1SET @start_global_value = @@global.innodb_read_ahead_threshold; 2SELECT @start_global_value; 3@start_global_value 456 5Valid values are between 0 and 64 6select @@global.innodb_read_ahead_threshold between 0 and 64; 7@@global.innodb_read_ahead_threshold between 0 and 64 81 9select @@global.innodb_read_ahead_threshold; 10@@global.innodb_read_ahead_threshold 1156 12select @@session.innodb_read_ahead_threshold; 13ERROR HY000: Variable 'innodb_read_ahead_threshold' is a GLOBAL variable 14show global variables like 'innodb_read_ahead_threshold'; 15Variable_name Value 16innodb_read_ahead_threshold 56 17show session variables like 'innodb_read_ahead_threshold'; 18Variable_name Value 19innodb_read_ahead_threshold 56 20select * from information_schema.global_variables where variable_name='innodb_read_ahead_threshold'; 21VARIABLE_NAME VARIABLE_VALUE 22INNODB_READ_AHEAD_THRESHOLD 56 23select * from information_schema.session_variables where variable_name='innodb_read_ahead_threshold'; 24VARIABLE_NAME VARIABLE_VALUE 25INNODB_READ_AHEAD_THRESHOLD 56 26set global innodb_read_ahead_threshold=10; 27select @@global.innodb_read_ahead_threshold; 28@@global.innodb_read_ahead_threshold 2910 30select * from information_schema.global_variables where variable_name='innodb_read_ahead_threshold'; 31VARIABLE_NAME VARIABLE_VALUE 32INNODB_READ_AHEAD_THRESHOLD 10 33select * from information_schema.session_variables where variable_name='innodb_read_ahead_threshold'; 34VARIABLE_NAME VARIABLE_VALUE 35INNODB_READ_AHEAD_THRESHOLD 10 36set session innodb_read_ahead_threshold=1; 37ERROR HY000: Variable 'innodb_read_ahead_threshold' is a GLOBAL variable and should be set with SET GLOBAL 38set global innodb_read_ahead_threshold=DEFAULT; 39select @@global.innodb_read_ahead_threshold; 40@@global.innodb_read_ahead_threshold 4156 42set global innodb_read_ahead_threshold=1.1; 43ERROR 42000: Incorrect argument type to variable 'innodb_read_ahead_threshold' 44set global innodb_read_ahead_threshold=1e1; 45ERROR 42000: Incorrect argument type to variable 'innodb_read_ahead_threshold' 46set global innodb_read_ahead_threshold="foo"; 47ERROR 42000: Incorrect argument type to variable 'innodb_read_ahead_threshold' 48set global innodb_read_ahead_threshold=' '; 49ERROR 42000: Incorrect argument type to variable 'innodb_read_ahead_threshold' 50select @@global.innodb_read_ahead_threshold; 51@@global.innodb_read_ahead_threshold 5256 53set global innodb_read_ahead_threshold=" "; 54ERROR 42000: Incorrect argument type to variable 'innodb_read_ahead_threshold' 55select @@global.innodb_read_ahead_threshold; 56@@global.innodb_read_ahead_threshold 5756 58set global innodb_read_ahead_threshold=-7; 59Warnings: 60Warning 1292 Truncated incorrect innodb_read_ahead_threshold value: '-7' 61select @@global.innodb_read_ahead_threshold; 62@@global.innodb_read_ahead_threshold 630 64select * from information_schema.global_variables where variable_name='innodb_read_ahead_threshold'; 65VARIABLE_NAME VARIABLE_VALUE 66INNODB_READ_AHEAD_THRESHOLD 0 67set global innodb_read_ahead_threshold=96; 68Warnings: 69Warning 1292 Truncated incorrect innodb_read_ahead_threshold value: '96' 70select @@global.innodb_read_ahead_threshold; 71@@global.innodb_read_ahead_threshold 7264 73select * from information_schema.global_variables where variable_name='innodb_read_ahead_threshold'; 74VARIABLE_NAME VARIABLE_VALUE 75INNODB_READ_AHEAD_THRESHOLD 64 76set global innodb_read_ahead_threshold=0; 77select @@global.innodb_read_ahead_threshold; 78@@global.innodb_read_ahead_threshold 790 80set global innodb_read_ahead_threshold=64; 81select @@global.innodb_read_ahead_threshold; 82@@global.innodb_read_ahead_threshold 8364 84SET @@global.innodb_read_ahead_threshold = @start_global_value; 85SELECT @@global.innodb_read_ahead_threshold; 86@@global.innodb_read_ahead_threshold 8756 88