mysql查詢語句最佳化工具

標籤：查詢語句最佳化工具

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把這個profiling功能開啟，可以查看sql查詢語句的整個過程中各種資源的消耗情況。

mysql> show profiles;
+----------+------------+---------------------------------+
| Query_ID | Duration   | Query                           |
+----------+------------+---------------------------------+
|        1 | 0.00049600 | show variables like "profiling" |
|        2 | 0.02267400 | show databases                  |
|        3 | 0.04235200 | SELECT DATABASE()               |
|        4 | 0.00012825 | SELECT DATABASE()               |
|        5 | 0.00025125 | show databases                  |
|        6 | 0.00145125 | show tables                     |
|        7 | 0.04207925 | show tables                     |
|        8 | 0.03485225 | select count(*) from host_item  |
+----------+------------+---------------------------------+

mysql> show profile cpu, block io  for query 8;
+----------------------+----------+----------+------------+--------------+---------------+
| Status               | Duration | CPU_user | CPU_system | Block_ops_in | Block_ops_out |
+----------------------+----------+----------+------------+--------------+---------------+
| starting             | 0.000634 | 0.000000 |   0.000000 |            0 |             0 |
| checking permissions | 0.000013 | 0.000000 |   0.000000 |            0 |             0 |
| Opening tables       | 0.000051 | 0.000000 |   0.000000 |            0 |             0 |
| System lock          | 0.000014 | 0.000000 |   0.000000 |            0 |             0 |
| init                 | 0.000015 | 0.000000 |   0.000000 |            0 |             0 |
| optimizing           | 0.033657 | 0.000000 |   0.000000 |           40 |             0 |
| statistics           | 0.000029 | 0.000000 |   0.000000 |            0 |             0 |
| preparing            | 0.000012 | 0.000000 |   0.000000 |            0 |             0 |
| executing            | 0.000006 | 0.000000 |   0.000000 |            0 |             0 |
| Sending data         | 0.000313 | 0.000000 |   0.000000 |            0 |             0 |
| end                  | 0.000008 | 0.000000 |   0.000000 |            0 |             0 |
| query end            | 0.000008 | 0.000000 |   0.000000 |            0 |             0 |
| closing tables       | 0.000047 | 0.000000 |   0.000000 |            0 |             0 |
| freeing items        | 0.000042 | 0.000000 |   0.000000 |            0 |             0 |
| logging slow query   | 0.000003 | 0.000000 |   0.000000 |            0 |             0 |
| cleaning up          | 0.000003 | 0.000000 |   0.000000 |            0 |             0 |
+----------------------+----------+----------+------------+--------------+---------------

show profile後面可以跟參數：all或者cpu,block io,page faults等。

也可以在information_schema.profiling資料庫表中直接查詢：

select state,sum(duration) as total_r,round(100*sum(duration)/(select sum(duration) from information_schema.profiling where [email protected]_id),2) as pct_r,count(*) as calls,sum(duration)/count(*) as "r/call" from information_schema.profiling where [email protected]_id group by state order by total_r desc;

最後，關閉set profiling=0該功能。

本文出自 “Victor的奮鬥曆程” 部落格，請務必保留此出處http://victor2016.blog.51cto.com/6768693/1875012

mysql查詢語句最佳化工具