varchar 所占内存的影响 测试_MySQL

准备数据

sysbench --test=oltp --oltp-nontrx-mode=update_key --mysql-table-engine=innodb --oltp-table-size=1000000 --mysql-socket=/tmp/mysql3392.sock --mysql-user=dba --mysql-host=localhost --mysql-password=localdba --db-driver=mysql --mysql-db=test prepare

mysql> desc sbtest;

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

| Field | Type             | Null | Key | Default | Extra          |

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

| id    | int(10) unsigned | NO   | PRI | NULL    | auto_increment |

| k     | int(10) unsigned | NO   | MUL | 0       |                |

| c     | char(120)        | NO   |     |         |                |

| pad   | char(60)         | NO   |     |         |                |

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

mysql> select count(c) from sbtest;

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

| count(c) |

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

|  1000000 |

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

mysql> desc select * from sbtest order by pad;

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

| id | select_type | table  | type | possible_keys | key  | key_len | ref  | rows    | Extra          |

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

|  1 | SIMPLE      | sbtest | ALL  | NULL          | NULL | NULL    | NULL | 1000126 | Using filesort |

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

mysql> set profiling = 1;

Query OK, 0 rows affected (0.00 sec)

mysql> select count(*) from sbtest order by pad;     

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

| count(*) |

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

|  1000000 |

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

1 row in set (0.53 sec)

mysql> show profiles;

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

| Query_ID | Duration   | Query                                    |

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

|        1 | 0.53102850 | select count(*) from sbtest order by pad |

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

1 row in set (0.02 sec)

mysql> show profile cpu,block io for query 1;

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

| Status               | Duration | CPU_user | CPU_system | Block_ops_in | Block_ops_out |

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

| starting             | 0.000127 | 0.000000 |   0.000000 |            0 |             0 |

| checking permissions | 0.000017 | 0.000000 |   0.000000 |            0 |             0 |

| Opening tables       | 0.000042 | 0.000000 |   0.000000 |            0 |             0 |

| System lock          | 0.000022 | 0.000000 |   0.000000 |            0 |             0 |

| init                 | 0.000038 | 0.000000 |   0.000000 |            0 |             0 |

| optimizing           | 0.000011 | 0.000000 |   0.000000 |            0 |             0 |

| statistics           | 0.000022 | 0.000000 |   0.000000 |            0 |             0 |

| preparing            | 0.000017 | 0.000000 |   0.000000 |            0 |             0 |

| executing            | 0.000014 | 0.000000 |   0.000000 |            0 |             0 |

| Sending data         | 0.530471 | 0.502923 |   0.018997 |           32 |             0 |

| end                  | 0.000034 | 0.000000 |   0.000000 |            0 |             0 |

| query end            | 0.000010 | 0.000000 |   0.000000 |            0 |             0 |

| closing tables       | 0.000025 | 0.000000 |   0.000000 |            0 |             0 |

| freeing items        | 0.000037 | 0.000000 |   0.000000 |            0 |             0 |

| logging slow query   | 0.000004 | 0.000000 |   0.000000 |            0 |             0 |

| logging slow query   | 0.000128 | 0.000000 |   0.000000 |            0 |             8 |

| cleaning up          | 0.000012 | 0.000000 |   0.000000 |            0 |             0 |

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

/////char change to varchar

mysql> alter table sbtest change pad pad varchar(60);

Query OK, 1000000 rows affected (10.72 sec)

Records: 1000000  Duplicates: 0  Warnings: 0

mysql> select pad from sbtest limit 30;

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

| pad                                                |

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

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| qqqqqqqqqqwwwwwwwwwweeeeeeeeeerrrrrrrrrrtttttttttt |

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mysql> desc sbtest;

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

| Field | Type             | Null | Key | Default | Extra          |

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

| id    | int(10) unsigned | NO   | PRI | NULL    | auto_increment |

| k     | int(10) unsigned | NO   | MUL | 0       |                |

| c     | char(120)        | NO   |     |         |                |

| pad   | varchar(60)      | YES  |     | NULL    |                |

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

＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝无索引的情况下：＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝

mysql> desc  select * from sbtest order by pad;

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

| id | select_type | table  | type | possible_keys | key  | key_len | ref  | rows    | Extra          |

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

|  1 | SIMPLE      | sbtest | ALL  | NULL          | NULL | NULL    | NULL | 1000117 | Using filesort |

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

mysql> select count(*) from sbtest order by pad;

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

| count(*) |

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

|  1000000 |

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

1 row in set (0.51 sec)

mysql> show profile cpu,block io for query 11;

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

| Status               | Duration | CPU_user | CPU_system | Block_ops_in | Block_ops_out |

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

| starting             | 0.000081 | 0.000000 |   0.000000 |            0 |             0 |

| checking permissions | 0.000014 | 0.000000 |   0.000000 |            0 |             0 |

| Opening tables       | 0.000033 | 0.000000 |   0.000000 |            0 |             0 |

| System lock          | 0.000025 | 0.000000 |   0.000000 |            0 |             0 |

| init                 | 0.000028 | 0.000000 |   0.000000 |            0 |             0 |

| optimizing           | 0.000009 | 0.000000 |   0.000000 |            0 |             0 |

| statistics           | 0.000019 | 0.000000 |   0.000000 |            0 |             0 |

| preparing            | 0.000013 | 0.000000 |   0.000000 |            0 |             0 |

| executing            | 0.000011 | 0.000000 |   0.000000 |            0 |             0 |

| Sending data         | 0.506327 | 0.489925 |   0.018997 |            0 |             0 |

| end                  | 0.000026 | 0.001000 |   0.000000 |            0 |             0 |

| query end            | 0.000010 | 0.000000 |   0.000000 |            0 |             0 |

| closing tables       | 0.000022 | 0.000000 |   0.000000 |            0 |             0 |

| freeing items        | 0.000034 | 0.000000 |   0.000000 |            0 |             0 |

| logging slow query   | 0.000003 | 0.000000 |   0.000000 |            0 |             0 |

| logging slow query   | 0.000114 | 0.000000 |   0.000000 |            0 |             8 |

| cleaning up          | 0.000009 | 0.000000 |   0.000000 |            0 |             0 |

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

varchar(120)的情况下：

mysql> alter table sbtest change pad pad varchar(120);

Query OK, 1000000 rows affected (11.77 sec)

Records: 1000000  Duplicates: 0  Warnings: 0

mysql> desc sbtest;

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

| Field | Type             | Null | Key | Default | Extra          |

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

| id    | int(10) unsigned | NO   | PRI | NULL    | auto_increment |

| k     | int(10) unsigned | NO   | MUL | 0       |                |

| c     | char(120)        | NO   |     |         |                |

| pad   | varchar(120)     | YES  |     | NULL    |                |

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

mysql> desc select * from sbtest;

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

| id | select_type | table  | type | possible_keys | key  | key_len | ref  | rows    | Extra |

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

|  1 | SIMPLE      | sbtest | ALL  | NULL          | NULL | NULL    | NULL | 1000117 |       |

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

1 row in set (0.00 sec)

mysql> desc select count(*) from sbtest;

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

| id | select_type | table  | type  | possible_keys | key  | key_len | ref  | rows    | Extra       |

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

|  1 | SIMPLE      | sbtest | index | NULL          | k    | 4       | NULL | 1000117 | Using index |

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

1 row in set (0.00 sec)

mysql> select count(*) from sbtest order by pad;

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

| count(*) |

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

|  1000000 |

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

1 row in set (0.51 sec)

mysql> show profile cpu,block io for query 17;

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

| Status               | Duration | CPU_user | CPU_system | Block_ops_in | Block_ops_out |

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

| starting             | 0.000073 | 0.000000 |   0.000000 |            0 |             0 |

| checking permissions | 0.000013 | 0.000000 |   0.000000 |            0 |             0 |

| Opening tables       | 0.000031 | 0.000000 |   0.000000 |            0 |             0 |

| System lock          | 0.000024 | 0.000000 |   0.000000 |            0 |             0 |

| init                 | 0.000026 | 0.000000 |   0.000000 |            0 |             0 |

| optimizing           | 0.000008 | 0.000000 |   0.000000 |            0 |             0 |

| statistics           | 0.000019 | 0.000000 |   0.000000 |            0 |             0 |

| preparing            | 0.000013 | 0.000000 |   0.000000 |            0 |             0 |

| executing            | 0.000011 | 0.000000 |   0.000000 |            0 |             0 |

| Sending data         | 0.510981 | 0.491925 |   0.018997 |            0 |             0 |

| end                  | 0.000025 | 0.000000 |   0.000000 |            0 |             0 |

| query end            | 0.000013 | 0.000000 |   0.000000 |            0 |             0 |

| closing tables       | 0.000026 | 0.000000 |   0.000000 |            0 |             0 |

| freeing items        | 0.000039 | 0.000000 |   0.000000 |            0 |             0 |

| logging slow query   | 0.000004 | 0.000000 |   0.000000 |            0 |             0 |

| logging slow query   | 0.000110 | 0.000000 |   0.000000 |            0 |             8 |

| cleaning up          | 0.000007 | 0.000000 |   0.000000 |            0 |             0 |

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

＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝有索引的情况下：＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝

alter table sbtest change pad pad varchar(60);

mysql> alter table sbtest add key(pad);

Query OK, 0 rows affected (7.60 sec)

Records: 0  Duplicates: 0  Warnings: 0

mysql> show index from sbtest;

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

| Table  | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |

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

| sbtest |          0 | PRIMARY  |            1 | id          | A         |     1000117 |     NULL | NULL   |      | BTREE      |         |               |

| sbtest |          1 | k        |            1 | k           | A         |           6 |     NULL | NULL   |      | BTREE      |         |               |

| sbtest |          1 | pad      |            1 | pad         | A         |         200 |     NULL | NULL   | YES  | BTREE      |         |               |

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

varchar(60)

mysql> desc select count(*) from sbtest order by pad;

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

| id | select_type | table  | type  | possible_keys | key  | key_len | ref  | rows    | Extra       |

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

|  1 | SIMPLE      | sbtest | index | NULL          | pad  | 183     | NULL | 1000117 | Using index |

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

mysql> select count(*) from sbtest order by pad;

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

| count(*) |

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

|  1000000 |

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

1 row in set (0.44 sec)

mysql> show profile cpu,block io for query 1

    -> ;

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

| Status               | Duration | CPU_user | CPU_system | Block_ops_in | Block_ops_out |

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

| starting             | 0.000115 | 0.000000 |   0.000000 |            0 |             0 |

| checking permissions | 0.000017 | 0.000000 |   0.000000 |            0 |             0 |

| Opening tables       | 0.000043 | 0.000000 |   0.000000 |            0 |             0 |

| System lock          | 0.000023 | 0.000000 |   0.000000 |            0 |             0 |

| init                 | 0.000038 | 0.000000 |   0.000000 |            0 |             0 |

| optimizing           | 0.000010 | 0.000000 |   0.000000 |            0 |             0 |

| statistics           | 0.000024 | 0.000000 |   0.000000 |            0 |             0 |

| preparing            | 0.000018 | 0.000000 |   0.000000 |            0 |             0 |

| executing            | 0.000015 | 0.000000 |   0.000000 |            0 |             0 |

| Sending data         | 0.445040 | 0.428935 |   0.015998 |            0 |             0 |

| end                  | 0.000023 | 0.000000 |   0.000000 |            0 |             0 |

| query end            | 0.000013 | 0.000000 |   0.000000 |            0 |             0 |

| closing tables       | 0.000028 | 0.000000 |   0.000000 |            0 |             0 |

| freeing items        | 0.000041 | 0.000000 |   0.000000 |            0 |             0 |

| logging slow query   | 0.000003 | 0.000000 |   0.000000 |            0 |             0 |

| logging slow query   | 0.000133 | 0.000000 |   0.001000 |            0 |             8 |

| cleaning up          | 0.000008 | 0.000000 |   0.000000 |            0 |             0 |

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

mysql> alter table sbtest change pad pad varchar(120);

Query OK, 1000000 rows affected (14.56 sec)

Records: 1000000  Duplicates: 0  Warnings: 0

mysql> show index from sbtest;

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

| Table  | Non_unique | Key_name | Seq_in_index | Column_name | Collation | Cardinality | Sub_part | Packed | Null | Index_type | Comment | Index_comment |

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

| sbtest |          0 | PRIMARY  |            1 | id          | A         |     1000117 |     NULL | NULL   |      | BTREE      |         |               |

| sbtest |          1 | k        |            1 | k           | A         |           6 |     NULL | NULL   |      | BTREE      |         |               |

| sbtest |          1 | pad      |            1 | pad         | A         |          24 |     NULL | NULL   | YES  | BTREE      |         |               |

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

这里开始有区别了.Cardinality 从200降到24 

varchar(120) Cardinality =200

mysql> desc select count(*) from sbtest order by pad;

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

| id | select_type | table  | type  | possible_keys | key  | key_len | ref  | rows    | Extra       |

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

|  1 | SIMPLE      | sbtest | index | NULL          | pad  | 363     | NULL | 1000117 | Using index |

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

mysql> select count(*) from sbtest order by pad;

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

| count(*) |

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

|  1000000 |

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

1 row in set (0.45 sec)

mysql> show profile cpu,block io for query 8;

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

| Status               | Duration | CPU_user | CPU_system | Block_ops_in | Block_ops_out |

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

| starting             | 0.000120 | 0.000000 |   0.000000 |            0 |             0 |

| checking permissions | 0.000017 | 0.000000 |   0.000000 |            0 |             0 |

| Opening tables       | 0.000046 | 0.000000 |   0.000000 |            0 |             0 |

| System lock          | 0.000028 | 0.000000 |   0.000000 |            0 |             0 |

| init                 | 0.000038 | 0.000000 |   0.000000 |            0 |             0 |

| optimizing           | 0.000011 | 0.000000 |   0.000000 |            0 |             0 |

| statistics           | 0.000023 | 0.000000 |   0.000000 |            0 |             0 |

| preparing            | 0.000018 | 0.000000 |   0.000000 |            0 |             0 |

| executing            | 0.000013 | 0.000000 |   0.000000 |            0 |             0 |

| Sending data         | 0.452434 | 0.437933 |   0.014998 |            0 |             0 |

| end                  | 0.000025 | 0.000000 |   0.000000 |            0 |             0 |

| query end            | 0.000010 | 0.000000 |   0.000000 |            0 |             0 |

| closing tables       | 0.000023 | 0.000000 |   0.000000 |            0 |             0 |

| freeing items        | 0.000033 | 0.000000 |   0.000000 |            0 |             0 |

| logging slow query   | 0.000003 | 0.000000 |   0.000000 |            0 |             0 |

| logging slow query   | 0.000098 | 0.000000 |   0.000000 |            0 |             8 |

| cleaning up          | 0.000007 | 0.000000 |   0.000000 |            0 |             0 |

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

这里也有区别了.有索引的情况下,

是0.44 pk 0.45s

=====================================================================================================

加到varchar(600)试下

mysql> alter table sbtest change pad pad varchar(600);

Query OK, 1000000 rows affected, 2 warnings (14.60 sec)

Records: 1000000  Duplicates: 0  Warnings: 2

mysql> desc select count(*) from sbtest order by pad;

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

| id | select_type | table  | type | possible_keys | key  | key_len | ref  | rows    | Extra |

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

|  1 | SIMPLE      | sbtest | ALL  | NULL          | NULL | NULL    | NULL | 1000117 |       |

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

1 row in set (0.01 sec)

mysql> select count(*) from sbtest order by pad;

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

| count(*) |

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

|  1000000 |

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

1 row in set (0.50 sec)

600是0.5s....