…that the enforcement of foreign keys incurs a significant performance overhead.1,2 MySQL allows us to set FOREIGN_KEY_CHECKS=…relationship: mysql> SELECT CONCAT( ‘SELECT ‘, GROUP_CONCAT(DISTINCT CONCAT(K.CONSTRAINT_NAME, ‘.’, P.COLUMN_NAME, ‘ AS `’, P.TABLE_SCHEMA, ‘.’, P.TABLE_NAME, ‘.’, P.COLUMN_…

… useful, simply ignore this column. It is used to prevent wide innodb primary keys on the MV. mysql> select mview$pk as rank… than COUNT(*). mysql> select count(*) cnt from order_lines\G *************************** 1. row *************************** cnt: 155187034 1 row in set (32.03 sec) mysql> select sum(total….03 sec) Notice the difference in response time. Refresh method performance comparison For demonstration purposes, I did the following: Created one…

…you perform match of constant which is too large to the column instead of simply responding with empty set MySQL truncates the constant, performs… for unsigned column and I would expect “Impossible Where clause” here Lets look at query execution: | Handler_read_next | 1305742982 | mysql> select count…

… indexing to be on that column. That would clearly save indexing space. Is this a reasonable performance optimization. (Keep in mind that… SELECT * FROM TBL WHERE hash=crc32(‘string’) AND string=’string’ The other thing you need to consider is string comparison in MySQL… worry about performance impact of extending index is when you increase its length dramatically, for example adding long varchar column. In such…