maria-developers team mailing list archive

[Sergei Golubchik <serg@xxxxxxxxxxxx>]

Hi, MARK!

On Nov 29, MARK CALLAGHAN wrote:
> Is there an easy way to prevent SET GLOBAL ... from being done for
> plugin variables declared via MYSQL_THDVAR_...? For the following
> variable I can do SET GLOBAL innodb_fake_changes=1 and that sets a
> global variable.
> 
> static MYSQL_THDVAR_BOOL(fake_changes, PLUGIN_VAR_OPCMDARG,
>   "In the transaction after enabled, UPDATE, INSERT and DELETE only
> move the cursor to the records "
>   "and do nothing other operations (no changes, no ibuf, no undo, no
> transaction log) in the transaction. "
>   "This is to cause replication prefetch IO. ATTENTION: the
> transaction started after enabled is affected.",
>   check_fake_changes, NULL, FALSE);

I couldn't find a proper solution, but here's a workaround. Provide an
update function for your variable:

-   check_fake_changes, NULL, FALSE);
+   check_fake_changes, update_fake_changes, FALSE);
+
+ void update_fake_changes(MYSQL_THD thd, struct st_mysql_sys_var *var,
+                          void *var_ptr, const void *save)
+ {
+   if (var_ptr != THDVAR(0, fake_changes))
+     *(my_bool *) var_ptr= *(my_bool *) save ? TRUE : FALSE;
+ }

it isn't very cool, because one is supposed to do all the checks in the
check function, not in the update. but it'll work.

Regards,
Sergei