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