gh-ost

GitHub's online schema migration for MySQL

gh-ost allows for online schema migrations in MySQL which are:

Triggerless
Testable
Pausable
Operations-friendly

How?

WORK IN PROGRESS

Please meanwhile refer to the docs for more information. No, really, go to the docs.

Usage

Testing on replica

gh-ost --conf=.my.cnf --database=mydb --table=mytable --verbose --alter="engine=innodb" --execute --initially-drop-ghost-table --initially-drop-old-table -max-load=Threads_connected=30 --switch-to-rbr --chunk-size=2500 --cut-over=two-step --exact-rowcount --test-on-replica --verbose

Please read more on testing on replica

Executing on master

gh-ost --conf=.my.cnf --database=mydb --table=mytable --verbose --alter="engine=innodb" --execute --initially-drop-ghost-table --initially-drop-old-table -max-load=Threads_connected=30 --switch-to-rbr --chunk-size=2500 --cut-over=two-step --exact-rowcount --verbose

What's in a name?

Originally this was named gh-osc: GitHub Online Schema Change, in the likes of Facebook online schema change and pt-online-schema-change.

But then a rare genetic mutation happened, and the s transformed into t. And that sent us down the path of trying to figure out a new acronym. Right now, gh-ost (pronounce: Ghost), stands for:

GitHub Online Schema Translator/Transformer/Transfigurator

Authors

gh-ost is designed, authored, reviewed and tested by the database infrastructure team at GitHub:

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