MySQL性能分析工具profiling
MySQL數據庫中，可以通過配置profiling參數來啓用SQL性能分析，找出當前SQL瓶頸，進而優化、調整sql語句。
profiling參數開啓後，後續執行的SQL語句都將記錄其資源開銷，諸如IO，IPC，CPU，Memory等等。
用法：
mysql> help profile
Name:'SHOW PROFILE'
Description:
Syntax:
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
Profiling變量默認值爲0（off），可以通過設置profiling爲0或ON開啓
mysql>select @@profiling;
+-------------+
|@@profiling |
+-------------+
| 0 |
+-------------+
1 row inset (0.03 sec)
mysql>show variables like '%profil%';
+------------------------+-------+
|Variable_name | Value |
+------------------------+-------+
|profiling | OFF |
|profiling_history_size | 15 |
+------------------------+-------+
2 rows inset (0.00 sec)
profiling：設置是否開啓SQL性能剖析
profiling_history_size：設置是SQL性能剖析緩存的記錄數
mysql>set profiling=1;
Query OK,0 rows affected (0.03 sec)
mysql>show variables like '%profil%';
+------------------------+-------+
|Variable_name | Value |
+------------------------+-------+
|profiling | ON |
|profiling_history_size | 15 |
+------------------------+-------+
2 rows inset (0.00 sec)
mysql>show variables like 'profiling_history_size';
+------------------------+-------+
|Variable_name | Value |
+------------------------+-------+
|profiling_history_size | 15 |
+------------------------+-------+
1 row inset (0.00 sec)
show profiles:返回一個列表,顯示最近發送到服務器上執行的語句的資源使用情況.
顯示的記錄數由變量“profiling_history_size”控制,默認15條，最大值爲100，可以手動設置該參數值。
mysql>set profiling_history_size = 30;
Query OK,0 rows affected (0.00 sec)
mysql>show variables like '%profil%';
+------------------------+-------+
|Variable_name | Value |
+------------------------+-------+
|profiling | ON |
|profiling_history_size | 30 |
+------------------------+-------+
2 rows inset (0.00 sec)
選項註釋：
type:
ALL ：顯示所有信息
|BLOCK IO ：塊設備IO輸入輸出次數
|CONTEXT SWITCHES：上下文切換相關開銷
|CPU：用戶和系統的CPU使用情況
|IPC：顯示發送和接收消息的相關消耗
|MEMORY：內存消耗情況（該版本is not currently implemented）
|PAGE FAULTS：顯示主要和次要頁面故障相關的開銷
|SOURCE：顯示和Source_function,Source_file,Source_line相關的開銷信息
|SWAPS：顯示交換次數相關的開銷
Profilingis enabled per session. When a session ends, itsprofiling
information is lost.
注意：profiling被應用在每一個會話中，當前會話關閉後，profiling統計的信息將丟失。
用法示例：
mysql>use mydb
mysql>drop table if exists t4;
Query OK,0 rows affected, 1 warning (0.00 sec)
mysql>create table cid(id int);
Query OK,0 rows affected (0.05 sec)
mysql>show profiles;
+----------+------------+----------------------------------------------+
| Query_ID| Duration |Query |
+----------+------------+----------------------------------------------+
| 1 | 0.00061900 | show variables like '%profil%' |
| 2 | 0.00061800 | show variables like 'profiling_history_size'|
| 3 | 0.00010600 | set profiling_history_size = 30 |
| 4 | 0.00078200 | show variables like '%profil%' |
| 5 | 0.00018800 | SELECT DATABASE() |
| 6 | 0.00050400 | show databases |
| 7 | 0.00032200 | show tables |
| 8 | 0.00027300 | drop table if exists t4 |
| 9 | 0.04367500 | create table cid(id int) |
+----------+------------+----------------------------------------------+
9 rows inset (0.00 sec)
mysql>show profile; -->默認會打開上一個語句的開銷信息
+----------------------+----------+
|Status | Duration |
+----------------------+----------+
|starting | 0.000074 |
| checkingpermissions | 0.000083 |
| creatingtable | 0.043427 |
| Aftercreate | 0.000014 |
| queryend | 0.000003 |
| freeingitems | 0.000068 |
| loggingslow query |0.000004 |
| cleaningup | 0.000002 |
+----------------------+----------+
8 rows inset (0.02 sec)
mysql>show profile for query 9; -->獲取指定查詢的開銷
+----------------------+----------+
|Status | Duration |
+----------------------+----------+
|starting | 0.000074 |
| checkingpermissions | 0.000083 |
| creatingtable | 0.043427 |
| Aftercreate | 0.000014 |
| queryend | 0.000003 |
| freeingitems | 0.000068 |
| loggingslow query |0.000004 |
| cleaningup | 0.000002 |
+----------------------+----------+
8 rows inset (0.00 sec)
-->查看特定部分的開銷，如CPU,SWAPS,BLOCK IO的開銷
mysql>show profile CPU,SWAPS,BLOCK IO for query 9;
+----------------------+----------+----------+------------+--------------+---------------+-------+
|Status |Duration | CPU_user | CPU_system | Block_ops_in | Block_ops_out |Swaps |
+----------------------+----------+----------+------------+--------------+---------------+-------+
|starting | 0.000074 | 0.000000 | 0.000000 | 0| 0 | 0 |
| checkingpermissions | 0.000083 | 0.000000 | 0.000000 | 0 | 0 | 0 |
| creatingtable | 0.043427 | 0.009998 | 0.017997 | 0 | 256 | 0 |
| Aftercreate | 0.000014 | 0.000000 | 0.000000 | 0 | 0 | 0 |
| queryend | 0.000003 | 0.000000 | 0.000000 | 0 | 0 | 0 |
| freeingitems | 0.000068 | 0.000000 | 0.000000 | 0 | 0 | 0 |
| loggingslow query |0.000004 | 0.000000 | 0.000000 | 0 | 0 | 0 |
| cleaningup | 0.000002 | 0.000000 | 0.000000 | 0 | 0 | 0 |
+----------------------+----------+----------+------------+--------------+---------------+-------+
8 rows inset (0.00 sec)
mysql>show profile ALL for query 9;
+----------------------+----------+----------+------------+-------------------+---------------------+--------------+---------------+---------------+-------------------+-------------------+-------------------+-------+------------------+--------------+-------------+
|Status | Duration | CPU_user | CPU_system | Context_voluntary |Context_involuntary | Block_ops_in | Block_ops_out | Messages_sent| Messages_received | Page_faults_major | Page_faults_minor | Swaps| Source_function |Source_file | Source_line |
+----------------------+----------+----------+------------+-------------------+---------------------+--------------+---------------+---------------+-------------------+-------------------+-------------------+-------+------------------+--------------+-------------+
|starting | 0.000074 | 0.000000 | 0.000000 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 3 | 0 | NULL |NULL | NULL |
| checkingpermissions | 0.000083 | 0.000000 | 0.000000 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 4 | 0 | unknown function | sql_parse.cc | 5369 |
| creatingtable | 0.043427 | 0.009998 | 0.017997 | 17 | 0 | 0 | 256 | 0 | 0 | 0 | 26 | 0 |unknown function | sql_table.cc | 3975 |
| Aftercreate | 0.000014 | 0.000000 | 0.000000 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0| 0 | unknown function | sql_table.cc | 4062 |
| queryend | 0.000003 | 0.000000 | 0.000000 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0| 0 | unknown function | sql_parse.cc | 5133 |
| freeingitems | 0.000068 | 0.000000 | 0.000000 | 0 | 0 | 0 | 0 | 0 | 0 | 0| 0 | 0 | unknown function | sql_parse.cc | 6157 |
| loggingslow query |0.000004 | 0.000000 | 0.000000 | 0 | 0 | 0 | 0 | 0 | 0 | 0| 0 | 0 | unknown function | sql_parse.cc | 1745 |
| cleaningup | 0.000002 | 0.000000 | 0.000000 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | 0 | unknown function | sql_parse.cc | 1713 |
+----------------------+----------+----------+------------+-------------------+---------------------+--------------+---------------+---------------+-------------------+-------------------+-------------------+-------+------------------+--------------+-------------+
8 rows inset (0.00 sec)