Hi, Lixun!

On Jun 18, Lixun Peng wrote:
> Hi,
>
> As we know, InnoDB has implicit primary key if a table hasn't defined
> a primary key.  However MySQL server doesn't know this primary key, so
> this primary key will not apear in binlog.
>
> When we are using ROW format binlog for replication, if a table has no any
> indexes, that's a disaster. If a table without indexes do a DML
> (UPDATE/DELETE), of course it will run a long time in master, but in slave,
> it still need a long time. It will cause serious slave replication delay.

...

> I think mysql server can do the same thing as InnoDB do, if user doesn't
> define the primary key, mysql can add the primary key automatically.
>

> How do you think?

Well, that's doable. A much easier solution would be to require a user
to create a primary key. It's a one-line change:

-  Table_flags ha_table_flags() const { return cached_table_flags; }
+  Table_flags ha_table_flags() const { return cached_table_flags | HA_REQUIRE_PRIMARY_KEY; }

But what you suggest is possible too, I believe.

Regards,
Sergei