Supported DML and DDL operations

If a new column is added to the source and the operation is successfully executed on the destination, the following limitations apply:

• If you add a column that has a DEFAULT VALUE, the new column in the destination table is created with a NULL value. When new data is added to this column in the source, the real-time sync task synchronizes the new data to the destination column.
• If you add a VIRTUAL column, the new column in the destination table is created with a NULL value. When new data is added to this column in the source, the real-time sync task synchronizes the new data to the destination column.

For real-time synchronization from MySQL and PolarDB for MySQL sources, add new columns to the end of the source table. Do not add columns between existing fields. If you must add a column between existing fields in the source table, the following constraints apply:

• In an initial full and incremental synchronization solution, do not add columns between existing fields during the full synchronization phase. Otherwise, data anomalies occur during the real-time synchronization phase.
• During the real-time synchronization phase, you must set the synchronization offset reset time to a point after the DDL event that added the column. Otherwise, subsequent real-time synchronization results in data anomalies.

If data anomalies occur, you can run the initial full data synchronization solution again to recover the data. To do this, remove the table to which the column was added and then re-initialize the data for that table. You do not need to re-initialize all tables in the task.

The following table describes the support for DML and DDL operations on the destination in real-time synchronization scenarios.