innodb_expand_undo_slots

This patch provide the new startup option to expand maximum number of undo slots. In normal version, the value is fixed to 1024.

It is not recommended to use this option, unless you have troubles with the warning “Warning: cannot find a free slot for an undo log”.

• innodb_extra_undoslots (default false) - if set true, the maximum number of undo slots expanded to 4072

ATTENTION: If the option was enabled and the expanded slots are used, you cannot use the datafile for the all programs which assume 1024 slots (e.g. the other mysqld or ibbackup).

You can check whether the expanded slots (1025-4072) are used or not by startup with innodb_expand_undoslots=false.

• used: mysqld doesn't start with “Error:” in error log

"InnoDB: Error: innodb_extra_undoslots option is disabled, but it was enabled before.\n"
"InnoDB: The datafile is not normal for mysqld and disabled innodb_extra_undoslots.\n"
"InnoDB: Enable innodb_extra_undoslots if it was enabled before, and\n"
"InnoDB: ### don't use this datafile with other mysqld or ibbackup! ###\n"
"InnoDB: Cannot continue operation for the safety. Calling exit(1).\n");

• not used: mysqld startswith “Warning:” in error log

"InnoDB: Warning: innodb_extra_undoslots option is disabled, but it was  enabled before.\n"
"InnoDB: But extended undo slots seem not used, so continue operation.\n");