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;

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