varchar 所占内存的影响 测试，varchar占内存测试
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 |
+----------+
char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 | 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 |
+----------------------------------------------------+
| qqqqqqqqqqwwwwwwwwwweeeeeeeeeerrrrrrrrrrtttttttttt |
| qqqqqqqqqqwwwwwwwwwweeeeeeeeeerrrrrrrrrrtttttttttt |
| qqqqqqqqqqwwwwwwwwwweeeeeeeeeerrrrrrrrrrtttttttttt |
| qqqqqqqqqqwwwwwwwwwweeeeeeeeeerrrrrrrrrrtttttttttt |
| qqqqqqqqqqwwwwwwwwwweeeeeeeeeerrrrrrrrrrtttttttttt |
| qqqqqqqqqqwwwwwwwwwweeeeeeeeeerrrrrrrrrrtttttttttt |
| qqqqqqqqqqwwwwwwwwwweeeeeeeeeerrrrrrrrrrtttttttttt |
| qqqqqqqqqqwwwwwwwwwweeeeeeeeeerrrrrrrrrrtttttttttt |
| qqqqqqqqqqwwwwwwwwwweeeeeeeeeerrrrrrrrrrtttttttttt |
| qqqqqqqqqqwwwwwwwwwweeeeeeeeeerrrrrrrrrrtttttttttt |
| qqqqqqqqqqwwwwwwwwwweeeeeeeeeerrrrrrrrrrtttttttttt |
| qqqqqqqqqqwwwwwwwwwweeeeeeeeeerrrrrrrrrrtttttttttt |
| qqqqqqqqqqwwwwwwwwwweeeeeeeeeerrrrrrrrrrtttttttttt |
| qqqqqqqqqqwwwwwwwwwweeeeeeeeeerrrrrrrrrrtttttttttt |
| qqqqqqqqqqwwwwwwwwwweeeeeeeeeerrrrrrrrrrtttttttttt |
| qqqqqqqqqqwwwwwwwwwweeeeeeeeeerrrrrrrrrrtttttttttt |
| qqqqqqqqqqwwwwwwwwwweeeeeeeeeerrrrrrrrrrtttttttttt |
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：＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝
varchar(60)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 |
+----------------------+----------+----------+------------+--------------+---------------+
varchar(120)的:
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
varchar(60) Cardinality =40 ... 字段是全部60char长度的
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....
这是一个测试的方法，参考网上的，具体可以看提供给你的网址
package com;
public class Sizeof {
public static void main(String[] args) throws Exception {
// Warm up all classes/methods we will use
runGC();
usedMemory();
// Array to keep strong references to allocated objects
final int count = 100000;
Object[] objects = new Object[count];
long heap1 = 0;
// Allocate count+1 objects, discard the first one
for (int i = -1; i < count; ++i) {
Object object = null;
// Instantiate your data here and assign it to object
object = new Object();
// object = new Integer (i);
// object = new Long (i);
// object = new String ();
// object = new byte [128][1]
if (i >= 0)
objects[i] = object;
else {
object = null; // Discard the warm up object
runGC();
heap1 = usedMemory(); // Take a before heap snapshot
}
}
runGC();
long heap2 = usedMemory(); // Take an after heap snapshot:
final int size = Math.round(((float) (heap2 - heap1)) / count);
System.out.println("'before' heap: " + heap1 + ", 'after' heap: "
+ heap2);
System.out.println("heap delta: " + (heap2 - heap1) + ", {"
+ objects[0].getClass() + "} size = " + size + " bytes");
for (int i = 0; i < count; ++i)
objects[i] = null;
objects = null;
}
private static void runGC() throws Exception {
&......余下全文>>
要看你的编码格式，utf-8占三字节，gb2312占二字节
比如你的格式是utf-8
那么varchar(1)的长度就是占用三字节。可以存一个汉字或字母，而这个汉字或字母就是占了三个字节