impdp中的DISABLE_ARCHIVE_LOGGING参数测试

联系:手机/微信(+86 13429648788) QQ(107644445)

标题:impdp中的DISABLE_ARCHIVE_LOGGING参数测试

作者:惜分飞©版权所有[未经本人同意,不得以任何形式转载,否则有进一步追究法律责任的权利.]

在oracle 12c版本中引入了impdp中的TRANSFORM中的DISABLE_ARCHIVE_LOGGING值,可以实现在导入的时候使用nologging处理从而减少日志量也增加速度,但是在force logging情况下该参数无效
创建测试表

[oracle@localhost ~]$ sqlplus xff/oracle@localhost/pdb
 
SQL*Plus: Release 12.2.0.1.0 Production on Fri Apr 7 10:20:45 2017
 
Copyright (c) 1982, 2016, Oracle.  All rights reserved.
 
 
Connected to:
Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit Production
 
SQL> create table t_xifenfei as select * from dba_objects;
 
Table created.
 
SQL> insert into t_xifenfei select * from t_xifenfei;
 
217838 rows created.
 
SQL> /
 
435676 rows created.
 
SQL> /
 
871352 rows created.
 
SQL> /
 
1742704 rows created.
 
SQL> commit;
 
Commit complete.
 
SQL> select count(*) from t_xifenfei;
 
  COUNT(*)
----------
   3485408

导出测试表

[oracle@localhost ~]$ expdp xff/oracle@localhost/pdb dumpfile=t_xifenfei.dmp tables=t_xifenfei REUSE_DUMPFILES=yes
 
Export: Release 12.2.0.1.0 - Production on Fri Apr 7 11:55:01 2017
 
Copyright (c) 1982, 2017, Oracle and/or its affiliates.  All rights reserved.
 
Connected to: Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit Production
Starting "XFF"."SYS_EXPORT_TABLE_01":  xff/********@localhost/pdb dumpfile=t_xifenfei.dmp tables=t_xifenfei REUSE_DUMPFILES=yes
Processing object type TABLE_EXPORT/TABLE/TABLE_DATA
Processing object type TABLE_EXPORT/TABLE/STATISTICS/TABLE_STATISTICS
Processing object type TABLE_EXPORT/TABLE/STATISTICS/MARKER
Processing object type TABLE_EXPORT/TABLE/TABLE
. . exported "XFF"."T_XIFENFEI"                          460.6 MB 3485408 rows
Master table "XFF"."SYS_EXPORT_TABLE_01" successfully loaded/unloaded
******************************************************************************
Dump file set for XFF.SYS_EXPORT_TABLE_01 is:
  /u01/app/oracle/admin/xffdb/dpdump/4A93528C587D82CEE055000000000001/t_xifenfei.dmp
Job "XFF"."SYS_EXPORT_TABLE_01" successfully completed at Fri Apr 7 11:55:59 2017 elapsed 0 00:00:58

归档模式下不使用DISABLE_ARCHIVE_LOGGING导入

[oracle@localhost rdbms]$ sqlplus / as sysdba
 
SQL*Plus: Release 12.2.0.1.0 Production on Sat Apr 8 02:43:23 2017
 
Copyright (c) 1982, 2016, Oracle.  All rights reserved.
 
 
Connected to:
Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit Production
 
SQL> select force_logging from v$database;
 
FORCE_LOGGING
---------------------------------------
NO
 
SQL> alter system switch logfile;
 
System altered.
 
SQL> archive log list;
Database log mode              Archive Mode
Automatic archival             Enabled
Archive destination            USE_DB_RECOVERY_FILE_DEST
Oldest online log sequence     14
Next log sequence to archive   16
Current log sequence           16
 
[oracle@localhost ~]$  impdp xff/oracle@localhost/pdb dumpfile=t_xifenfei.dmp
 
Import: Release 12.2.0.1.0 - Production on Sat Apr 8 02:46:05 2017
 
Copyright (c) 1982, 2017, Oracle and/or its affiliates.  All rights reserved.
 
Connected to: Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit Production
Master table "XFF"."SYS_IMPORT_FULL_01" successfully loaded/unloaded
Starting "XFF"."SYS_IMPORT_FULL_01":  xff/********@localhost/pdb dumpfile=t_xifenfei.dmp
Processing object type TABLE_EXPORT/TABLE/TABLE
Processing object type TABLE_EXPORT/TABLE/TABLE_DATA
. . imported "XFF"."T_XIFENFEI"                          460.6 MB 3485408 rows
Processing object type TABLE_EXPORT/TABLE/STATISTICS/TABLE_STATISTICS
Processing object type TABLE_EXPORT/TABLE/STATISTICS/MARKER
Job "XFF"."SYS_IMPORT_FULL_01" successfully completed at Sat Apr 8 02:47:08 2017 elapsed 0 00:01:02
 
[oracle@localhost ~]$ sqlplus / as sysdba
 
SQL*Plus: Release 12.2.0.1.0 Production on Sat Apr 8 02:47:30 2017
 
Copyright (c) 1982, 2016, Oracle.  All rights reserved.
 
 
Connected to:
Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit Production
 
SQL> archive log list;
Database log mode              Archive Mode
Automatic archival             Enabled
Archive destination            USE_DB_RECOVERY_FILE_DEST
Oldest online log sequence     17
Next log sequence to archive   19
Current log sequence           19

这里可以看出来,导入过程使用时间为1分钟多,导入过程日志切换 了3次

归档模式下使用DISABLE_ARCHIVE_LOGGING导入

[oracle@localhost ~]$ sqlplus xff/oracle@localhost/pdb
 
SQL*Plus: Release 12.2.0.1.0 Production on Sat Apr 8 02:49:23 2017
 
Copyright (c) 1982, 2016, Oracle.  All rights reserved.
 
Last Successful login time: Sat Apr 08 2017 02:46:05 -04:00
 
Connected to:
Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit Production
 
SQL> drop table t_xifenfei purge;
 
Table dropped.
SQL> exit
Disconnected from Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit Production
[oracle@localhost ~]$ sqlplus / as sysdba
 
SQL*Plus: Release 12.2.0.1.0 Production on Sat Apr 8 02:50:00 2017
 
Copyright (c) 1982, 2016, Oracle.  All rights reserved.
 
 
Connected to:
Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit Production
 
SQL> alter system switch logfile;
 
System altered.
 
SQL> archive log list;
Database log mode              Archive Mode
Automatic archival             Enabled
Archive destination            USE_DB_RECOVERY_FILE_DEST
Oldest online log sequence     18
Next log sequence to archive   20
Current log sequence           20
 
 
[oracle@localhost ~]$  impdp xff/oracle@localhost/pdb dumpfile=t_xifenfei.dmp TRANSFORM=DISABLE_ARCHIVE_LOGGING:y
 
Import: Release 12.2.0.1.0 - Production on Sat Apr 8 02:54:49 2017
 
Copyright (c) 1982, 2017, Oracle and/or its affiliates.  All rights reserved.
 
Connected to: Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit Production
Master table "XFF"."SYS_IMPORT_FULL_01" successfully loaded/unloaded
Starting "XFF"."SYS_IMPORT_FULL_01":  xff/********@localhost/pdb dumpfile=t_xifenfei.dmp TRANSFORM=DISABLE_ARCHIVE_LOGGING:y
Processing object type TABLE_EXPORT/TABLE/TABLE
Processing object type TABLE_EXPORT/TABLE/TABLE_DATA
. . imported "XFF"."T_XIFENFEI"                          460.6 MB 3485408 rows
Processing object type TABLE_EXPORT/TABLE/STATISTICS/TABLE_STATISTICS
Processing object type TABLE_EXPORT/TABLE/STATISTICS/MARKER
Job "XFF"."SYS_IMPORT_FULL_01" successfully completed at Sat Apr 8 02:55:00 2017 elapsed 0 00:00:10
[oracle@localhost ~]$ sqlplus / as sysdba
 
SQL*Plus: Release 12.2.0.1.0 Production on Sat Apr 8 02:55:45 2017
 
Copyright (c) 1982, 2016, Oracle.  All rights reserved.
 
 
Connected to:
Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit Production
 
SQL> archive log list;
Database log mode              Archive Mode
Automatic archival             Enabled
Archive destination            USE_DB_RECOVERY_FILE_DEST
Oldest online log sequence     18
Next log sequence to archive   20
Current log sequence           20

这里可以看出来当使用了DISABLE_ARCHIVE_LOGGING为Y之后导入日志没有发生切换,导入时间仅为10s.

非归档模式下不使用DISABLE_ARCHIVE_LOGGING导入

SQL> alter system switch logfile;
 
System altered.
 
SQL> archive log list;
Database log mode              No Archive Mode
Automatic archival             Disabled
Archive destination            USE_DB_RECOVERY_FILE_DEST
Oldest online log sequence     19
Current log sequence           21
SQL> drop table xff.t_xifenfei purge;
 
Table dropped.
 
[oracle@localhost ~]$  impdp xff/oracle@localhost/pdb dumpfile=t_xifenfei.dmp
 
Import: Release 12.2.0.1.0 - Production on Sat Apr 8 03:22:42 2017
 
Copyright (c) 1982, 2017, Oracle and/or its affiliates.  All rights reserved.
 
Connected to: Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit Production
Master table "XFF"."SYS_IMPORT_FULL_01" successfully loaded/unloaded
Starting "XFF"."SYS_IMPORT_FULL_01":  xff/********@localhost/pdb dumpfile=t_xifenfei.dmp
Processing object type TABLE_EXPORT/TABLE/TABLE
Processing object type TABLE_EXPORT/TABLE/TABLE_DATA
. . imported "XFF"."T_XIFENFEI"                          460.6 MB 3485408 rows
Processing object type TABLE_EXPORT/TABLE/STATISTICS/TABLE_STATISTICS
Processing object type TABLE_EXPORT/TABLE/STATISTICS/MARKER
Job "XFF"."SYS_IMPORT_FULL_01" successfully completed at Sat Apr 8 03:23:17 2017 elapsed 0 00:00:27
 
[oracle@localhost ~]$ sqlplus / as sysdba
 
SQL*Plus: Release 12.2.0.1.0 Production on Sat Apr 8 03:23:49 2017
 
Copyright (c) 1982, 2016, Oracle.  All rights reserved.
 
 
Connected to:
Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit Production
 
SQL> archive log list;
Database log mode              No Archive Mode
Automatic archival             Disabled
Archive destination            USE_DB_RECOVERY_FILE_DEST
Oldest online log sequence     19
Current log sequence           21

这里测试在非归档模式下不设置DISABLE_ARCHIVE_LOGGING,日志量增加不明显,导入时间变为为27秒.

非归档模式下使用DISABLE_ARCHIVE_LOGGING导入

[oracle@localhost ~]$ sqlplus xff/oracle@localhost/pdb
 
SQL*Plus: Release 12.2.0.1.0 Production on Sat Apr 8 03:24:10 2017
 
Copyright (c) 1982, 2016, Oracle.  All rights reserved.
 
Last Successful login time: Sat Apr 08 2017 03:22:43 -04:00
 
Connected to:
Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit Production
 
SQL> drop table t_xifenfei purge;
 
Table dropped.
 
SQL> conn / as sysdba
Connected.
SQL> alter system switch logfile;
 
System altered.
 
SQL> archive log list;
Database log mode              No Archive Mode
Automatic archival             Disabled
Archive destination            USE_DB_RECOVERY_FILE_DEST
Oldest online log sequence     20
Current log sequence           22
 
[oracle@localhost ~]$  impdp xff/oracle@localhost/pdb dumpfile=t_xifenfei.dmp TRANSFORM=DISABLE_ARCHIVE_LOGGING:y
 
Import: Release 12.2.0.1.0 - Production on Sat Apr 8 03:25:51 2017
 
Copyright (c) 1982, 2017, Oracle and/or its affiliates.  All rights reserved.
 
Connected to: Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit Production
Master table "XFF"."SYS_IMPORT_FULL_01" successfully loaded/unloaded
Starting "XFF"."SYS_IMPORT_FULL_01":  xff/********@localhost/pdb dumpfile=t_xifenfei.dmp TRANSFORM=DISABLE_ARCHIVE_LOGGING:y
Processing object type TABLE_EXPORT/TABLE/TABLE
Processing object type TABLE_EXPORT/TABLE/TABLE_DATA
. . imported "XFF"."T_XIFENFEI"                          460.6 MB 3485408 rows
Processing object type TABLE_EXPORT/TABLE/STATISTICS/TABLE_STATISTICS
Processing object type TABLE_EXPORT/TABLE/STATISTICS/MARKER
Job "XFF"."SYS_IMPORT_FULL_01" successfully completed at Sat Apr 8 03:26:01 2017 elapsed 0 00:00:10
[oracle@localhost ~]$ sqlplus / as sysdba
 
SQL*Plus: Release 12.2.0.1.0 Production on Sat Apr 8 03:26:37 2017
 
Copyright (c) 1982, 2016, Oracle.  All rights reserved.
 
 
Connected to:
Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit Production
 
SQL> archive log list;
Database log mode              No Archive Mode
Automatic archival             Disabled
Archive destination            USE_DB_RECOVERY_FILE_DEST
Oldest online log sequence     20
Current log sequence           22

这里可以看出来在非归档模式下使用DISABLE_ARCHIVE_LOGGING导入时间为10s,日志量也没有明显增加。

在force logging在非归档情况下使用不DISABLE_ARCHIVE_LOGGING参数

[oracle@localhost ~]$ sqlplus xff/oracle@localhost/pdb
 
SQL*Plus: Release 12.2.0.1.0 Production on Sat Apr 8 10:07:07 2017
 
Copyright (c) 1982, 2016, Oracle.  All rights reserved.
 
Last Successful login time: Sat Apr 08 2017 03:29:36 -04:00
 
Connected to:
Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit Production
 
SQL> drop table t_xifenfei purge;
 
Table dropped.
SQL> alter system switch logfile;
 
System altered.
 
SQL> archive log list;
Database log mode              No Archive Mode
Automatic archival             Disabled
Archive destination            USE_DB_RECOVERY_FILE_DEST
Oldest online log sequence     22
Current log sequence           24
SQL> select force_logging from v$database;
 
FORCE_LOGGING
---------------------------------------
YES
 
[oracle@localhost ~]$ impdp xff/oracle@localhost/pdb dumpfile=t_xifenfei.dmp TRANSFORM=DISABLE_ARCHIVE_LOGGING:y
 
Import: Release 12.2.0.1.0 - Production on Sat Apr 8 10:10:39 2017
 
Copyright (c) 1982, 2017, Oracle and/or its affiliates.  All rights reserved.
 
Connected to: Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit Production
Master table "XFF"."SYS_IMPORT_FULL_01" successfully loaded/unloaded
Starting "XFF"."SYS_IMPORT_FULL_01":  xff/********@localhost/pdb dumpfile=t_xifenfei.dmp TRANSFORM=DISABLE_ARCHIVE_LOGGING:y
Processing object type TABLE_EXPORT/TABLE/TABLE
Processing object type TABLE_EXPORT/TABLE/TABLE_DATA
. . imported "XFF"."T_XIFENFEI"                          460.6 MB 3485408 rows
Processing object type TABLE_EXPORT/TABLE/STATISTICS/TABLE_STATISTICS
Processing object type TABLE_EXPORT/TABLE/STATISTICS/MARKER
Job "XFF"."SYS_IMPORT_FULL_01" successfully completed at Sat Apr 8 10:11:02 2017 elapsed 0 00:00:21
 
[oracle@localhost ~]$ sqlplus / as sysdba
 
SQL*Plus: Release 12.2.0.1.0 Production on Sat Apr 8 10:11:17 2017
 
Copyright (c) 1982, 2016, Oracle.  All rights reserved.
 
 
Connected to:
Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit Production
 
SQL> archive log lsit;
SP2-0718: illegal ARCHIVE LOG option
SQL> archive log list;
Database log mode              No Archive Mode
Automatic archival             Disabled
Archive destination            USE_DB_RECOVERY_FILE_DEST
Oldest online log sequence     22
Current log sequence           24

这可以可以看出来在非归档情况下force logging无明显增加日志量和导入时间

在force logging在归档情况下使用DISABLE_ARCHIVE_LOGGING参数

SQL> drop table xff.t_xifenfei purge;
 
Table dropped.
 
SQL> alter system switch logfile;
 
System altered.
 
SQL> select force_logging from v$database;
 
FORCE_LOGGING
---------------------------------------
YES
 
SQL> archive log list;
Database log mode              Archive Mode
Automatic archival             Enabled
Archive destination            USE_DB_RECOVERY_FILE_DEST
Oldest online log sequence     23
Next log sequence to archive   25
Current log sequence           25
 
[oracle@localhost ~]$ impdp xff/oracle@localhost/pdb dumpfile=t_xifenfei.dmp TRANSFORM=DISABLE_ARCHIVE_LOGGING:y
 
Import: Release 12.2.0.1.0 - Production on Sat Apr 8 10:33:28 2017
 
Copyright (c) 1982, 2017, Oracle and/or its affiliates.  All rights reserved.
 
Connected to: Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit Production
Master table "XFF"."SYS_IMPORT_FULL_01" successfully loaded/unloaded
Starting "XFF"."SYS_IMPORT_FULL_01":  xff/********@localhost/pdb dumpfile=t_xifenfei.dmp TRANSFORM=DISABLE_ARCHIVE_LOGGING:y
Processing object type TABLE_EXPORT/TABLE/TABLE
Processing object type TABLE_EXPORT/TABLE/TABLE_DATA
. . imported "XFF"."T_XIFENFEI"                          460.6 MB 3485408 rows
Processing object type TABLE_EXPORT/TABLE/STATISTICS/TABLE_STATISTICS
Processing object type TABLE_EXPORT/TABLE/STATISTICS/MARKER
Job "XFF"."SYS_IMPORT_FULL_01" successfully completed at Sat Apr 8 10:34:50 2017 elapsed 0 00:01:15
[oracle@localhost ~]$ sqlplus / as sysdba
 
SQL*Plus: Release 12.2.0.1.0 Production on Sat Apr 8 10:35:09 2017
 
Copyright (c) 1982, 2016, Oracle.  All rights reserved.
 
 
Connected to:
Oracle Database 12c Enterprise Edition Release 12.2.0.1.0 - 64bit Production
 
SQL> archive log list;
Database log mode              Archive Mode
Automatic archival             Enabled
Archive destination            USE_DB_RECOVERY_FILE_DEST
Oldest online log sequence     26
Next log sequence to archive   28
Current log sequence           28

这里可以看出来在force logging情况下,设置DISABLE_ARCHIVE_LOGGING参数不生效
从上述测试在不管是非归档还是归档情况下使用DISABLE_ARCHIVE_LOGGING都会减小导入时间,减少归档量,但是需要注意如果数据库是force logging情况下,DISABLE_ARCHIVE_LOGGING参数会无效。

impdp中的DISABLE_ARCHIVE_LOGGING参数测试的更多相关文章

  1. expdp impdp中 exclude/include 的使用

    exclude和include参数能够在使用expdp或impdp是对特定的对象或对象类型进行筛选或过滤.比如因工作的需要导出特定的表或不导出特定 的表.视图以及存储过程.索引.约束.授权统计信息等等 ...

  2. 转://oracle Wallet在expdp/impdp中使用场景

    oracle Wallet的使用(即内部加密技术TDE(Transparent Data Encryption )) 1. TDE是Oracle10gR2中推出的一个新功能,使用时要保证Oracle版 ...

  3. Oracle expdp impdp中 exclude/include 的使用

    exclude和include参数能够在使用expdp或impdp是对特定的对象或对象类型进行筛选或过滤.比如因工作的需要导出特定的表或不导出特定的表.视图以及存储过程.索引.约束.授权统计信息等等. ...

  4. zzw原创_expdp及impdp中的exclude及include参数的那点事

    zzw原创:转载请注明出处 在oracle的expdp 及imdpd命令中,exclude及include参数还是有一些要注意的地方,特别是涉及选择性条件时. 一.通用 1.exclude及inclu ...

  5. ORA-01578和ORA-26040--NOLOGGING操作引起的坏块-错误解释和解决方案(文档ID 1623284.1)

    ORA-01578和ORA-26040--NOLOGGING操作引起的坏块-错误解释和解决方案(文档ID 1623284.1) (一)NOLOGGING操作引起的坏块(ORA-01578和ORA-26 ...

  6. 使用datapump 导出导入同义词(export and import synonym using datapump)

    对于同义词的备份我们有多种方式来实现,如直接通过脚本生成同义词的创建脚本,或者使用dbms_metadata.get_ddl来提取同义词的定义脚本.然而在使用传统的exp或是datapump expd ...

  7. ORACLE 11G R2 RAC classical install OGG12.1(LINUX) 经典抽取模式单项同步配置OGG12.1

    博文结构图如下: 一.环境描述以及注意事项 1.1 环境简介 IP 系统 Oracle版本 OGG版本 源端 172.16.10.16/36 RHEL6.5 oracle11204 12.1 目标端 ...

  8. Oracle 数据库导入与出

    Oracle 数据库导入与出 导出( EXPORT )是用 EXP 将数据库部分或全对象的结构和导出 . 导入( 导入( IMPORT )是用 )是用 IMP IMP将 OS 文件中的对象结构和数据装 ...

  9. 深入探索 JUnit 4

    开始之前 关于本教程 引入 Java 5 注释为 JUnit 带来了显著改变,使它从一个受广大开发人员了解和喜爱的测试框架转变成了一个更为精简但却不那么为人熟知的框架.在本教程中,我将探讨 JUnit ...

随机推荐

  1. JVM从入门开始深入每一个底层细节

    1 官网 1.1 寻找JDK文档过程 www.oracle.com -> 右下角Product Documentation -> 往下拉选择Java -> Java SE docum ...

  2. 使用npm link 加速调试

    我们在把包发布到npm上时,如果需要对本地的包进行修改,我们需要改变一个版本,重新发布.然后测试时需要更新这个包进行测试.这样的话,每一次的调试都特别麻烦.我们可以使用npm link来加速这个调试过 ...

  3. InfluxDB因修改默认数据目录导致服务无法正常运行的问题(权限问题)

    在实际的生产中,考虑的实际情况,我们会调整一些默认配置,例如,数据目录.InfluxDB修改默认的Data目录后,因权限问题,服务无法正常运行.以下是具体的分析测试过程. 配置文件为 /etc/inf ...

  4. Scrapy的下载中间件

    下载中间件 简介 下载器,无法执行js代码,本身不支持代理 下载中间件用来hooks进Scrapy的request/response处理过程的框架,一个轻量级的底层系统,用来全局修改scrapy的re ...

  5. Linux:Apache服务器的搭建

    下载安装并启动apache服务 安装apache服务 yum install -y httpd 启动apache服务 systemctl start httpd.service apache服务器的目 ...

  6. crossover mac如何使用?crossover mac使用教程

    CrossOver Mac 破解版可以在 Mac 上运行成千上万的 Windows 程序,从办公软件.实用工具.游戏到设计软件.CrossOver 19 破解版可以让 Windows 程序和 Mac ...

  7. Codeforces Round #598 (Div. 3)

    传送门 A. Payment Without Change 签到. Code /* * Author: heyuhhh * Created Time: 2019/11/4 21:19:19 */ #i ...

  8. LG5337/BZOJ5508 「TJOI2019」甲苯先生的字符串 线性动态规划+矩阵加速

    问题描述 LG5337 BZOJ5508 题解 设\(opt_{i,j}(i \in [1,n],j \in [1,26])\)代表区间\([1,i]\),结尾为\(j\)的写法. 设\(exist_ ...

  9. 使用adb安装apk到手机

    [ADB]Android debug bridge.Android手机实际是基于Linux系统的.通过USB线将android手机与电脑连起来,在电脑上dos命令行中敲adb shell命令,可以登录 ...

  10. OC:浅析Runtime中消息转发机制

    一.介绍 OC是一门动态性语言,其实现的本质是利用runtime机制.在runtime中,对象调用方法,其实就是给对象发送一个消息,也即objc_msgSend().在这个消息发送的过程中,系统会进行 ...