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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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