varchar 分享影响记忆 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 | | |
+--------+------------+----------+--------------+-------------+-----------+-------------+----------+--------+------+------------+---------+---------------+
这里開始有差别了.Cardinality 从200降到24
varchar(120) Cardinality =200
varchar(60) Cardinality =40 ... 字段是所有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 |
+----------------------+----------+----------+------------+--------------+---------------+
这里也有差别了.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....
版权声明：本文博主原创文章，博客，未经同意不得转载。
varchar 分享影响记忆 试的更多相关文章
- 鹅厂揭秘——高端大气的App电量測试
怎样评价我们开发出来的应用是耗电还是不耗电,怎样測试?这就是我们今天讨论的主题--电量測试,一个在移动应用中新出现的測试类型. 作者简单介绍 watermark/2/text/aHR0cDovL2Js ...
- 学习使用Jmeter做压力測试(一)--压力測试基本概念
一.性能測试的概念 性能測试是通过自己主动化的測试工具模拟多种正常峰值及异常负载条件来对系统的各项性能指标进行測试.负载測试和压力測试都属于性能測试,两者能够结合进行. 通过负载測试, ...
- Memory loss【记忆缺失】
Memory Loss Losing your ability to think and remember is pretty scary. We know the risk of dementia ...
- MySQL中的CHAR和VARCHAR到底支持多长?
最近在研究MySQL的数据类型,我们知道,选择合适的数据类型和数据长度对MySQL的性能影响是不可忽视的,小字段意味着可以MySQL可以读取更多的记录,从而加快查询速度. 网上该问题的答案有很多版本, ...
- 学习MySQL我们应该知道哪些东西？
随笔:小编由于年前一直在找工作,而年后找到工作后又一直在忙工作,所以也很少有时间给大家写点什么,总的来说呢,回顾一下之前面试的几次经历,也曾小小的总结了一下自己的不足,发现自己虽然一直在原有的公司(外 ...
- [No0000CA]什么是“普瑞马法则”？以及 如何利用“普瑞马法则”，三步克服惰性
一般在学习和生活中,我们都可能有这样的经验,就是当说想要作某件事情的时候,但过了好久发现还是没有做:或者觉得有力气使不出来:或者总觉得生活是灰色和抑郁的等等. 这类情况反映在生活中,就是生活好像总是被 ...
- ffmpeg编译选项汇总
编译禁用“jack” 和 “crystalhd” : --disable-crystalhd--disable-indev=jack ================================= ...
- 如何部署 H5 游戏到云服务器？
在自学游戏开发的路上,最有成就感的时刻就是将自己的小游戏做出来分享给朋友试玩,原生的游戏开可以打包分享,小游戏上线流程又长,那 H5 小游戏该怎么分享呢?本文就带大家通过 nginx 将构建好的 H5 ...
- 监控SQL：执行表中所有sql语句、记录每个语句运行时间(3)
原文:监控SQL:执行表中所有sql语句.记录每个语句运行时间(3) 通过执行一个 带参数的存储过程 exec OpreateTB('OpreateUser','IsRun') 更新表的数据 表 ...
随机推荐
- FZU 1894 (双端队列)
Problem 1894 志愿者选拔 Accept: 1166 Submit: 3683 Time Limit: 1500 mSec Memory Limit : 32768 KB Pr ...
- 每日一帖示例程序（使用TWebBrowser基于HTML做）
最近在程序中增加了每日一帖的功能,搜索一下网站的程序,发现大部分是用Memo实现,而我用的是TWebBrowser基于HTML做,故帖出来共享一下. PAS源码: unit Unit1; interf ...
- 如何在SAS中重新构建限价指令簿（Limit Order Book）：使用HashTable
在之前的一篇日志里(http://blog.csdn.net/u010501526/article/details/8875446),我将重新构建LOB(Limit Order Book)分为了三步 ...
- 深入探讨MFC消息循环和消息泵
首先,应该清楚MFC的消息循环(::GetMessage,::PeekMessage),消息泵(CWinThread::PumpMessage)和MFC的消息在窗口之间的路由是两件不同的事情.在MFC ...
- Xtrabackup使用指南 | 简单.生活
Xtrabackup使用指南 | 简单.生活 Xtrabackup是一个对InnoDB做数据备份的工具,支持在线热备份(备份时不影响数据读写),是商业备份工具InnoDB Hotbackup的一个很好 ...
- 马航MH17事件将把普京逼入绝境?
据7月22日报道,马克兰东部民间武装22日凌晨将失事客机的"黑匣子"交给马来西亚方面.乌政府与民间武装允许在坠机地点附的小范围停火. 与此同一时候,联合国安理会21日通过决议,敦促 ...
- 原型链（__proto__）
前面详细的解释了new的几个步骤,其中随意带过了一下原型链的概念,如果细读那篇文章,基本对原型也能有所理解. 原型有两个关键属性,一个是 __proto__ 一个是 prototype ,了解了这两个 ...
- crm2011js操作IFRAME和选项集
- 怎样用Java编写一段代码引发内存泄露
通过下面步骤能够非常easy产生内存泄露(程序代码不能訪问到某些对象,可是它们仍然保存在内存中): 应用程序创建一个长时间执行的线程(或者使用线程池,会更快地发生内存泄露). 线程通过某个类载入器(能 ...
- Lambda高手之路第三部分
转http://www.cnblogs.com/lazycoding/archive/2013/01/06/2847587.html 背后的秘密-MSIL 通过著名的LINQPad,我们可以更深入的查 ...