mysqldump slow with tables in big databases

On an environment with more thatn 500000 tables, the mysqldump is slow on dumping separate tables.

mysqldump uses the traditional queries like

show table status like 'a\_test\_bgtable\_2';

SHOW TRIGGERS LIKE ''a\_test\_bgtable\_2';

SHOW TABLES LIKE ''a\_test\_bgtable\_2';

instead of querying information_schema.tables .

select *

from information_schema.tables

where table_schema = 'test_tmp'

and table_name = 'a_test_bgtable_2';

takes 0.0011s, while

use test_tmp;

show tables like 'a\_test\_bgtable\_2';

takes about 10 seconds. This makes the dumps unnecessary slow.

mysqldump could use the information_schema here (after checking the server version), or the server could detect LIKE-Patterns that can only expand to exactly one table name (because there are no wildcards) and use a more intelligent algorithm internally, e.g. use the implementation of information_schema.tables .