OceanBase Schema Change Sync

OceanBase Schema Change Sync automatically applies upstream column changes to Doris target tables during continuous load. This capability applies only to OceanBase CDC with Auto Table Creation.

Experimental feature

OceanBase Schema Change Sync is available as an experimental feature starting from Doris 4.1.4 and supports only MySQL compatibility mode.

OceanBase uses the MySQL CDC schema change processing path, so its supported changes and behavior are the same as for MySQL.

Supported Schema Changes

OceanBase operation	Doris behavior
ADD COLUMN	Adds a column with the same name and a type defined by OceanBase Data Type Mapping, and copies the column comment. DEFAULT and NOT NULL constraints are not copied, and historical rows are not backfilled. Subsequent rows use the actual values written by OceanBase to the binlog.
DROP COLUMN	Drops the column with the same name.

Considerations

• If an added column already exists or a dropped column does not exist, Doris skips the operation so that retries do not fail the job.
• Column positions specified by FIRST and AFTER are not synchronized to Doris. New columns are appended after existing Doris columns.
• CHANGE COLUMN, MODIFY COLUMN, RENAME COLUMN, DEFAULT changes, and NULL / NOT NULL constraint changes are not synchronized automatically.
• Primary key, index, partition, table name, and other table-level schema changes are not synchronized automatically.
• Before an unsupported schema change, pause the continuous load job, change the Doris target table manually, verify that both schemas are compatible, and then resume the job.
• Auto Table Creation Sync enables Schema Change Sync by default. Doris currently does not provide a SQL property to disable it.

Example

Add a column to an OceanBase source table:

ALTER TABLE source_db.users ADD COLUMN city VARCHAR(50);
INSERT INTO source_db.users VALUES (2, 'Alice', 'Hangzhou');

After the job processes the incremental data, the city column appears in the Doris target table:

DESC target_db.users;

+-------+--------------+------+-------+---------+-------+
| Field | Type         | Null | Key   | Default | Extra |
+-------+--------------+------+-------+---------+-------+
| id    | int          | No   | true  | NULL    |       |
| name  | varchar(100) | Yes  | false | NULL    | NONE  |
| city  | varchar(50)  | Yes  | false | NULL    | NONE  |
+-------+--------------+------+-------+---------+-------+

Related Documents

• OceanBase CDC with Auto Table Creation
• OceanBase Data Type Mapping
• Continuous Load Overview