datomic_getting_started.md

Datomic getting started

datomic API

Javascript driver

You can also access Datomic from Javascript, such as from a Node.js app (which could be written in ClojureScript)

datomicjs

Usage

See datomic.js

Datomic(server, port, alias, name)

Create Schema:

schema.movies = '[
  {:db/id #db/id[:db.part/db]
   :db/ident :movie/title
   :db/valueType :db.type/string
   :db/cardinality :db.cardinality/one
   :db/doc "movie's title"
   :db.install/_attribute :db.part/db}'
   '

Then use...

Datomic = require('datomicjs').Datomic;
imdb = new Datomic('localhost', 8888, 'db', 'imdb');

// use the DB
imdb.transact(...);

datomic.transact(schema.movies).then((future) ->
  console.log(future);


// to build a Query
find = require('datomicjs').Query;
find('?m')
  .where('?m', ':movie/title', 'trainspotting')
  .toString()
...

API

imdb.transact(data)
imdb.entity(id, opts)
imdb.q(query, opts)

EDN

parse EDN and serialize EDN are used to work with the Clojure Map structures of Datomic. The interop with Clojure is done by taking a string with the Map syntax and serializing it to EDN (for queries etc) and conversely parsing a received EDN structure from Datomic (ie. data).

Clojure

Add the following dependencies to your project.clj file:

:dependencies [
    ;; SERVER
    [org.clojure/clojure "1.8.0"]

    ;; Server DB (datomic)
    [com.datomic/datomic-free "0.9.5327" :exclusions [joda-time]]
    ;; ...
]

Then for your app file ,such as my-app.core

See [Datomic API]((http://docs.datomic.com/clojure/#datomic.api) for API details.

(ns my-app.core
  (:require [datomic :as d]
            ;; more libs...
            ))

;;; Create a DataScript "connection" (an atom with the current DB value)
(def conn (d/create-conn))

;; Define datoms to transact
(def datoms [{:db/id -1 :name "Bob" :age 30}
             {:db/id -2 :name "Sally" :age 15}])

;;; Add the datoms via transaction
(d/transact! conn datoms)

;;; Query to find names for entities (people) whose age is less than 18
(def q-young '[:find ?n
               :where
               :in ?min-age
               [?e :natedme ?n]
               [?e :age ?a]
               [(< ?a ?min-age)]])

;; execute query: q-young, passing 18 as min-age
(d/q q-young 18)

;; Query Result
;; => [["Sally"]]

As you can see, for this simple example the API is identical to the one used for our Datascript getting started code example.