# What is mydumper? Why?

* Parallelism (hence, speed) and performance (avoids expensive character set conversion routines, efficient code overall)
* Easier to manage output (separate files for tables, dump metadata, etc, easy to view/parse data)
* Consistency - maintains snapshot across all threads, provides accurate master and slave log positions, etc
* Manageability - supports PCRE for specifying database and tables inclusions and exclusions

## How to install mydumper/myloader?

First get the correct url from the [releases section](https://github.com/maxbube/mydumper/releases) then:

### RedHat / Centos

```bash
yum install https://github.com/maxbube/mydumper/releases/download/v0.9.5/mydumper-0.9.5-1.el7.x86_64.rpm
```

### Ubuntu / Debian

```bash
wget https://github.com/maxbube/mydumper/releases/download/v0.9.5/mydumper_0.9.5-1.xenial_amd64.deb
dpkg -i mydumper_0.9.5-1.xenial_amd64.deb
```

## How to build it?

Run:

```bash
cmake .
make
```

One needs to install development versions of required libaries (MySQL, GLib, ZLib, PCRE):
NOTE: you must use the correspondent mysql devel package.

* Ubuntu or Debian: apt-get install libglib2.0-dev libmysqlclient15-dev zlib1g-dev libpcre3-dev libssl-dev
* Fedora, RedHat and CentOS: yum install glib2-devel mysql-devel zlib-devel pcre-devel openssl-devel
* openSUSE: zypper install glib2-devel libmysqlclient-devel pcre-devel zlib-devel
* MacOSX: port install glib2 mysql5 pcre pkgconfig cmake
 (You may want to run 'port select mysql mysql5' afterwards)

One has to make sure, that pkg-config, mysql_config, pcre-config are all in $PATH

Binlog dump is disabled by default to compile with it you need to add -DWITH_BINLOG=ON to cmake options

To build against mysql libs < 5.7 you need to disable SSL adding -DWITH_SSL=OFF

## How does consistent snapshot work?

This is all done following best MySQL practices and traditions:

* As a precaution, slow running queries on the server either abort the dump, or get killed
* Global write lock is acquired ("FLUSH TABLES WITH READ LOCK")
* Various metadata is read ("SHOW SLAVE STATUS","SHOW MASTER STATUS")
* Other threads connect and establish snapshots ("START TRANSACTION WITH CONSISTENT SNAPSHOT")
** On pre-4.1.8 it creates dummy InnoDB table, and reads from it.
* Once all worker threads announce the snapshot establishment, master executes "UNLOCK TABLES" and starts queueing jobs.

This for now does not provide consistent snapshots for non-transactional engines - support for that is expected in 0.2 :)

## How to exclude (or include) databases?

Once can use --regex functionality, for example not to dump mysql and test databases:

```bash
 mydumper --regex '^(?!(mysql\.|test\.))'
```

To dump only mysql and test databases:

```bash
 mydumper --regex '^(mysql\.|test\.)'
```

To not dump all databases starting with test:

```bash
 mydumper --regex '^(?!(test))'
```

Of course, regex functionality can be used to describe pretty much any list of tables.