MySQL 的 SQL 語法調整主要都是使用 EXPLAIN , 但是這個並沒辦法知道詳細的 Ram(Memory)/CPU 等使用量.

於 MySQL 5.0.37 以上開始支援 MySQL Query Profiler, 可以查詢到此 SQL 會執行多少時間, 並看出 CPU/Memory 使用量, 執行過程中 System lock, Table lock 花多少時間等等.

MySQL Query Profile 詳細介紹可見: Using the New MySQL Query Profiler (2007.04.05 發表)

效能分析主要分下述三種(轉載自上篇):

Bottleneck analysis - focuses on answering the questions: What is my database server waiting on; what is a user connection waiting on; what is a piece of SQL code waiting on?

Workload analysis - examines the server and who is logged on to determine the resource usage and activity of each.

Ratio-based analysis - utilizes a number of rule-of-thumb ratios to gauge performance of a database, user connection, or piece of code.

MySQL Query Profile 使用方法

啟動

mysql> set profiling=1; # 此命令於 MySQL 會於 information_schema 的 database 建立一個 PROFILING 的 table 來紀錄.

SQL profiles show

mysql> show profiles; # 從啟動之後所有語法及使用時間, 含錯誤語法都會紀錄.

ex: (root@localhost) [test]> show profiles; # 注意 Query_ID, 下面執行時間統計等, 都是依 Query_ID 在紀錄

+----------+------------+---------------------------+

| Query_ID | Duration?? | Query???????????????????? |

+----------+------------+---------------------------+

|??????? 1 | 0.00090400 | show profile for query 1? |

|??????? 2 | 0.00008700 | select * from users?????? |

|??????? 3 | 0.00183800 | show tables?????????????? |

|??????? 4 | 0.00027600 | mysql> show profiles????? |

+----------+------------+---------------------------+

查詢所有花費時間加總

mysql> select sum(duration) from information_schema.profiling where query_id=1; # Query ID = 1

+---------------+

| sum(duration) |

+---------------+

|????? 0.000447 |

+---------------+

查詢各執行階段花費多少時間

mysql> show profile for query 1; # Query ID = 1

+--------------------+------------+

| Status???????????? | Duration?? |

+--------------------+------------+

| (initialization)?? | 0.00006300 |

| Opening tables???? | 0.00001400 |

| System lock??????? | 0.00000600 |

| Table lock???????? | 0.00001000 |

| init?????????????? | 0.00002200 |

| optimizing???????? | 0.00001100 |

| statistics???????? | 0.00009300 |

| preparing????????? | 0.00001700 |

| executing????????? | 0.00000700 |

| Sending data?????? | 0.00016800 |

| end??????????????? | 0.00000700 |

| query end????????? | 0.00000500 |

| freeing items????? | 0.00001200 |

| closing tables???? | 0.00000800 |

| logging slow query | 0.00000400 |

+--------------------+------------+

查詢各執行階段花費的各種資源列表

mysql> show profile cpu for query 1; # Query ID = 1

+--------------------------------+----------+----------+------------+

| Status???????????????????????? | Duration | CPU_user | CPU_system |

+--------------------------------+----------+----------+------------+

| (initialization)?????????????? | 0.000007 | 0??????? | 0????????? |

| checking query cache for query | 0.000071 | 0??????? | 0????????? |

| Opening tables???????????????? | 0.000024 | 0??????? | 0????????? |

| System lock??????????????????? | 0.000014 | 0??????? | 0????????? |

| Table lock???????????????????? | 0.000055 | 0.001??? | 0????????? |

| init?????????????????????????? | 0.000036 | 0??????? | 0????????? |

| optimizing???????????????????? | 0.000013 | 0??????? | 0????????? |

| statistics???????????????????? | 0.000021 | 0??????? | 0????????? |

| preparing????????????????????? | 0.00002? | 0??????? | 0????????? |

| executing????????????????????? | 0.00001? | 0??????? | 0????????? |

| Sending data?????????????????? | 0.015072 | 0.011998 | 0????????? |

| end??????????????????????????? | 0.000021 | 0??????? | 0????????? |

| query end????????????????????? | 0.000011 | 0??????? | 0????????? |

| storing result in query cache? | 0.00001? | 0??????? | 0????????? |

| freeing items????????????????? | 0.000018 | 0??????? | 0????????? |

| closing tables???????????????? | 0.000019 | 0??????? | 0????????? |

| logging slow query???????????? | 0.000009 | 0??????? | 0????????? |

+--------------------------------+----------+----------+------------+

mysql> show profile IPC for query 1;

+--------------------------------+----------+---------------+-------------------+

| Status???????????????????????? | Duration | Messages_sent | Messages_received |

+--------------------------------+----------+---------------+-------------------+

| (initialization)?????????????? | 0.000007 |???????????? 0 |???????????????? 0 |

| checking query cache for query | 0.000071 |???????????? 0 |???????????????? 0 |

| Opening tables???????????????? | 0.000024 |???????????? 0 |???????????????? 0 |

| System lock??????????????????? | 0.000014 |???????????? 0 |???????????????? 0 |

| Table lock???????????????????? | 0.000055 |???????????? 0 |???????????????? 0 |

| init?????????????????????????? | 0.000036 |???????????? 0 |???????????????? 0 |

| optimizing???????????????????? | 0.000013 |???????????? 0 |???????????????? 0 |

| statistics???????????????????? | 0.000021 |???????????? 0 |???????????????? 0 |

| preparing????????????????????? | 0.00002? |???????????? 0 |???????????????? 0 |

| executing????????????????????? | 0.00001? |???????????? 0 |???????????????? 0 |

| Sending data?????????????????? | 0.015072 |???????????? 0 |???????????????? 0 |

| end??????????????????????????? | 0.000021 |???????????? 0 |???????????????? 0 |

| query end????????????????????? | 0.000011 |???????????? 0 |???????????????? 0 |

| storing result in query cache? | 0.00001? |???????????? 0 |???????????????? 0 |

| freeing items????????????????? | 0.000018 |???????????? 0 |???????????????? 0 |

| closing tables???????????????? | 0.000019 |???????????? 0 |???????????????? 0 |

| logging slow query???????????? | 0.000009 |???????????? 0 |???????????????? 0 |

+--------------------------------+----------+---------------+-------------------+

其它屬性列表

ALL - displays all information

BLOCK IO - displays counts for block input and output operations

CONTEXT SWITCHES - displays counts for voluntary and involuntary context switches

IPC - displays counts for messages sent and received

MEMORY - is not currently implemented

PAGE FAULTS - displays counts for major and minor page faults

SOURCE - displays the names of functions from the source code, together with the name and line number of the file in which the function occurs

SWAPS - displays swap counts

設定 Profiling 存的 Size

mysql> show variables where variable_name='profiling_history_size'; # 預設是 15筆

關閉

mysql> set profiling=0;

總結

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