wuchong commented on a change in pull request #15755:
URL: https://github.com/apache/flink/pull/15755#discussion_r620947942



##########
File path: 
flink-table/flink-table-planner-blink/src/main/java/org/apache/flink/table/planner/utils/OperationConverterUtils.java
##########
@@ -144,6 +149,116 @@ public static Operation convertChangeColumn(
         // TODO: handle watermark and constraints
     }
 
+    public static Operation convertRenameColumn(
+            ObjectIdentifier tableIdentifier,
+            String originColumnName,
+            String newColumnName,
+            CatalogTable catalogTable) {
+
+        Schema modifiedTableSchema = catalogTable.getUnresolvedSchema();
+        validateColumnName(originColumnName, newColumnName, 
modifiedTableSchema);
+
+        Schema.Builder builder = Schema.newBuilder();
+        // build column
+        modifiedTableSchema.getColumns().stream()
+                .forEach(
+                        column -> {
+                            if (StringUtils.equals(column.getName(), 
originColumnName)) {
+                                buildNewColumnFromOriginColumn(builder, 
column, newColumnName);
+                            } else {
+                                buildNewColumnFromOriginColumn(builder, 
column, column.getName());
+                            }
+                        });
+        // build primary key column
+        List<String> originPrimaryKeyNames =
+                modifiedTableSchema
+                        .getPrimaryKey()
+                        .map(Schema.UnresolvedPrimaryKey::getColumnNames)
+                        .orElseGet(Lists::newArrayList);
+
+        List<String> newPrimaryKeyNames =
+                originPrimaryKeyNames.stream()
+                        .map(
+                                pkName ->
+                                        StringUtils.equals(pkName, 
originColumnName)
+                                                ? newColumnName
+                                                : pkName)
+                        .collect(Collectors.toList());
+
+        if (newPrimaryKeyNames.size() > 0) {
+            builder.primaryKey(newPrimaryKeyNames);
+        }
+        // build watermark
+        modifiedTableSchema.getWatermarkSpecs().stream()
+                .forEach(
+                        watermarkSpec -> {
+                            String watermarkRefColumnName = 
watermarkSpec.getColumnName();
+                            Expression watermarkExpression = 
watermarkSpec.getWatermarkExpression();
+                            if (StringUtils.equals(watermarkRefColumnName, 
originColumnName)) {
+                                String newWatermarkExpression =
+                                        ((SqlCallExpression) 
watermarkExpression)
+                                                .getSqlExpression()
+                                                
.replace(watermarkRefColumnName, newColumnName);

Review comment:
       Thanks @twalthr . I suggest resolve the schema first and traverse the 
node tree to check whether it contains the renamed column, and throw a helpful 
exception if contains. 




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