maria-developers team mailing list archive

[Alexey Botchkov <holyfoot@xxxxxxxxxxxx>]

Hi, Sergei.

> Could you, please remove that piece of fine creativity and
> thd->clear_error() too and use the error handler instead?

There's one puzzle.
We need to fill the INFORMATION_SCHEMA.TABLES.TABLE_COMMENT field.
If a table exists but corrupt, that field presently is filled with the 
error message.
Like here (tx.MYD and tx.MYI files were removed, only tx.frm left):
mysql> SELECT TABLE_SCHEMA, TABLE_NAME, TABLE_TYPE, ENGINE, ROW_FORMAT, 
TABLE_ROWS, DATA_LENGTH, TABLE_CO MMENT FROM INFORMATION_SCHEMA.TABLES 
WHERE TABLE_NAME = 'tx';
+--------------+------------+------------+--------+------------+------------+-------------+-------------- 
--------------------+
| TABLE_SCHEMA | TABLE_NAME | TABLE_TYPE | ENGINE | ROW_FORMAT | 
TABLE_ROWS | DATA_LENGTH | 
TABLE_COMMENT                                          |
+--------------+------------+------------+--------+------------+------------+-------------+-------------- 
--------------------+
| test         | tx         | BASE TABLE | NULL   | NULL |       NULL 
|        NULL | Can't find file: 'tx' (errno: 2) |
+--------------+------------+------------+--------+------------+------------+-------------+----------------------------------+
1 row in set, 5 warnings (0.00 sec)

This field is set here:
sql_show.cc:4899 (get_schema_tables_record())
  if (res || info_error)
  {
    /*
      If an error was encountered, push a warning, set the TABLE COMMENT
      column with the error text, and clear the error so that the operation
      can continue.
    */
    const char *error= thd->is_error() ? thd->stmt_da->message() : "";
    table->field[20]->store(error, strlen(error), cs);

    if (thd->is_error())
    {
      push_warning(thd, MYSQL_ERROR::WARN_LEVEL_WARN,
                   thd->stmt_da->sql_errno(), thd->stmt_da->message());
      thd->clear_error();
    }
  }

As we're supposed to block that error with the Error_handler, the error 
message gets lost there
and cannot be recovered later in the get_schema_tables_record.
So we either have stop showing the error message in that field, or we 
have to store it somewhere.
The Error_handler looks like a good place to store that error message. 
But i can't figure out how to
send it to the get_schema_tables_record() nicely.
Another place is the TABLE_LIST * parameter. Seems to be convenient for 
eveything.
Though the TABLE_LIST structure will get even more polluted.

Sergei, what is your opinion here?

Best regards.
HF




17.02.2014 20:30, Sergei Golubchik wrote:
Hi, Alexey! On Feb 14, Alexey Botchkov wrote:
> > > But I don't understand that. Do you mean, old code did *not* suppress
> > > errors here? How could selects from I_S tables work without it?
> > Here's how it works today:
> >
> > get_all_tables()
> >    Trigger_error_handler err_handler;
> >    thd->push_internal_handler(&err_handler);
> >    fill_schema_table_from_frm
> >      get_table_share
> >        .... /* here we get the error of file not found */
> >          my_message_sql
> >            THD::raise_condition
> >              /* here we test the err_handler */
> >              /* but it doesn't react on that kind of errors */
> >              mysql_audit_notify()
> >              stmt_da->set_error_status
> >              warning_info->push_warning
> >            /
> >          /
> >        .... /*error is returned back along the call stack */
> >      /
> >      thd->clear_error(); /*which erases all the fileopen errors*/
> >    /
> >
> > So basically the error is launched and then erased. Which doesn't help
> > with the plugin notifications.
> > To fix that i added one more error handler.
> It's worse than that :)
> After thd->clear_error() the error flag is cleared, indeed. But all
> issued errors are still present in the warning list. I've looked into
> this about found this little gem: do_fill_table() function.
>
> It actually copies Warning_info list and removes warnings from there!
>
> Could you, please remove that piece of fine creativity and
> thd->clear_error() too and use the error handler instead?
>
> Looking at the logic of do_fill_table(), all you need to do is to
> filter out all errors, but keep all warnings. Like
>
>    class Warnings_only_error_handler : public Internal_error_handler
>    {
>    public:
>      bool handle_condition(THD *thd, uint sql_errno, const char* sqlstate,
>                            MYSQL_ERROR::enum_warning_level level,
>                            const char* msg, MYSQL_ERROR ** cond_hdl)
>      {
>        return level == MYSQL_ERROR::WARN_LEVEL_ERROR;
>      }
>    };
>
>
> Regards,
> Sergei