MySQL中如何使用profile分析SQL执行状态

MySQL中如何使用profile分析SQL执行状态2014-10-28打开profile

mysql> select @@have_profiling;

+------------------+

| @@have_profiling |

+------------------+

| YES |

+------------------+

1 row in set （0.00 sec）

mysql> select @@profiling;

+-------------+

| @@profiling |

+-------------+

| 0 |

+-------------+

1 row in set （0.00 sec）

mysql> set session profiling=1;

Query OK, 0 rows affected （0.00 sec）

mysql> select @@profiling;

+-------------+

| @@profiling |

+-------------+

| 1 |

+-------------+

1 row in set （0.00 sec）

使用profile分析SQL，可以看到执行两次后,Send data和sending cached result to clien执行效率的变化

mysql> select count（*） from sakila.payment;

+----------+

| count（*） |

+----------+

| 16049 |

+----------+

1 row in set （0.03 sec）

mysql> show profiles;

+----------+------------+-------------------------------------+

| Query_ID | Duration | Query |

+----------+------------+-------------------------------------+

| 1 | 0.00020400 | select @@profiling |

| 2 | 0.00008900 | select count（*） from payment |

| 3 | 0.00006800 | show databaes |

| 4 | 0.02102800 | show databases |

| 5 | 0.02847600 | select count（*） from sakila.payment |

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+----------+------------+-------------------------------------+

5 rows in set （0.00 sec）

mysql> show profile for query 5;

+--------------------------------+----------+

| Status | Duration |

+--------------------------------+----------+

| starting | 0.000030 |

| Waiting for query cache lock | 0.000005 |

| checking query cache for query | 0.000043 |

| checking permissions | 0.000007 |

| Opening tables | 0.000027 |

| System lock | 0.000010 |

| Waiting for query cache lock | 0.000010 |

| init | 0.000000 |

| optimizing | 0.023255 |

| statistics | 0.000118 |

| preparing | 0.000041 |

| executing | 0.000033 |

| Sending data | 0.003833 |

| end | 0.000054 |

| query end | 0.000045 |

| closing tables | 0.000045 |

| freeing items | 0.000072 |

| Waiting for query cache lock | 0.000033 |

| freeing items | 0.000785 |

| Waiting for query cache lock | 0.000016 |

| freeing items | 0.000002 |

| storing result in query cache | 0.000005 |

| logging slow query | 0.000003 |

| cleaning up | 0.000004 |

+--------------------------------+----------+

24 rows in set （0.00 sec）

mysql> select count（*） from sakila.payment;

+----------+

| count（*） |

+----------+

| 16049 |

+----------+

1 row in set （0.00 sec）

mysql> show profiles;

+----------+------------+-------------------------------------+

| Query_ID | Duration | Query |

+----------+------------+-------------------------------------+

| 1 | 0.00020400 | select @@profiling |

| 2 | 0.00008900 | select count（*） from payment |

| 3 | 0.00006800 | show databaes |

| 4 | 0.02102800 | show databases |

| 5 | 0.02847600 | select count（*） from sakila.payment |

| 6 | 0.00006900 | select count（*） from sakila.payment |

+----------+------------+-------------------------------------+

6 rows in set （0.00 sec）

mysql> show profile for query 6;

+--------------------------------+----------+

| Status | Duration |

+--------------------------------+----------+

| starting | 0.000029 |

| Waiting for query cache lock | 0.000004 |

| checking query cache for query | 0.000007 |

| checking privileges on cached | 0.000004 |

| checking permissions | 0.000008 |

| sending cached result to clien | 0.000012 |

| logging slow query | 0.000002 |

| cleaning up | 0.000003 |

+--------------------------------+----------+

8 rows in set （0.00 sec）