Changefeed DDL Replication

This document describes the rules and special cases of DDL replication in TiCDC.

DDL allow list

Currently, TiCDC uses an allow list to determine whether to replicate a DDL statement. Only the DDL statements in the allow list are replicated to the downstream. The DDL statements not in the allow list are not replicated.

The allow list of DDL statements supported by TiCDC is as follows:

create database
drop database
create table
drop table
add column
drop column
create index / add index
drop index
truncate table
modify column
rename table
alter column default value
alter table comment
rename index
add partition
drop partition
truncate partition
create view
drop view
alter table character set
alter database character set
recover table
add primary key
drop primary key
rebase auto id
alter table index visibility
exchange partition
reorganize partition
alter table ttl
alter table remove ttl

DDL replication considerations

Due to the lack of some context during the replication process, TiCDC has some constraints on the replication of RENAME TABLE DDLs.

Rename a single table in a DDL statement

If a DDL statement renames a single table, TiCDC only replicates the DDL statement when the old table name matches the filter rule. The following is an example.

Assume that the configuration file of your changefeed is as follows:

[filter]
rules = ['test.t*']

TiCDC processes this type of DDL as follows:

DDL	Whether to replicate	Reason for the handling
`RENAME TABLE test.t1 TO test.t2`	Replicate	`test.t1` matches the filter rule
`RENAME TABLE test.t1 TO ignore.t1`	Replicate	`test.t1` matches the filter rule
`RENAME TABLE ignore.t1 TO ignore.t2`	Ignore	`ignore.t1` does not match the filter rule
`RENAME TABLE test.n1 TO test.t1`	Report an error and exit the replication	`test.n1` does not match the filter rule, but `test.t1` matches the filter rule. This operation is illegal. In this case, refer to the error message for handling.
`RENAME TABLE ignore.t1 TO test.t1`	Report an error and exit the replication	Same reason as above.

Rename multiple tables in a DDL statement

If a DDL statement renames multiple tables, TiCDC only replicates the DDL statement when the old database name, old table names, and the new database name all match the filter rule.

In addition, TiCDC does not support the RENAME TABLE DDL that swaps the table names. The following is an example.