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Re: Rev 4029: MDEV-4856 SQL_ERROR_LOG shows 1146 errors which didnt appear in mysql client


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.
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());

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.

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:

   Trigger_error_handler err_handler;
       .... /* here we get the error of file not found */
             /* here we test the err_handler */
             /* but it doesn't react on that kind of errors */
       .... /*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
     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;


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