Ragtime is a Clojure library for migrating structured data in a way that's database independent. It defines a common interface for expressing migrations, much like Ring defines a common interface for expressing web applications.

Add the following dependency to your deps.edn file:

dev.weavejester/ragtime {:mvn/version "0.11.0"}

Or to your Leiningen project file:

[dev.weavejester/ragtime "0.11.0"]

Ragtime needs a minimum of three things to work:

1. A migratable data store
2. An ordered sequence of migrations
3. A strategy on how to deal with conflicts

A data store is an implementation of the DataStore protocol, and tells Ragtime how to record which migrations are applied to an arbitrary store of data, such as a database. It has three methods:

• add-migration-id - add a new migration ID to the store
• remove-migration-id - remove a migration ID from the store
• applied-migration-ids - return an ordered list of applied IDS

Migrations are implementations of the Migration protocol, which also has three methods:

• id - returns a unique ID for the migration
• run-up! - applies the migration to a database
• run-down! - rolls back the migration in a database

Ragtime comes with implementations of these protocols for Cloure's java.jdbc library and Sean Corfield's next.jdbc library, therefore supporting SQL migrations out of the box.

The migration store for SQL database is a special migrations table, and the migrations can be specified as either .sql files, or .edn files. For more information, see the documentation below.

Some Ragtime functions require one more element: a migration index. This should satisfy the MigrationIndex protocol, which has three methods:

• index-migration - index a migration by key
• deindex-migration - remove a migration from the index
• get-indexed-migration - get an indexed migration by key

This is used for storing migration information. By default this protocol is satisfied by an ordinary Clojure map, but could be attached to a persistence layer.

• Getting Started
• Upgrading from 0.3.x
• Upgrading from 0.4.x
• Concepts
• SQL Migrations
• Leiningen Integration
• API docs
• Third-party Libraries

Copyright © 2024 James Reeves

Distributed under the Eclipse Public License either version 1.0 or (at your option) any later version