1SET @start_global_value = @@global.optimizer_trace; 2SELECT @start_global_value; 3@start_global_value 4enabled=off,one_line=off 5select @@global.optimizer_trace; 6@@global.optimizer_trace 7enabled=off,one_line=off 8select @@session.optimizer_trace; 9@@session.optimizer_trace 10enabled=off,one_line=off 11show global variables like 'optimizer_trace'; 12Variable_name Value 13optimizer_trace enabled=off,one_line=off 14show session variables like 'optimizer_trace'; 15Variable_name Value 16optimizer_trace enabled=off,one_line=off 17select * from information_schema.global_variables where variable_name='optimizer_trace'; 18VARIABLE_NAME VARIABLE_VALUE 19OPTIMIZER_TRACE enabled=off,one_line=off 20select * from information_schema.session_variables where variable_name='optimizer_trace'; 21VARIABLE_NAME VARIABLE_VALUE 22OPTIMIZER_TRACE enabled=off,one_line=off 23set global optimizer_trace=1; 24select @@global.optimizer_trace; 25@@global.optimizer_trace 26enabled=on,one_line=off 27set session optimizer_trace=1; 28select @@session.optimizer_trace; 29@@session.optimizer_trace 30enabled=on,one_line=off 31set global optimizer_trace=0; 32select @@global.optimizer_trace; 33@@global.optimizer_trace 34enabled=off,one_line=off 35set session optimizer_trace=0; 36select @@session.optimizer_trace; 37@@session.optimizer_trace 38enabled=off,one_line=off 39set session optimizer_trace=default; 40select @@session.optimizer_trace; 41@@session.optimizer_trace 42enabled=off,one_line=off 43set global optimizer_trace=1.1; 44ERROR 42000: Incorrect argument type to variable 'optimizer_trace' 45set global optimizer_trace=1e1; 46ERROR 42000: Incorrect argument type to variable 'optimizer_trace' 47set session optimizer_trace="foobar"; 48ERROR 42000: Variable 'optimizer_trace' can't be set to the value of 'foobar' 49SET @@global.optimizer_trace = @start_global_value; 50SELECT @@global.optimizer_trace; 51@@global.optimizer_trace 52enabled=off,one_line=off 53