Controlling Switchable Optimization in mysql
Controlling Switchable Optimization in mysql ,
The optimizer_switch system variable enables control over optimizer behavior. Its value is a set of flags, each of which has a value of on or off to indicate whether the corresponding optimizer behavior is enabled or disabled. This variable has global and session values and can be changed at runtime. The global default can be set at server startup.
To change the value of optimizer_switch, assign a value consisting of a comma-separated list of one or more commands:
SET [GLOBAL|SESSION] optimizer_switch='command[,command]...';
Each command value should have one of the forms shown in the following table.
default - Reset every optimization to its default value
opt_name=default - Set the named optimization to its default value
opt_name=off - Disable the named optimization
opt_name=on - Enable the named optimization