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This topic has been translated from a Chinese forum by GPT and might contain errors.Original topic: ticdc事件合并问题
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username: meiliangdeng
In the same transaction, multiple update [or on duplicate key update] CDC events for the same piece of data will be merged.
If they are not in the same transaction, they will not be merged.
Here is an example:
CREATE TABLE `store_dml_test` (
`id` bigint(20) unsigned NOT NULL COMMENT 'id',
`store_id` bigint(20) unsigned NOT NULL COMMENT 'store id',
`create_time` datetime(3) NOT NULL DEFAULT CURRENT_TIMESTAMP(3) COMMENT 'creation time',
PRIMARY KEY (`id`) /*T![clustered_index] CLUSTERED */
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_bin
Suppose there is already a record with id=5653233197006196741 in the table:
If the following 3 update statements [3 transactions] are executed consecutively, ticdc will subscribe to 3 update events:
update store_dml_test set store_id = 50 where id = 5653233197006196741;
update store_dml_test set store_id = 51 where id = 5653233197006196741;
update store_dml_test set store_id = 52 where id = 5653233197006196741;
But if the following 3 update statements [in 1 transaction] are executed, ticdc will only subscribe to the last update event:
begin;
update store_mark_dml_test set store_id = 30 where id = 5653233197006196741;
update store_mark_dml_test set store_id = 31 where id = 5653233197006196741;
update store_mark_dml_test set store_id = 32 where id = 5653233197006196741;
commit;
Is there a configuration in TiDB that supports subscribing to 3 messages from ticdc regardless of the situation, instead of just 1?
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