Re: [PR] [cdc]supported schemaEvolution when restarting the paimon cdc job [paimon]

["MOBIN-F (via GitHub)" <gi...@apache.org>]

MOBIN-F commented on code in PR #3362:
URL: https://github.com/apache/paimon/pull/3362#discussion_r1608023414


##########
paimon-flink/paimon-flink-cdc/src/main/java/org/apache/paimon/flink/action/cdc/postgres/PostgresRecordParser.java:
##########
@@ -209,6 +226,18 @@ private DataType extractFieldType(DebeziumEvent.Field field) {
             case "boolean":
                 return DataTypes.BOOLEAN();
             case "string":
+                int newLength = afterData.get(field.field()).asText().length();
+                if (paimonField == null) {
+                    return DataTypes.VARCHAR(newLength == 0 ? MIN_LENGTH : newLength);
+                } else if (paimonField.type() instanceof VarCharType) {
+                    int oldLength = ((VarCharType) paimonField.type()).getLength();
+                    return DataTypes.VARCHAR(
+                            Math.max(oldLength, newLength == 0 ? MIN_LENGTH : newLength));
+                } else if (paimonField.type() instanceof CharType) {
+                    int oldLength = ((CharType) paimonField.type()).getLength();
+                    return DataTypes.CHAR(
+                            Math.max(oldLength, newLength == 0 ? MIN_LENGTH : newLength));
+                }

Review Comment:
   in case "string", We cannot convert the varchar(n)/char(n) type into the string type, which will cause schemaCompatible to fail if the field changes when restarting the paimon-cdc job, because the string length of paimon is integer.max is always greater than n.
   At the same time, when pg table performs column type alter(example: n changes from 10 to 20), because pg-debezium does not have ddl event, we can only get the length value n from the record



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