mysql -> show profile ;

mysql用于分析sql的性能。可以使用explain以及profile。下面是show profile 详解。

This section does not apply to MySQL Enterprise Server users.

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

The SHOW PROFILES and SHOW PROFILE statements display profiling information that indicates resource usage for statements executed during the course of the current session.

Profiling is controlled by the profiling session variable, which has a default value of 0 (OFF). Profiling is enabled by setting profiling to 1 or ON:

mysql> SET profiling = 1;

SHOW PROFILES displays a list of the most recent statements sent to the master. The size of the list is controlled by the profiling_history_size session variable, which has a default value of 15. The maximum value is 100. Setting the value to 0 has the practical effect of disabling profiling.

All statements are profiled except SHOW PROFILES and SHOW PROFILE, so you will find neither of those statements in the profile list. Malformed statements are profiled. For example, SHOW PROFILING is an illegal statement, and a syntax error occurs if you try to execute it, but it will show up in the profiling list.

SHOW PROFILE displays detailed information about a single statement. Without the FOR QUERY n clause, the output pertains to the most recently executed statement. If FOR QUERY n is included, SHOW PROFILE displays information for statement n. The values of n correspond to the Query_ID values displayed by SHOW PROFILES.

The LIMIT row_count clause may be given to limit the output to row_count rows. If LIMIT is given, OFFSET offset may be added to begin the output offset rows into the full set of rows.

By default, SHOW PROFILE displays Status and Duration columns. The Status values are like the State values displayed by SHOW PROCESSLIST, although there might be some minor differences in interpretion for the two statements for some status values (see Section 7.10, “Examining Thread Information”).

Optional type values may be specified to display specific additional types of information:

ALL displays all information

BLOCK IO displays counts for block input and output operations

CONTEXT SWITCHES displays counts for voluntary and involuntary context switches

CPU displays user and system CPU usage times

IPC displays counts for messages sent and received

MEMORY is not currently implemented

PAGE FAULTS displays counts for major and minor page faults

SOURCE displays the names of functions from the source code, together with the name and line number of the file in which the function occurs

SWAPS displays swap counts

Profiling is enabled per session. When a session ends, its profiling information is lost.

mysql> SELECT @@profiling;

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

| @@profiling |

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

|           0 |

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

1 row in set (0.00 sec)

mysql> SET profiling = 1;

Query OK, 0 rows affected (0.00 sec)

mysql> DROP TABLE IF EXISTS t1;

Query OK, 0 rows affected, 1 warning (0.00 sec)

mysql> CREATE TABLE T1 (id INT);

Query OK, 0 rows affected (0.01 sec)

mysql> SHOW PROFILES;

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

| Query_ID | Duration | Query                    |

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

|        0 | 0.000088 | SET PROFILING = 1        |

|        1 | 0.000136 | DROP TABLE IF EXISTS t1  |

|        2 | 0.011947 | CREATE TABLE t1 (id INT) |

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

3 rows in set (0.00 sec)

mysql> SHOW PROFILE;

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

| Status               | Duration |

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

| checking permissions | 0.000040 |

| creating table       | 0.000056 |

| After create         | 0.011363 |

| query end            | 0.000375 |

| freeing items        | 0.000089 |

| logging slow query   | 0.000019 |

| cleaning up          | 0.000005 |

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

7 rows in set (0.00 sec)

mysql> SHOW PROFILE FOR QUERY 1;

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

| Status             | Duration |

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

| query end          | 0.000107 |

| freeing items      | 0.000008 |

| logging slow query | 0.000015 |

| cleaning up        | 0.000006 |

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

4 rows in set (0.00 sec)

mysql> SHOW PROFILE CPU FOR QUERY 2;

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

| Status               | Duration | CPU_user | CPU_system |

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

| checking permissions | 0.000040 | 0.000038 |   0.000002 |

| creating table       | 0.000056 | 0.000028 |   0.000028 |

| After create         | 0.011363 | 0.000217 |   0.001571 |

| query end            | 0.000375 | 0.000013 |   0.000028 |

| freeing items        | 0.000089 | 0.000010 |   0.000014 |

| logging slow query   | 0.000019 | 0.000009 |   0.000010 |

| cleaning up          | 0.000005 | 0.000003 |   0.000002 |

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

7 rows in set (0.00 sec)

Note

Profiling is only partially functional on some architectures. For values that depend on the getrusage() system call, NULL is returned on systems such as Windows that do not support the call. In addition, profiling is per process and not per thread. This means that activity on threads within the server other than your own may affect the timing information that you see.

SHOW PROFILES and SHOW PROFILE were added in MySQL 5.0.37.

You can also get profiling information from the PROFILING table in INFORMATION_SCHEMA. See Section 18.17, “The INFORMATION_SCHEMA PROFILING Table”. For example, the following queries produce the same result:

SHOW PROFILE FOR QUERY 2;

SELECT STATE, FORMAT(DURATION, 6) AS DURATION

FROM INFORMATION_SCHEMA.PROFILING

WHERE QUERY_ID = 2 ORDER BY SEQ;

Important

Please note that the SHOW PROFILE and SHOW PROFILES functionality is part of the MySQL 5.0 Community Server only.