataType,
+      fallbackConfKey: Option[String],
+      fallbackConfValue: Option[String]): String =
+    (from, to) match {
+      case (_: NumericType, TimestampType) =>
+        suggestionOnConversionFunctions(from, to,
+          "functions TIMESTAMP_SECONDS/TIMESTAMP_MILLIS/TIMESTAMP_MICROS")
+
+      case (TimestampType, _: NumericType) =>
+        suggestionOnConversionFunctions(from, to, "functions UNIX_SECONDS/UNIX_MILLIS/UNIX_MICROS")
+
+      case (_: NumericType, DateType) =>
+        suggestionOnConversionFunctions(from, to, "function DATE_FROM_UNIX_DATE")
+
+      case (DateType, _: NumericType) =>
+        suggestionOnConversionFunctions(from, to, "function UNIX_DATE")
+
+      // scalastyle:off line.size.limit
+      case _ if fallbackConfKey.isDefined && fallbackConfValue.isDefined && Cast.canCast(from, to) =>
+        s"""
+           | cannot cast ${from.catalogString} to ${to.catalogString} with ANSI mode on.
+           | If you have to cast ${from.catalogString} to ${to.catalogString}, you can set ${fallbackConfKey.get} as ${fallbackConfValue.get}.
+           |""".stripMargin
+      // scalastyle:on line.size.limit
+
+      case _ => s"cannot cast ${from.catalogString} to ${to.catalogString}"
+    }
+
+  def ansiCast(child: Expression, dataType: DataType, timeZoneId: Option[String] = None): Cast =
+    Cast(child, dataType, timeZoneId, true,
+      SQLConf.STORE_ASSIGNMENT_POLICY.key, SQLConf.StoreAssignmentPolicy.LEGACY.toString)
 }
 
 abstract class CastBase extends UnaryExpression with TimeZoneAwareExpression with NullIntolerant {

Review Comment:
   do we still need this parent class?



-- 
This is an automated message from the Apache Git Service.
To respond to the message, please log on to GitHub and use the
URL above to go to the specific comment.

To unsubscribe, e-mail: reviews-unsubscribe@spark.apache.org

For queries about this service, please contact Infrastructure at:
users@infra.apache.org


---------------------------------------------------------------------
To unsubscribe, e-mail: reviews-unsubscribe@spark.apache.org
For additional commands, e-mail: reviews-help@spark.apache.org