dawidwys commented on code in PR #23633:
URL: https://github.com/apache/flink/pull/23633#discussion_r1380400786


##########
flink-table/flink-table-planner/src/main/scala/org/apache/flink/table/planner/typeutils/TypeCoercion.scala:
##########
@@ -53,85 +53,4 @@ object TypeCoercion {
 
       case _ => false
     }
-
-  /**
-   * All the supported cast types in flink-table.
-   *
-   * Note: No distinction between explicit and implicit conversions Note: This 
is a subset of
-   * SqlTypeAssignmentRule Note: This may lose type during the cast.
-   */
-  def canCast(from: LogicalType, to: LogicalType): Boolean =
-    (from.getTypeRoot, to.getTypeRoot) match {
-      case (_, _) if from == to => true
-
-      case (_, VARCHAR | CHAR) => true
-
-      case (VARCHAR | CHAR, _) if isNumeric(to) => true
-      case (VARCHAR | CHAR, BOOLEAN) => true
-      case (VARCHAR | CHAR, DECIMAL) => true
-      case (VARCHAR | CHAR, DATE) => true
-      case (VARCHAR | CHAR, TIME_WITHOUT_TIME_ZONE) => true
-      case (VARCHAR | CHAR, TIMESTAMP_WITHOUT_TIME_ZONE) => true
-      case (VARCHAR | CHAR, TIMESTAMP_WITH_LOCAL_TIME_ZONE) => true
-
-      case (BOOLEAN, _) if isNumeric(to) => true
-      case (BOOLEAN, DECIMAL) => true
-      case (_, BOOLEAN) if isNumeric(from) => true
-      case (DECIMAL, BOOLEAN) => true
-
-      case (_, _) if isNumeric(from) && isNumeric(to) => true
-      case (_, DECIMAL) if isNumeric(from) => true
-      case (DECIMAL, _) if isNumeric(to) => true
-      case (DECIMAL, DECIMAL) => true
-      case (INTEGER, DATE) => true
-      case (INTEGER, TIME_WITHOUT_TIME_ZONE) => true
-      case (TINYINT, TIMESTAMP_WITHOUT_TIME_ZONE) => true
-      case (SMALLINT, TIMESTAMP_WITHOUT_TIME_ZONE) => true
-      case (INTEGER, TIMESTAMP_WITHOUT_TIME_ZONE) => true
-      case (BIGINT, TIMESTAMP_WITHOUT_TIME_ZONE) => true
-      case (DOUBLE, TIMESTAMP_WITHOUT_TIME_ZONE) => true
-      case (FLOAT, TIMESTAMP_WITHOUT_TIME_ZONE) => true
-      case (INTEGER, INTERVAL_YEAR_MONTH) => true
-      case (BIGINT, INTERVAL_DAY_TIME) => true
-
-      case (DATE, TIME_WITHOUT_TIME_ZONE) => false
-      case (TIME_WITHOUT_TIME_ZONE, DATE) => false
-      case (_, _) if isTimePoint(from) && isTimePoint(to) => true
-      case (DATE, INTEGER) => true
-      case (TIME_WITHOUT_TIME_ZONE, INTEGER) => true
-      case (TIMESTAMP_WITHOUT_TIME_ZONE, TINYINT) => true
-      case (TIMESTAMP_WITHOUT_TIME_ZONE, INTEGER) => true
-      case (TIMESTAMP_WITHOUT_TIME_ZONE, SMALLINT) => true
-      case (TIMESTAMP_WITHOUT_TIME_ZONE, BIGINT) => true
-      case (TIMESTAMP_WITHOUT_TIME_ZONE, DOUBLE) => true
-      case (TIMESTAMP_WITHOUT_TIME_ZONE, FLOAT) => true
-
-      case (INTERVAL_YEAR_MONTH, INTEGER) => true
-      case (INTERVAL_DAY_TIME, BIGINT) => true
-
-      case _ => false
-    }
-
-  /** All the supported reinterpret types in flink-table. */
-  def canReinterpret(from: LogicalType, to: LogicalType): Boolean =
-    (from.getTypeRoot, to.getTypeRoot) match {
-      case (_, _) if from == to => true
-
-      case (DATE, INTEGER) => true
-      case (TIME_WITHOUT_TIME_ZONE, INTEGER) => true
-      case (TIMESTAMP_WITHOUT_TIME_ZONE, BIGINT) => true
-      case (INTEGER, DATE) => true
-      case (INTEGER, TIME_WITHOUT_TIME_ZONE) => true
-      case (BIGINT, TIMESTAMP_WITHOUT_TIME_ZONE) => true
-      case (INTEGER, INTERVAL_YEAR_MONTH) => true
-      case (BIGINT, INTERVAL_DAY_TIME) => true
-      case (INTERVAL_YEAR_MONTH, INTEGER) => true
-      case (INTERVAL_DAY_TIME, BIGINT) => true
-
-      case (DATE, BIGINT) => true
-      case (TIME_WITHOUT_TIME_ZONE, BIGINT) => true
-      case (INTERVAL_YEAR_MONTH, BIGINT) => true
-
-      case _ => false

Review Comment:
   `canCast` method I removed because it was not used
   
   Now, answering you question. The way I understand it. `REINTERPRET_CAST` is 
an internal function, that requires knowledge of the internal data formats. It 
says to change the logical type without touching the underlying data format. It 
can be used if both logical types use the same physical format.
   
   `CAST` can actually modify data. E.g. you can cast an INT to STRING which 
changes the underlying format etc.
   



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