剖析单条查询 profile:

mysql> show variables like '%prof%';
+------------------------+-------+
| Variable_name| Value |
+------------------------+-------+
| have_profiling | YES |
| profiling| OFF |
| profiling_history_size | 15|
+------------------------+-------+
3 rows in set (0.00 sec)

mysql> setprofiling = 1;
Query OK, 0 rows affected, 1 warning (0.00 sec)

mysql> show variables like '%prof%';
+------------------------+-------+
| Variable_name| Value |
+------------------------+-------+
| have_profiling | YES |
| profiling| ON|
| profiling_history_size | 15|
+------------------------+-------+
3 rows in set (0.00 sec)

mysql> use mysql;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A

Database changed
mysql> select count(*) from user;
+----------+
| count(*) |
+----------+
|4 |
+----------+
1 row in set (0.03 sec)

mysql> show profiles;
+----------+------------+------------------------------+
| Query_ID | Duration | Query|
+----------+------------+------------------------------+
|1 | 0.00103425 | show variables like '%prof%' |
|2 | 0.00016325 | SELECT DATABASE()|
|3 | 0.00049450 | show databases |
|4 | 0.00039775 | show tables|
|5 | 0.02702100 | select count(*) from user|
+----------+------------+------------------------------+
5 rows in set, 1 warning (0.00 sec)

mysql> show profile for query 5;
+----------------------+----------+
| Status | Duration |
+----------------------+----------+
| starting | 0.000090 |
| checking permissions | 0.000012 |
| Opening tables | 0.000030 |
| init | 0.000035 |
| System lock| 0.000016 |
| optimizing | 0.025417 |
| executing| 0.000054 |
| end| 0.000551 |
| query end| 0.000020 |
| closing tables | 0.000021 |
| freeing items| 0.000732 |
| cleaning up| 0.000045 |
+----------------------+----------+
12 rows in set, 1 warning (0.00 sec)