MySQL中使用SHOW PROFILE命令分析性能的用法整理

更新時(shí)間：2015年11月11日 12:01:25 投稿：goldensun

這篇文章主要介紹了MySQL中使用show profile命令分析性能的用法整理,show profiles是數(shù)據(jù)庫性能優(yōu)化的常用命令,需要的朋友可以參考下

show profile是由Jeremy Cole捐獻(xiàn)給MySQL社區(qū)版本的。默認(rèn)的是關(guān)閉的，但是會(huì)話級別可以開啟這個(gè)功能。開啟它可以讓MySQL收集在執(zhí)行語句的時(shí)候所使用的資源。為了統(tǒng)計(jì)報(bào)表,把profiling設(shè)為1

mysql> SET profiling = 1;

之后在運(yùn)行一個(gè)查詢

mysql> SELECT COUNT(DISTINCT actor.first_name) AS cnt_name, COUNT(*) AS cnt
-> FROM sakila.film_actor
-> INNER JOIN sakila.actor USING(actor_id)
-> GROUP BY sakila.film_actor.film_id
-> ORDER BY cnt_name DESC;
...
997 rows in set (0.03 sec)

這個(gè)執(zhí)行語句的剖析信息存儲(chǔ)在這個(gè)會(huì)話中。使用SHOW PROFILES進(jìn)行查看。

mysql> SHOW PROFILES\G

*************************** 1. row ***************************
Query_ID: 1
Duration: 0.02596900
Query: SELECT COUNT(DISTINCT actor.first_name) AS cnt_name,...

你可以使用SHOW PROFILE語句來獲取已經(jīng)存儲(chǔ)的剖析數(shù)據(jù)。如果不加參數(shù)，會(huì)顯示狀態(tài)以及它們持續(xù)的時(shí)間。

mysql> SHOW PROFILE;

+------------------------+-----------+
| Status | Duration |
+------------------------+-----------+
| (initialization) | 0.000005 |
| Opening tables | 0.000033 |
| System lock | 0.000037 |
| Table lock | 0.000024 |
| init | 0.000079 |
| optimizing | 0.000024 |
| statistics | 0.000079 |
| preparing | 0.00003 |
| Creating tmp table | 0.000124 |
| executing | 0.000008 |
| Copying to tmp table | 0.010048 |
| Creating sort index | 0.004769 |
| Copying to group table | 0.0084880 |
| Sorting result | 0.001136 |
| Sending data | 0.000925 |
| end | 0.00001 |
| removing tmp table | 0.00004 |
| end | 0.000005 |
| removing tmp table | 0.00001 |
| end | 0.000011 |
| query end | 0.00001 |
| freeing items | 0.000025 |
| removing tmp table | 0.00001 |
| freeing items | 0.000016 |
| closing tables | 0.000017 |
| logging slow query | 0.000006 |
+------------------------+-----------+

每行都是狀態(tài)變化的過程以及它們持續(xù)的時(shí)間。Status那一列和SHOW FULL PROCESSLIST的State應(yīng)該是一致的。
這個(gè)值是來自于thd->proc_info變量。因此你所查看的這個(gè)值是直接來自MySQL內(nèi)部的。盡管這些數(shù)值是比較直接易懂的，你也可以查看MySQL手冊。

你可以給SHOW PROFILES指定一個(gè)Query_ID來查看指定的語句，還可以給輸出添加新的列。如，查看用戶和CPU使用。可以用如下命令。

mysql> SHOW PROFILE CPU FOR QUERY 1;

SHOW PROFILE可以深入的查看服務(wù)器執(zhí)行語句的工作情況。以及也能幫助你理解執(zhí)行語句消耗時(shí)間的情況。一些限制是它沒有實(shí)現(xiàn)的功能，不能查看和剖析其他連接的語句，以及剖析時(shí)所引起的消耗。

SHOW PROFILES顯示最近發(fā)給服務(wù)器的多條語句，條數(shù)根據(jù)會(huì)話變量profiling_history_size定義，默認(rèn)是15，最大值為100。設(shè)為0等價(jià)于關(guān)閉分析功能。

SHOW PROFILE FOR QUERY n，這里的n就是對應(yīng)SHOW PROFILES輸出中的Query_ID。

例如：

mysql> show profiles;

+----------+-------------+---------------------------------------+
| Query_ID | Duration | Query     |
+----------+-------------+---------------------------------------+
| 1 | 0.00037700 | alter table table1 drop column c3 int |
| 2 | 70.37123800 | alter table table1 drop column c3 |
| 3 | 0.00124500 | show tables    |
| 4 | 0.00569800 | select * from table1 where id=2 |
| 5 | 0.00068500 | select count(1) from tables1  |
| 6 | 0.00197900 | select count(1) from table1  |
| 7 | 0.00105900 | alter table tables1 drop c1  |
| 8 | 0.00800200 | alter table table1 drop c1  |
+----------+-------------+---------------------------------------+
8 rows in set (0.00 sec)

mysql> SHOW PROFILE FOR QUERY 2; #查看alter table table1 drop column c3的分析

+------------------------------+-----------+
| Status   | Duration |
+------------------------------+-----------+
| starting   | 0.000183 |
| checking permissions  | 0.000057 |
| checking permissions  | 0.000059 |
| init    | 0.000060 |
| Opening tables  | 0.000071 |
| System lock   | 0.000062 |
| setup   | 0.000080 |
| creating table  | 0.005052 |
| After create   | 0.000220 |
| copy to tmp table  | 0.000244 |
| rename result table  | 70.364027 |
| end    | 0.000575 |
| Waiting for query cache lock | 0.000062 |
| end    | 0.000075 |
| query end   | 0.000057 |
| closing tables  | 0.000061 |
| freeing items  | 0.000080 |
| logging slow query  | 0.000056 |
| logging slow query  | 0.000098 |
| cleaning up   | 0.000059 |
+------------------------------+-----------+
20 rows in set (0.00 sec)

如果沒有指定FOR QUERY，那么輸出最近一條語句的信息。

LIMIT部分的用法與SELECT中LIMIT子句一致，不贅述。

type是可選的，取值范圍可以如下：

ALL 顯示所有性能信息
BLOCK IO 顯示塊IO操作的次數(shù)
CONTEXT SWITCHES 顯示上下文切換次數(shù)，不管是主動(dòng)還是被動(dòng)
CPU 顯示用戶CPU時(shí)間、系統(tǒng)CPU時(shí)間
IPC 顯示發(fā)送和接收的消息數(shù)量
MEMORY [暫未實(shí)現(xiàn)]
PAGE FAULTS 顯示頁錯(cuò)誤數(shù)量
SOURCE 顯示源碼中的函數(shù)名稱與位置
SWAPS 顯示SWAP的次數(shù)

例：

mysql> show profile cpu for query 2;

+------------------------------+-----------+----------+------------+
| Status   | Duration | CPU_user | CPU_system |
+------------------------------+-----------+----------+------------+
| starting   | 0.000183 | 0.000000 | 0.000000 |
| checking permissions  | 0.000057 | 0.000000 | 0.000000 |
| checking permissions  | 0.000059 | 0.000000 | 0.000000 |
| init    | 0.000060 | 0.000000 | 0.000000 |
| Opening tables  | 0.000071 | 0.000000 | 0.000000 |
| System lock   | 0.000062 | 0.000000 | 0.000000 |
| setup   | 0.000080 | 0.000000 | 0.001000 |
| creating table  | 0.005052 | 0.003000 | 0.001000 |
| After create   | 0.000220 | 0.000000 | 0.000000 |
| copy to tmp table  | 0.000244 | 0.000000 | 0.000000 |
| rename result table  | 70.364027 | 7.470864 | 41.612674 |
| end    | 0.000575 | 0.000000 | 0.001000 |
| Waiting for query cache lock | 0.000062 | 0.000000 | 0.000000 |
| end    | 0.000075 | 0.000000 | 0.000000 |
| query end   | 0.000057 | 0.000000 | 0.000000 |
| closing tables  | 0.000061 | 0.000000 | 0.000000 |
| freeing items  | 0.000080 | 0.000000 | 0.000000 |
| logging slow query  | 0.000056 | 0.000000 | 0.000000 |
| logging slow query  | 0.000098 | 0.000000 | 0.000000 |
| cleaning up   | 0.000059 | 0.000000 | 0.000000 |
+------------------------------+-----------+----------+------------+
20 rows in set (0.00 sec)

ps:
SHOW PROFILE ALL FOR QUERY 2;的信息還可以通過SELECT * FROM information_schema.profiling WHERE query_id = 2 ORDER BY seq;獲取。

作用范圍
這個(gè)命令只是在本會(huì)話內(nèi)起作用，即無法分析本會(huì)話外的語句。

開啟分析功能后，所有本會(huì)話中的語句都被分析（甚至包括執(zhí)行錯(cuò)誤的語句），除了SHOW PROFILE和SHOW PROFILES兩句本身。

應(yīng)用示例：使用SHOW PROFILE分析查詢緩存命中的性能優(yōu)勢。

mysql> set profiling=1;

Query OK, 0 rows affected (0.00 sec)

mysql> select count(1) as cnt from tran_excution;

+-------+
| cnt |
+-------+
| 14225 |
+-------+
1 row in set (0.00 sec)

由于已經(jīng)啟用了查詢緩存，相同查詢（非分區(qū)表）可以直接在查詢緩存中命中。

mysql> select count(1) as cnt from tran_excution;

我們仔細(xì)看下兩個(gè)同樣的語句的分析。

mysql> show profile source for query 1;

+--------------------------------+----------+-----------------------+---------------+-------------+
| Status    | Duration | Source_function | Source_file | Source_line |
+--------------------------------+----------+-----------------------+---------------+-------------+
| starting   | 0.000048 | NULL   | NULL  | NULL |
| Waiting for query cache lock | 0.000013 | try_lock  | sql_cache.cc |  454 |
| checking query cache for query | 0.000040 | send_result_to_client | sql_cache.cc | 1561 |
| checking permissions  | 0.000023 | check_access  | sql_parse.cc | 4751 |
| Opening tables   | 0.000040 | open_tables  | sql_base.cc | 4831 |
| System lock   | 0.000020 | mysql_lock_tables | lock.cc |  299 |
| Waiting for query cache lock | 0.000037 | try_lock  | sql_cache.cc |  454 |
| init    | 0.000020 | mysql_select  | sql_select.cc | 2579 |
| optimizing   | 0.000015 | optimize  | sql_select.cc |  865 |
| statistics   | 0.000017 | optimize  | sql_select.cc | 1056 |
| preparing   | 0.000016 | optimize  | sql_select.cc | 1078 |
| executing   | 0.000015 | exec   | sql_select.cc | 1836 |
| Sending data   | 0.003875 | exec   | sql_select.cc | 2380 |
| end    | 0.000018 | mysql_select  | sql_select.cc | 2615 |
| query end   | 0.000015 | mysql_execute_command | sql_parse.cc | 4440 |
| closing tables   | 0.000016 | mysql_execute_command | sql_parse.cc | 4492 |
| freeing items   | 0.000016 | mysql_parse  | sql_parse.cc | 5640 |
| Waiting for query cache lock | 0.000012 | try_lock  | sql_cache.cc |  454 |
| freeing items   | 0.000032 | NULL   | NULL  | NULL |
| Waiting for query cache lock | 0.000017 | try_lock  | sql_cache.cc |  454 |
| freeing items   | 0.000016 | NULL   | NULL  | NULL |
| storing result in query cache | 0.000017 | end_of_result  | sql_cache.cc | 1020 |
| logging slow query  | 0.000018 | log_slow_statement | sql_parse.cc | 1461 |
| logging slow query  | 0.000050 | log_slow_statement | sql_parse.cc | 1470 |
| cleaning up   | 0.000018 | dispatch_command | sql_parse.cc | 1417 |
+--------------------------------+----------+-----------------------+---------------+-------------+
25 rows in set (0.00 sec)

mysql> show profile source for query 2;

+--------------------------------+----------+-----------------------+--------------+-------------+
| Status    | Duration | Source_function | Source_file | Source_line |
+--------------------------------+----------+-----------------------+--------------+-------------+
| starting   | 0.000051 | NULL   | NULL  | NULL |
| Waiting for query cache lock | 0.000014 | try_lock  | sql_cache.cc |  454 |
| checking query cache for query | 0.000016 | send_result_to_client | sql_cache.cc | 1561 |
| checking privileges on cached | 0.000013 | send_result_to_client | sql_cache.cc | 1652 |
| checking permissions  | 0.000015 | check_access  | sql_parse.cc | 4751 |
| sending cached result to clien | 0.000036 | send_result_to_client | sql_cache.cc | 1749 |
| logging slow query  | 0.000017 | log_slow_statement | sql_parse.cc | 1461 |
| cleaning up   | 0.000018 | dispatch_command | sql_parse.cc | 1417 |
+--------------------------------+----------+-----------------------+--------------+-------------+
8 rows in set (0.00 sec)

可以清晰地看到緩存中命中時(shí)，大大節(jié)省了后臺(tái)的開銷。當(dāng)然緩存的使用也需要根據(jù)各種場景（表的數(shù)據(jù)規(guī)模，更新頻率等）考察使用，并不是啟用緩存就一定能夠提高查詢效率。這里僅僅作為SHOW PROFILE的一個(gè)應(yīng)用示例。

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