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今日推荐开源项目：《编辑器之神——Vim》

推荐理由：尽管多年过去了，Vim 仍然是热度不减的超级流行开源项目，号称编辑器之神。Vim 是从 vi 发展出来的一个文本编辑器。它类似于vi但又存在区别，因为它功能强大且高度可配置，在vi的基础上进行了很多的改进。代码补全、编译及错误跳转等方便编程的功能特别丰富，在程序员中被广泛使用，还可以创建和更改任何类型的文本，效率非常高。

而从 vi 发展出来的 Vim 具有很多模式，这种独特的设计容易使初学者产生混淆。

Vim 具有6中基本模式和5中派生模式

基本模式

普通模式

在普通模式中，用的编辑器命令，比如移动光标，删除文本等等。这也是Vim 启动后的默认模式。Vim 强大的编辑能力来自于其普通模式命令。普通模式命令往往需要一个操作符结尾。例如普通模式命令”dd”删除当前行，但是第一个”d”的后面可以跟另外的移动命令来代替第二个”d”，比如用移动到下一行的”j”键就可以删除当前行和下一行。另外还可以指定命令重复次数，”2dd”（重复”dd”两次），和”dj”的效果是一样的。在普通模式中，有很多方法可以进入插入模式。比较普通的方式是按”a”（append／追加）键或者”i”（insert／插入）键。

插入模式

在这个模式中，大多数按键都会向文本缓冲区中插入文本。大多数新用户希望文本编辑器编辑过程中一直保持这个模式。在插入模式中，可以按ESC 键回到普通模式。

可视模式

这个模式与普通模式比较相似。但是移动命令会扩大高亮的文本区域。高亮区域可以是字符、行或者是一块文本。当执行一个非移动命令时，命令会被执行到这块高亮的区域上。Vim 的”文本对象”也能和移动命令一样用在这个模式中。

选择模式

这个模式和无模式编辑器的行为比较相似。这个模式中，可以用鼠标或者光标键高亮选择文本，不过输入任何字符的话，Vim 会用这个字符替换选择的高亮文本块，并且自动进入插入模式。

命令行模式

在命令行模式中可以输入会被解释成并执行的文本。例如执行命令（”:”键），搜索（”/”和”?”键）或者过滤命令（”!”键）。在命令执行之后，Vim 返回到命令行模式之前的模式，通常是普通模式。

Ex模式

这和命令行模式比较相似，在使用”:visual”命令离开 Ex 模式前，可以一次执行多条命令。

派生模式

操作符等待模式

这个派生模式指普通模式中，执行一个操作命令后 Vim 等待一个”动作”来完成这个命令。Vim 也支持在操作符等待模式中使用”文本对象”作为动作，包括”aw”一个单词（a word）、”as”一个句子（a sentence）、”ap”一个段落（a paragraph）等等。比如，在普通模式下”d2as”删除当前和下一个句子。在可视模式下”apU”把当前段落所有字母大写。

插入普通模式

这个模式是在插入模式下按下 ctrl+o 键的时候进入。这个时候暂时进入普通模式，执行完一个命令之后，Vim 返回插入模式

插入可视模式

这个模式是在插入模式下按下 ctrl+o 键并且开始一个可视选择的时候开始。在可视区域选择取消的时候，Vim 返回插入模式。

插入选择模式

通常这个模式由插入模式下鼠标拖拽或者 shift 方向键来进入。当选择区域取消的时候，Vim返回插入模式。

替换模式

这是一个特殊的插入模式，在这个模式中可以做和插入模式一样的操作，但是每个输入的字符都会覆盖文本缓冲中已经存在的字符。在普通模式下按”R”键进入。

其他

Evim (Easy Vim)

Evim（Easy Vim）是一个特殊的GUI模式用来尽量的表现的和”无模式”编辑器一样。编辑器自动进入并且停留在插入模式，用户只能通过菜单、鼠标和键盘控制键来对文本进行操作。可以在命令行下输入”evim”或者”vim -y”进入。在 Windows 下，通常也可以点击桌面上 Evim（Easy Vim）的图标。

Vim 的正确学习方式

在正式接触到 Vim 之前，你一定从别人那里听说过 Vim 是多么多么的强无敌，虽然它的命令的确非常方便，但是要正确的入门却不是一件容易的事。一不小心就会弄成《Vim——从入门到放弃》。

要学习这个工具，首先得明白以下几点：

1，学习Vim在开始是痛苦的

2，不要希望你3天就能精通，实际上你可能需要2周甚至更久。

3，需要不断的练习。

学习顺序：

1，在 Insert/Normal 模式下编辑文档（五个命令：i，x，：wq，dd，p）

2，学习更多的命令（插入模式，移动光标，拷贝/粘贴，Undo/Redo，打开/保存/退出/改变文件）

3，学习技巧型命令（如何更好，更快，更强）

4，学习超能力（超能力级功能）

Vim的常用命令

Vim中的命令数不胜数，它可以让你只需要看你的键盘就可以完成所有的事情，但是其中并不是所有的命令都那么常用，这里就列举那些最有用的命令。

这些命令也可以分为以下四级

1，在 Insert/Normal 模式下编辑文档（五个命令：i，x，：wq，dd，p）

2，学习更多的命令（插入模式，移动光标，拷贝/粘贴，Undo/Redo，打开/保存/退出/改变文件）

3，学习技巧型命令（如何更好，更快，更强）

4，学习超能力（杀手级功能）

在 Insert/Normal 模式下编辑文档

打开vim之后默认是Normal模式。Normal模式下你可以操作你的光标，接下来是Normal模式中的一些简单命令，在Normal模式下，几乎所有的键都是功能键。

i —— 插入模式，这个模式让你你可以像记事本一样的输入文本，如果已经输入完了，按ESC返回Normal模式。

x —— 删除当前光标所在处的字符

:w —— 存盘

:q —— 退出，你可以使用 :wq来同时进行这两个操作

dd —— 剪切当前行

p —— 粘贴

hjkl —— 效果等同于←↓↑→，用于移动光标

:help<command> —— 显示相关命令的帮助

学习更多的命令

除了i之外，还有别的插入模式可以选择

a —— 在光标后插入

o —— 在当前行后插入新行

O —— 在当前行前插入新行

一些快速移动光标的指令

0 —— 数字零，到行头

^ —— 到本行第一个不是空字符的位置

$ —— 到行尾

g_ —— 到行尾最后一个不是空字符的位置

/pa —— 搜索 pa 这个字符串，按n查找下一个

关于文件的指令

:e <path/to/file> —— 打开一个文件

:saveas <path/to/file> —— 另存为

:q! —— 不保存退出 :qa!可以退出所有编辑中的文件

:bn :bp ——当你打开了很多文件，用这个切换到下一个/上一个

其他的指令

u —— 撤销

ctrl+r —— 重做

学习技巧型命令

Vim重复自己的方法

. —— 小数点，重复上次命令

N<command> —— 重复一个命令N次

下面是一个特殊的例子

100imeow[ESC] —— 写下100个“meow”

. —— 重复上一个命令也就是再写100个“meow”

3. —— 重复3次命令写下3个（而不是300个）“meow”

进阶级移动光标的命令

NG —— 移动到第N行，:N也可以

gg —— 到第一行

g —— 到最后一行

w —— 到下一个单词开头

e —— 到下一个单词结尾

% —— 当光标在括号上时，可以移动到与之对应的另一个括号

*和# —— 移动到下一个/上一个光标所在的单词上

实际上这些命令都可以组合输入，格式为：<start position><command><end position> 举个简单的例子

0y$ —— 0和 $ 是位置，y是指令，这个指令的意思就是从行头拷贝到本行最后一个字符。

除了 y，还有不少命令可以这么做，比如

d —— 删除

gU/gu —— 变为大写/小写

v ——可视化选择

学习超能力

更高级的移动光标

Fa/fa —— 移动到上一个/下一个a字符，a可以换成其他字符

T,/t, —— 移动到逗号后/前的那一个字符，逗号可以换成其他字符

3fa ——到第三个a字符处

dt” —— 在遇到”前删除所有内容

区域选择

区域选择的命令格式一般为<action>a<object> 和 <action>i<object>

用一个简单的例子来区别a和i

假如说有这样一个字符串——[123((abcd))]，你的光标在b上

vi)——会选择abcd

va)——会选择(abcd)

v2i)——会选择(abcd)

v2a)——会选择((abcd))

自动补齐

在 insert 模式下输入一个词的开头，然后按ctrl+p或+n，就可以使用自动补齐了

宏

qa——开始录制宏，并把你的操作记录在a

@a—— replay你在a录制的宏

@@—— replay最新的宏

今日推荐英文原文：《Why MariaDB Scores Over MySQL》作者：Anand Nayyar

原文链接：https://opensourceforu.com/2018/04/why-mariadb-scores-over-mysql/

推荐理由：自从 MySQL 落入 Oracle 之手之后，江湖上就掀起了血雨腥风；Oracle 有着强大的法律部门，但是在对待开源上哟组合不太良好的历史，所以很多开源社区的用户和支持者都不太信任 Oracle，后来就有了 MariaDB，处于对开源精神的坚持，很多用户转而使用 MariaDB，事实上除了更符合开源精神，MariaDB 也从性能上超越了 MySQL，这篇文章就是告诉你这件事情的。

Why MariaDB Scores Over MySQL

This article gives readers an insight into MariaDB as well as MySQL. Both are analysed and the differences between them are discussed. There is also a section on why MySQL users should switch to MariaDB.

Today, organisations have a range of database options to choose from—whether commercial or open source. There was a time when most database management systems (DBMSs) were commercial. But now, with a number of open source databases available, industry professionals prefer to use them. In fact, open source databases have gained a significant share of the market today, because users have the freedom to implement these systems as per requirements and get the best out of them.

Open source database systems are available from various vendors like Oracle, Microsoft, Google, Amazon and Rackspace. The history of open source DBMSs is not very old. The first operational open source DBMS was MySQL, which was launched in 1995 and till date, lots of significant improvements have been incorporated in it, which has made it a strong competitor even to commercial database software.

Open source DBMSs are gaining popularity not only because they are feature-rich and low cost, but also due to their operational efficiency. The freedom users enjoy in customising the source code as per individual needs, and with little programming knowledge, is a plus point. Gartner reports that open source DBMSs are growing by 42 per cent each year, and this industry will be worth US$ 8 billion by 2020. About 80 per cent of the users polled for the report use some sort of open source software, including DBMSs. Various commercial vendors like Microsoft and IBM are also offering ‘Express Editions’ of their DBMS software.

The most widely adopted open source DBMSs are MySQL and MariaDB. This article discusses their similarities, differences and relative merits, before going on to suggest why users ought to migrate to MariaDB.

Databases

Databases are specific structures that hold data in the form of tables. The software that enables the flow of data through a table-based structure is called a DBMS. The most widely used DBMS is a relational database management system (RDBMS). A DBMS is a computer software application that interacts with end users, other applications and the database itself to capture data. A general-purpose DBMS allows definition, creation, querying, updation and the administration of databases.

The functions of a database and its data are:

Data definition: Creation, modification and removal of definitions that lay the foundation for data organisation

Data updation: Insertion, modification and deletion of data

Retrieval: Retrieval of data from the entire database by making specific queries

Administration: User creation and modification, data security, performance monitoring, data integrity, concurrency control and data recovery

So, a database system is a combination of a database model, a DBMS and a database.

MySQL

MySQL is an open source, multi-threaded, relational database management system (RDBMS) written in C and C++. MySQL was created by a Swedish company, MySQL AB, founded by David Axmark, Allan Larsson and Micheal ‘Monty’ Widenius, and development started in 1994. The first version was launched on May 23, 1995. MySQL is named after co-founder Monty Widenius’s daughter, My. The name of the MySQL dolphin logo, Sakila, was chosen from a huge list of names suggested by users in a ‘Name the Dolphin’ contest.

MySQL server is suitable for mission-critical, heavy-load production systems as well as for embedding into mass deployed software. It is regarded as a central component of the LAMP stack (Linux, Apache, MySQL and PHP). The MySQL database is available for various operating system platforms like Linux, Windows, MAC, BSD UNIX, etc. Popular websites like Wikipedia, Facebook and YouTube use MySQL.

MySQL is now a trademark owned by Oracle Corporation and/or its affiliates, and is dual licensed. Users can choose to use the software as open source under the GNU licence and even purchase a commercial

licence from Oracle.

MySQL architecture

The MySQL server is based on a tiered architecture and consists of both primary sub-systems and support components that interact with each other to read, parse and execute queries to return the results.

The five types of primary sub-systems of MySQL are:

Query engine
Storage manager
Buffer manager
Transaction manager
Recovery manager

Query engine: This contains three main interrelated components—the syntax parser, the query optimiser and the execution component. The syntax parser decomposes the SQL commands it receives from calling programs in a form that is understood by the MySQL engine. The ‘query optimiser’ streamlines the syntax for use by the execution component and then prepares the most efficient plan for query execution. The execution component interprets the execution plan, based on the information it receives and makes requests to other components to retrieve the records.

The storage manager: This interfaces with the operating system to write data to the disk in the form of user tables, indices and logs as well as internal system data.

The query cache: The MySQL engine uses an extremely efficient result set caching mechanism called query cache, which dramatically enhances the response time for queries that are called upon to retrieve the same data as the previous query.

The buffer manager: This handles all memory management issues between requests for data by the query engine and the storage manager. MySQL makes use of memory to cache result sets that can be returned, and the cache is maintained in the buffer manager.

The transaction manager: This sub-system provides a locking facility to ensure that multiple users access the data in a consistent manner without corrupting or damaging the data.

The recovery manager: This keeps copies of data for the purpose of retrieval in case of any sort of data loss.

The two support components of MySQL are:

Process manager
Function libraries

Process manager: This performs two main functions —managing user connections via modules for network connection management, and synchronisation of tasks and processes via modules for multi-threading, thread locking and performing thread-safe operations.

Function libraries: This contains general-purpose routines like string manipulation, sorting operations and performing OS-specific functions like memory management and file I/O.

Features of MySQL

Relational database management system: MySQL supports all features, which makes it a complete RDBMS system. It supports full SQL as a standardised language for querying and updating data, and to administer the database.
Easy and secure: MySQL is very simple and interactive to use, compared to other DBMS software, and is also highly secure with a solid data security layer providing efficient encryption to data.
Client/server architecture: Its simple client/server architecture helps end users to create a server with connectivity to many clients, in order to communicate with the server for inserting, updating and administrating the database.
Scalable: MySQL can handle high volumes of data without any hiccups—as much as 50 million rows. It can handle up to 8TB of data without any issues.
Cross-platform: It is compatible with almost every operating system, like UNIX, Windows, Linux, MAC OS X, etc.
High-performance, flexible and good productivity: MySQL provides faster, highly reliable, cheap storage solutions and supports a large number of embedded applications. It makes use of triggers, procedures and views to deliver better productivity.

MariaDB

MariaDB is a forked version of MySQL. It was primarily developed due to concerns that arose when MySQL was acquired by Oracle Inc. MariaDB is a general-purpose DBMS engineered with extensible architecture to support a broad set of use cases via pluggable storage engines. It uses different storage engines to support different use cases.

MariaDB is an open source, multi-threaded, relational database management system, released under the GNU Public License (GPL). Its lead developer is Michael Monty Widenius, who is also one of the founders of MySQL AB. Many features contribute to MariaDB’s popularity as a database system. Its speed is one of its most prominent features. MariaDB is also remarkably scalable, and is able to handle tens of thousands of tables and billions of rows of data. It can also manage small amounts of data quickly and smoothly, making it convenient for small businesses or personal projects. Another feature that sets it apart from its predecessors is a focus on security. MariaDB’s built-in functions include those for manipulating and formatting text, business and statistical calculations, recording chronological information, as well as speciality features such as those related to GPS mapping.

MariaDB Server is one of the most popular open source databases in the world. It is available in Debian and Ubuntu, and is now the default database on Arch Linux, Manjaro, openSUSE, Red Hat Enterprise Linux, CentOS, Fedora and SUSE Linux Enterprise. And as one of the most broadly adopted and widely deployed in the world, MariaDB Server receives contributions from companies like Alibaba, Facebook and Google. Recently, Microsoft has also joined hands to support the MariaDB community.

Features of MariaDB

MariaDB is available for use under GPL, LGPL and BSD.
It includes a wide selection of storage engines, including high-performance storage engines, for working with other RDBMS data sources.
It uses a standard and popular querying language.
MariaDB runs on a number of operating systems and supports a wide variety of programming languages.
It offers support for PHP, one of the most popular Web development languages.
It offers Galera cluster technology.
MariaDB also offers many operations and commands unavailable in MySQL, and eliminates/replaces features that impact performance negatively.

Other features include multi-source replication, fusion IO optimisations, table discovery and online alter table.

A comparative analysis of MariaDB and MySQL

MariaDB has a significantly high number of new features, which makes it better in terms of performance and user-orientation. Let’s evaluate both MariaDB and MySQL to determine which one is the better. The choice will ultimately depend on the IT managers and their familiarity with open source databases.

Some significant differences between MySQL and MariaDB

1. Usage of the database: Since 1995, MySQL has been regarded as the most implemented and widely used open source database till date. Many IT giants like Twitter, YouTube, Netflix and PayPal, as well as NASA, the US defence forces and Walmart, make use of this database.

MariaDB, being a more recent arrival, is also taking strong root as back-end software in various IT giant organisations, such as Google, Red Hat, CentOS and Fedora.

2. Structure of the database and the index: MySQL is a pure relational database integrated with an ANSI-standard information schema, and consists of tables, columns, views, procedures, triggers, cursors, etc. The SQL of MySQL is a subset of ANSI SQL 99.

MariaDB, on the other hand, is a fork of MySQL and, hence, has the same database structure and index. This facility makes MariaDB a strong choice for users who want to switch or upgrade their back-end directly without any issues of upgrading the database and data structures.

Everything—from the data, table definitions, structures and APIs—remains identical when upgrading from MySQL to MariaDB.

3. Binaries and implementation: MySQL was developed using C and C++ and is fully compatible to run with almost every operating system like Microsoft Windows, MAC OS X, Linux, FreeBSD, UNIX, NetBSD, Novell Netware and many others.

MariaDB was developed using C, C++, Bash and Perl. It is compatible with various operating systems like Microsoft Windows, Linux, MAC OS X, FreeBSD, Solaris, etc.

4. Replication and clustering: MySQL provides strong replication and clustering through master-master and master-slave replication, and makes use of the Galera Cluster for multi-master clustering.

MariaDB provides almost the same replication and clustering facilities to end users as MySQL in terms of master-master and master-slave replication. It also uses Galera Cluster from version 10.1 onwards.

5. Support for databases: MySQL technical support services are provided round-the-clock via Oracle, and the support team consists of professional developers and engineers who provide various facilities like bug fixes, patches and version releases. Oracle offers MySQL premier support, extended support and sustaining support, depending on what users need.

MariaDB provides strong support to users through the open source community, online forums and even via experts. Round-the-clock support is available for MariaDB via enterprise subscription especially for mission-critical production systems.

6. Security: In terms of security, MySQL provides a strong encryption mechanism for tablespace data. It provides strong security parameters in terms of choosing good passwords, not granting unnecessary privileges to users, and ensures application security by preventing SQL injections and data corruption.

MariaDB has had a significant boost in terms of security features like internal security and password check, PAM and LDAP authentication, Kerberos, user roles, and strong encryption over tablespaces, tables and logs.

7. Extensibility: A database supporting an extensible system can be extended by the user in many different ways like adding new data types, functions, operators, aggregate functions, index methods and procedural languages. MySQL has no support for extensibility.

MariaDB is built on a modern architecture that is extensible at every layer—client, cluster, kernel and storage. This extensibility provides two major advantages. It allows for continual community innovation via plugins, which means that a variety of storage engines, like MariaDB ColumnStore or Facebook’s MyRocks, can be integrated through MariaDB’s extensible architecture. Additionally, it makes it easy for customers to configure MariaDB to support a wide variety of use cases, ranging from OLTP to OLAP.

8. JSON support: MySQL supports a native JSON data type that enables efficient access to data in JSON (JavaScript Object Notation) documents. The JSON data type provides the following advantages over storing JSON-format strings in a string column:

Automatic validation of JSON documents stored in JSON columns. Invalid documents produce an error.
Optimised storage format: JSON documents stored in JSON columns are converted to an internal format that permits quick read access to document elements. When the server later has to read a JSON value stored in this binary format, the value need not be parsed from a text representation. The binary format is structured to enable the server to look up sub-objects or nested values directly by key or array index without reading all values before or after them in the document.

On the other hand, MariaDB Server 10.2 introduces a comprehensive set of 24 functions for reading and writing of JSON documents. In addition, the JSON_VALID function can be used with a check constraint for validation, while functions like JSON_VALUE can be used with dynamic columns to index specific fields.

9. Licensing: MySQL offers its code as open source under the GPL, and provides the option of non-GPL commercial distribution in the form of MySQL Enterprise.

MariaDB can only use the GPL, because its work is derived from the MySQL source code under the terms of that licence.

10. Performance: MariaDB achieves best-in-class performance with numerous innovations that are absent for MySQL. These include thread pool management to maximise processing efficiency and extensive optimisation features such as defragmentation within the InnoDB data store. So, when rows are deleted from an InnoDB table, the free space immediately becomes available to the operating system. There’s no need to copy data from old tables to new ones, and there are no gaps in the tablespace. MariaDB also offers engine-independent table statistics to improve the optimiser’s performance, speeding up query processing and data analysis on the size and structure of the tables.

Without these enhancements, MySQL falls short in terms of performance. Thread utilisation in MySQL is sub-optimal and InnoDB tables become fragmented over time, compromising performance.

MariaDB vs MySQL

The following points highlight the pros and cons of MariaDB.

Pros

MariaDB has been optimised for performance and is much more powerful than MySQL for large data sets. Elegant migration from other database systems to MariaDB is yet another benefit.
Switching from MySQL to MariaDB is relatively easy and is a piece of cake for systems administrators.
MariaDB provides better monitoring through the introduction of micro-second precision and extended user statistics.
MariaDB enhances the KILL command to allow you to kill all queries from a user (KILL USER username) or to kill a query ID (KILL QUERY ID query_id). MariaDB has also switched to Perl-compatible regular expressions (PCRE), which offer more powerful and precise queries than standard MySQL regex support.
MariaDB has applied a number of query optimisations for queries connected with disk access, join operations, sub-queries, derived tables and views, execution control, and even explain statements.
MariaDB is purely open source, instead of the dual-licensing model that MySQL uses. Some plugins that are available only for MySQL Enterprise customers have equivalent open source implementations in MariaDB.
MariaDB supports significantly more engines (SphinxSE, Aria, FederatedX, TokuDB, Spider, ScaleDB, etc) compared to MySQL.
MariaDB offers a cluster database for commercial use, which also enables multi-master replication. Anyone can use it freely and reliance on a MySQL Enterprise system is not required.

Cons

Migration of MariaDB back to MySQL has not been possible since release 5.5.36.
For new releases of MariaDB, the appropriate libraries (for Debian) will not be deployed in time, which will result in a required upgrade to a newer version due to dependencies.
Cluster version of MariaDB is not very stable.

Top reasons to migrate to MariaDB

First and foremost, MariaDB offers more and better storage engines. NoSQL support, provided by Cassandra, allows you to run SQL and NoSQL in a single database system. MariaDB also supports TokuDB, which can handle Big Data for large organisations and corporate users.
MySQL’s usual (and slow) database engines MyISAM and InnoDB have been replaced in MariaDB by Aria and XtraDB respectively. Aria offers better caching, which makes a difference when it comes to disk-intensive operations.
MariaDB provides better monitoring through the introduction of micro-second precision and extended user statistics.
The cutting-edge features of MariaDB like GIS, dynamic column support, etc, make it a better choice.
MariaDB follows good industry standards by releasing security announcements and upgrades at the same time, and handling the pre-release secrecy and post-release transparency in a proper way.