MySQL优化之SQL耗时瓶颈 SHOW profiles

1、首先查看是否开启profiling功能

SHOW VARIABLES LIKE '%pro%';

或者

SELECT @@profiling;

2、开启profiling

SET profiling=1;

3、执行sql语句

例如：

SELECT
  table_schema AS 'Db Name',
  ROUND( SUM( data_length + index_length ) / 1024 / 1024, 3 ) AS 'Db Size (MB)',
  ROUND( SUM( data_free ) / 1024 / 1024, 3 ) AS 'Free Space (MB)'
FROM information_schema.tables
GROUP BY table_schema ;

4、查看结果

SHOW profiles;

SHOW profile ALL FOR QUERY 94;

94是查询ID号。

SHOW profiles语法：

SHOW PROFILE [type [, type] … ]
    [FOR QUERY n]
    [LIMIT row_count [OFFSET offset]]


type:
    ALL
  | BLOCK IO
  | CONTEXT SWITCHES
  | CPU
  | IPC
  | MEMORY
  | PAGE FAULTS
  | SOURCE
  | SWAPS