最近网站的数据量一直在上升，有些表达到了千条以上，那是一个慢啊。
还是分析下SQL的问题吧！手动分析，只能看到网上说的那些优化方法。
但是瓶颈在那里呢？可以使用explain 的方式解决，但是还是感觉explain 不够详细。
mysql5.0.37版本以上支持了，profiling ，据说是Jeremy Cole捐献给MySQL社区版本。
profiling 功能可以了解到sql语句消耗资源的更详细的信息。
show profile 的格式如下：
SHOW PROFILE [type [, type] … ]
[FOR QUERY n]
[LIMIT row_count [OFFSET offset]]
type:
ALL
| BLOCK IO
| CONTEXT SWITCHES
| CPU
| IPC
| MEMORY
| PAGE FAULTS
| SOURCE
| SWAPS
该方式默认是关闭的。
可以通过以下语句查看
打开功能
mysql>set profiling=1;
执行需要测试的sql 语句：
select inet_ntoa(visit_net) visit_net,sum(totalbytes) as totalbytes,sum(inbytes) as inbytes,sum(totalbytes)-sum(inbytes) as outbytes from
( select * from businessflow where userid=9 ) aa
group by visit_net order by totalbytes DESC limit 0,3
mysql> show profilesG;
通过指定的Query_ID 来查询指定的sql语句的执行信息：
mysql> show profile for query 1;
+——————————–+———-+
| Status | Duration |
+——————————–+———-+
| starting | 0.000021 |
| checking query cache for query | 0.000085 |
| Opening tables | 0.000036 |
| System lock | 0.000007 |
| Table lock | 0.000071 |
| optimizing | 0.000012 |
| statistics | 0.000013 |
| preparing | 0.000013 |
| executing | 0.000005 |
| Sending data | 0.592819 |
| converting HEAP to myisam | 0.026474 |
| Sending data | 0.215715 |
| init | 0.000029 |
| storing result in query cache | 0.000012 |
| optimizing | 0.000005 |
| statistics | 0.000011 |
| preparing | 0.000008 |
| Creating tmp table | 0.000038 |
| executing | 0.000004 |
| Copying to tmp table | 0.235759 |
| converting HEAP to MyISAM | 1.020230 |
| Copying to tmp table on disk | 0.166174 |
| Sorting result | 0.056304 |
| Sending data | 0.000053 |
| end | 0.000004 |
| removing tmp table | 0.003539 |
| end | 0.000008 |
| query end | 0.000004 |
| freeing items | 0.000036 |
| removing tmp table | 0.004107 |
| closing tables | 0.000009 |
| logging slow query | 0.000004 |
| cleaning up | 0.000004 |
+——————————–+———-+
33 rows in set (0.00 sec)
mysql> show profile cpu for query 1;
+——————————–+———-+———-+————+
| Status | Duration | CPU_user | CPU_system |
+——————————–+———-+———-+————+
| starting | 0.000021 | 0.000000 | 0.000000 |
| checking query cache for query | 0.000085 | 0.000000 | 0.000000 |
| Opening tables | 0.000036 | 0.000000 | 0.000000 |
| System lock | 0.000007 | 0.000000 | 0.000000 |
| Table lock | 0.000071 | 0.000000 | 0.000000 |
| optimizing | 0.000012 | 0.000000 | 0.000000 |
| statistics | 0.000013 | 0.000000 | 0.000000 |
| preparing | 0.000013 | 0.000000 | 0.000000 |
| executing | 0.000005 | 0.000000 | 0.000000 |
| Sending data | 0.592819 | 0.592037 | 0.000000 |
| converting HEAP to MyISAM | 0.026474 | 0.000000 | 0.020002 |
| Sending data | 0.215715 | 0.212014 | 0.008000 |
| init | 0.000029 | 0.000000 | 0.000000 |
| storing result in query cache | 0.000012 | 0.000000 | 0.000000 |
| optimizing | 0.000005 | 0.000000 | 0.000000 |
| statistics | 0.000011 | 0.000000 | 0.000000 |
| preparing | 0.000008 | 0.000000 | 0.000000 |
| Creating tmp table | 0.000038 | 0.000000 | 0.000000 |
| executing | 0.000004 | 0.000000 | 0.000000 |
| Copying to tmp table | 0.235759 | 0.240015 | 0.000000 |
| converting HEAP to MyISAM | 1.020230 | 0.988061 | 0.032002 |
| Copying to tmp table on disk | 0.166174 | 0.160010 | 0.000000 |
| Sorting result | 0.056304 | 0.052004 | 0.008001 |
| Sending data | 0.000053 | 0.000000 | 0.000000 |
| end | 0.000004 | 0.000000 | 0.000000 |
| removing tmp table | 0.003539 | 0.000000 | 0.000000 |
| end | 0.000008 | 0.000000 | 0.000000 |
| query end | 0.000004 | 0.000000 | 0.000000 |
| freeing items | 0.000036 | 0.000000 | 0.000000 |
| removing tmp table | 0.004107 | 0.000000 | 0.008000 |
| closing tables | 0.000009 | 0.000000 | 0.000000 |
| logging slow query | 0.000004 | 0.000000 | 0.000000 |
| cleaning up | 0.000004 | 0.000000 | 0.000000 |
+——————————–+———-+———-+————+
33 rows in set (0.00 sec)
从上上面可以看到，
| Sending data | 0.592819 |
| converting HEAP to MyISAM | 0.026474 |
| Sending data | 0.215715 |
| Copying to tmp table | 0.235759 |
| converting HEAP to MyISAM | 1.020230 |
| Copying to tmp table on disk | 0.166174 |
以上几项 耗时较长，所以考虑把该表转换为MyISAM 以供查询提高速度。并且提高的值
测试完毕以后 ，关闭参数：
mysql> set profiling=0
再次打开程序，发现等待速度降低。问题有所好转。
参考：http://dev.mysql.com/doc/refman/5.0/en/show-profiles.html