RaigorJiang commented on issue #22058:
URL:
https://github.com/apache/shardingsphere/issues/22058#issuecomment-1310145360
Hi @peilinqian
Thanks for your feedback, and I have reproduced the problem from master
branch.
We get this error message because a single table already exists in the
resource registered, and after creating the `READWRITE_SPLITTING RULE`, the
single table will use the aggregate data source `readwrite_ds`.
Therefore, if there is no table in the registered resource, this
`readwrite_ds` can be dropped.
### The latest reproduction process:
```sql
REGISTER STORAGE UNIT write_ds (
HOST="127.0.0.1",
PORT=3306,
DB="demo_write_ds",
USER="root",
PASSWORD="123456"
), read_ds (
HOST="127.0.0.1",
PORT=3306,
DB="demo_read_ds",
USER="root",
PASSWORD="123456"
);
SET DEFAULT SINGLE TABLE STORAGE UNIT = write_ds;
CREATE TABLE `t_order` (
`order_id` bigint(20) NOT NULL AUTO_INCREMENT,
`user_id` int(11) NOT NULL,
`status` varchar(50) DEFAULT NULL,
PRIMARY KEY (`order_id`)
);
CREATE READWRITE_SPLITTING RULE group_0 (
WRITE_STORAGE_UNIT=write_ds,
READ_STORAGE_UNITS(read_ds),
TYPE(NAME="random")
);
DROP READWRITE_SPLITTING RULE group_0;
````
Error: Readwrite splitting rules `[group_0]` in database `xxx` are still in
used.
### Analyze
I would say that this restriction is actually correct. Consider a scenario:
When `write_ds` and `read_ds` are a set of primary-replica cluster, when
there is already a table, dropping the rule may cause `INSERT SQL` to be routed
to `read_ds`, which will cause serious errors.
Therefore, if there is already a single table in the logic database that
uses `readwrite_ds`, dropping rule is not allowed.
So, what are the scenarios where you need to drop the rules when using the
primary-replica cluster?
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