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Online Schema Change for MySQL

Project description

OnlineSchemaChange is a tool for making schema changes for MySQL tables in a non-blocking way


OSC must be run on the same host as MySQL server.

copy mode

Say we have an existing table named my_table under database test:

CREATE TABLE `my_table` (
  `id` int(11) NOT NULL,
  PRIMARY KEY (`id`)

Now if we want to run ALTER TABLE ``my_table add column data varchar(10);`` against it. Instead of feed the ALTER TABLE statement to OSC, we just need to put a CREATE TABLE statement representing the desired schema into a file /tmp/foo.sql like below:

CREATE TABLE `my_table` (
  `id` int(11) NOT NULL,
  `data` varchar(10) DEFAULT NULL,
  PRIMARY KEY (`id`)

Then run the following command:

osc_cli copy --ddl-file-list=foo.sql --socket=/tmp/mysql.socket --database=test

cleanup mode

To cleanup the table left behind by last run of OSC

osc_cli cleanup --socket=/tmp/mysql.socket --database=test

To terminate a currently running OSC process on certain MySQL Instance:

osc_cli cleanup

direct mode

This mode is reserved for utilizing MySQL’s native online ddl for schema change, and help DBA manage all the schema related operation into this one tool. For now, if you plan to use OSC for all your schema management, this mode is here for you to create a empty new table. Following command will create an empty table into database test

osc_cli direct --ddl-file-list=foo.sql --socket=/tmp/mysql.socket --database=test


OnlineSchemaChange requires

System packages

For Python2

sudo apt-get install python-dev libmysqlclient-dev # Debian / Ubuntu
sudo yum install python-devel mysql-devel # Red Hat / CentOS

For Python3

sudo apt-get install python3-dev # debian / Ubuntu
sudo yum install python3-devel # Red Hat / CentOS

Python requirements * python >= 2.7 * python module: six, pyparsing, MySQLdb

Installing OnlineSchemaChange

Run following command to install dependency

python install --install-scripts=/usr/local/bin

If you have multiple python version available in your environment, or you don’t want mess up with system’s default python, you can use pyenv and virtualenv

How OnlineSchemaChange works

Check wiki page for more detail, and some advanced usage.

How to contribute

Check this wiki page if you want to contribute to this project.


OnlineSchemaChange is BSD-licensed. We also provide an additional patent grant.

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