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