dsm

dsm (short for "dead simple migrations") is a small Clojure library designed to run migration functions.

Migrations are given as a map of names to functions. "Up" migration names start with -UP-, and "down" migration names start with -DOWN-.

dsm.core contains the logic for deciding which migrations to run, and dsm.sql contains utilities for running those against a JDBC connection spec (as well as maintaining a migrations table).

dsm.sql depends on a working SQL database connection, which is used to record migration progress and is given as the first argument to all migration functions.

[dsm "0.0.4-SNAPSHOT"]

Usage

(ns my-awesome-app.schema
    (:require [dsm.sql :refer [create-migrations-table migrate-up migrate-down]]
              [hugsql.core :refer [map-of-db-fns-from-string]]))

(def conn {:classname "org.sqlite.JDBC"
           :subprotocol "sqlite"
           :subname "./resources/awesome.db"})

; First, using the magic of HugSQL, define migrations
(def migrations (map-of-db-fns-from-string "
-- :name -UP-m1-wal-pragma :*
pragma journal_mode = WAL;

-- :name -DOWN-m1-wal-pragma :?
select 1; -- does nothing, this pragma is permanent

-- :name -UP-m2-foreign-key-pragma :!
pragma foreign_keys = on;

-- :name -DOWN-m2-foreign-key-pragma :?
pragma foreign_keys = off;

-- :name -UP-m3-create-users-table :!
create table if not exists \"users\" (
  \"id\" integer primary key autoincrement not null,
  \"created_at\" integer not null,
  \"username\" char(128) not null,
  \"access_token\" char(128) not null
);
-- :name -DOWN-m3-drop-users-table :!
drop table if exists \"users\";

-- :name -UP-m4-create-unique-username-index :!
create unique index if not exists user_usernames on \"users\" (\"username\");

-- :name -DOWN-m4-drop-unique-username-index :!
drop index if exists user_usernames;
"))

; Next, we create a place to store our migration state
(create-migrations-table conn)

; Finally, run any pending migrations!
(migrate-up conn migrations) 

; We can roll back to a target version
(migrate-down conn migrations 3)

; And migrate up again to a desired version
(migrate-down conn migrations 4)

License

Copyright © 2019 Duncan Smith

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