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;