1SET @start_global_value = @@global.innodb_random_read_ahead; 2SELECT @start_global_value; 3@start_global_value 40 5Valid values are 'ON' and 'OFF' 6select @@global.innodb_random_read_ahead in (0, 1); 7@@global.innodb_random_read_ahead in (0, 1) 81 9select @@global.innodb_random_read_ahead; 10@@global.innodb_random_read_ahead 110 12select @@session.innodb_random_read_ahead; 13ERROR HY000: Variable 'innodb_random_read_ahead' is a GLOBAL variable 14show global variables like 'innodb_random_read_ahead'; 15Variable_name Value 16innodb_random_read_ahead OFF 17show session variables like 'innodb_random_read_ahead'; 18Variable_name Value 19innodb_random_read_ahead OFF 20select * from information_schema.global_variables where variable_name='innodb_random_read_ahead'; 21VARIABLE_NAME VARIABLE_VALUE 22INNODB_RANDOM_READ_AHEAD OFF 23select * from information_schema.session_variables where variable_name='innodb_random_read_ahead'; 24VARIABLE_NAME VARIABLE_VALUE 25INNODB_RANDOM_READ_AHEAD OFF 26set global innodb_random_read_ahead='ON'; 27select @@global.innodb_random_read_ahead; 28@@global.innodb_random_read_ahead 291 30select * from information_schema.global_variables where variable_name='innodb_random_read_ahead'; 31VARIABLE_NAME VARIABLE_VALUE 32INNODB_RANDOM_READ_AHEAD ON 33select * from information_schema.session_variables where variable_name='innodb_random_read_ahead'; 34VARIABLE_NAME VARIABLE_VALUE 35INNODB_RANDOM_READ_AHEAD ON 36set @@global.innodb_random_read_ahead=0; 37select @@global.innodb_random_read_ahead; 38@@global.innodb_random_read_ahead 390 40select * from information_schema.global_variables where variable_name='innodb_random_read_ahead'; 41VARIABLE_NAME VARIABLE_VALUE 42INNODB_RANDOM_READ_AHEAD OFF 43select * from information_schema.session_variables where variable_name='innodb_random_read_ahead'; 44VARIABLE_NAME VARIABLE_VALUE 45INNODB_RANDOM_READ_AHEAD OFF 46set global innodb_random_read_ahead=1; 47select @@global.innodb_random_read_ahead; 48@@global.innodb_random_read_ahead 491 50select * from information_schema.global_variables where variable_name='innodb_random_read_ahead'; 51VARIABLE_NAME VARIABLE_VALUE 52INNODB_RANDOM_READ_AHEAD ON 53select * from information_schema.session_variables where variable_name='innodb_random_read_ahead'; 54VARIABLE_NAME VARIABLE_VALUE 55INNODB_RANDOM_READ_AHEAD ON 56set @@global.innodb_random_read_ahead='OFF'; 57select @@global.innodb_random_read_ahead; 58@@global.innodb_random_read_ahead 590 60select * from information_schema.global_variables where variable_name='innodb_random_read_ahead'; 61VARIABLE_NAME VARIABLE_VALUE 62INNODB_RANDOM_READ_AHEAD OFF 63select * from information_schema.session_variables where variable_name='innodb_random_read_ahead'; 64VARIABLE_NAME VARIABLE_VALUE 65INNODB_RANDOM_READ_AHEAD OFF 66set session innodb_random_read_ahead='OFF'; 67ERROR HY000: Variable 'innodb_random_read_ahead' is a GLOBAL variable and should be set with SET GLOBAL 68set @@session.innodb_random_read_ahead='ON'; 69ERROR HY000: Variable 'innodb_random_read_ahead' is a GLOBAL variable and should be set with SET GLOBAL 70set global innodb_random_read_ahead=1.1; 71ERROR 42000: Incorrect argument type to variable 'innodb_random_read_ahead' 72set global innodb_random_read_ahead=1e1; 73ERROR 42000: Incorrect argument type to variable 'innodb_random_read_ahead' 74set global innodb_random_read_ahead=2; 75ERROR 42000: Variable 'innodb_random_read_ahead' can't be set to the value of '2' 76set global innodb_random_read_ahead=-3; 77ERROR 42000: Variable 'innodb_random_read_ahead' can't be set to the value of '-3' 78select @@global.innodb_random_read_ahead; 79@@global.innodb_random_read_ahead 800 81select * from information_schema.global_variables where variable_name='innodb_random_read_ahead'; 82VARIABLE_NAME VARIABLE_VALUE 83INNODB_RANDOM_READ_AHEAD OFF 84select * from information_schema.session_variables where variable_name='innodb_random_read_ahead'; 85VARIABLE_NAME VARIABLE_VALUE 86INNODB_RANDOM_READ_AHEAD OFF 87set global innodb_random_read_ahead='AUTO'; 88ERROR 42000: Variable 'innodb_random_read_ahead' can't be set to the value of 'AUTO' 89SET @@global.innodb_random_read_ahead = @start_global_value; 90SELECT @@global.innodb_random_read_ahead; 91@@global.innodb_random_read_ahead 920 93