generations

A Clojure library designed to support simple database schema migrations for Datomic.

Usage

This library allows to simply keep syncronized schema attributes in all the databases on different machines, such as developers' local machines, staging, production, etc.

For this, we use the idea of "generation": it is a plain transaction request, a list of lists or list of maps with transaction data. And you have to keep all the generations in a vector. To evolve database schema, new generation should be added to the end of this vector.

In other words, you always keep schema related transactions ordered in this vector:

(def my-project-generations
  [

   ;; -*- Generation 1 -*-

   [
	   {:db/id #db/id[:db.part/db]
	    :db/ident :user/id
        :db/valueType :db.type/uuid
        ...
	    :db.install/_attribute :db.part/db}

	   {:db/id #db/id[:db.part/db]
	    :db/ident :user/email
        :db/valueType :db.type/string
        ...
	    :db.install/_attribute :db.part/db}

	   {:db/id #db/id[:db.part/db]
	    :db/ident :enums
	    :db.install/_parition :db.part/db}
   ]

   ;; -*- Generation 2 -*-

   [
	   {:db/id #db/id[:enums] :db/ident :locale/en}
	   {:db/id #db/id[:enums] :db/ident :locale/nl}
	   {:db/id #db/id[:enums] :db/ident :locale/it}

	   {:db/id #db/id[:db.part/db]
	    :db/ident :user/address
        :db/valueType :db.type/string
        ...
	    :db.install/_attribute :db.part/db}

	]

	...

   ])

ilshad.generations/install automatically installs only generations which are not installed yet:

(ilshad.generations/install my-project-generations db-conn)

For example, put this into your main function to ensure actual database schema always installed:

(ns my-project
  (:require [datomic.api :as d]
            [ilshad.generations :as generations]))

(defn -main [& args]
  (let [uri "datomic:dev://localhost:4334/my-database"]
    (when (d/create-database uri)
	  (log/info "New database has been created:" uri))
    (generations/install my-project-generations (d/connect uri))))

To achieve its goal, this library installs :generation/id and :generation/data attributes into the database and thus it stores an information about all the generations.

License

Copyright © 2013-2016 Ilshad Khabibullin.

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