Data dominates. If you’ve chosen the right data structures and organized things well, the algorithms will almost always be self-evident. Data structures, not algorithms, are central to programming. – Rob Pike

Bad programmers worry about the code. Good programmers worry about data structures and their relationships. – Linus Torvalds

Walkable is a serious way to fetch data from SQL for Clojure: Datomic® pull (Graphql-ish) syntax, Clojure flavored filtering and more.

Ever imagined sending queries like this to your SQL database?

Query

Data

Result

[{[:person/by-id 1]
  [:person/id
   :person/name
   :person/age
   {:person/pet [:pet/name :pet/favorite-location]}]}]

Table "person":

id	name	age
1	Mary	20
2	John	15

Table "pet":

id	name	favorite_location
10	Tom	garden
20	Jerry	kitchen

Table "person_pet":

person_id	pet_id
1	10
2	20

{[:person/by-id 1]
 {:person/id   1
  :person/name "Mary"
  :person/age  20
  {:person/pet {:pet/name              "Tom"
                :pet/favorite-location "garden"}}}}

or a bit more sophisticated:

Query

Data

Result

`[{(:articles/all {:filters [:and [:= false :article/hidden]
                             {:article/author [:= :user/username "lucy"]}]})
   [:article/title
    :article/created-date
    {:article/author [:user/id :user/username :user/karma]}]}]

Table "article":

id	title	author_id	hidden	created_date
1	Hello world	10	false	2018-10-11
2	Welcome	20	false	2018-11-10
3	Unfinished	20	true	2018-09-20

Table "user":

id	username	karma
10	mark	21
20	lucy	42

[{:articles/all
  [{:article/title        "Welcome"
    :article/created-date "2018-11-10"
    {:article/author {:user/id       20
                      :user/username "lucy"
                      :user/karma    42}}}]}]

Yes, you can. Have your data fetched in your Clojure mission critical app with confidence. Even more, build the query part of a fulcro server or REST api in minutes today! Call it from your Clojurescript app without worrying about SQL injection.

You can learn about the above query language here

Walkable is NOT about om.next

People may have the impression that Walkable (and Pathom) is specific to om.next. That is NOT the case! Walkable requires a query language that is expressive and based off data structure. Om.next's EDN query language happens to satisfy that.

Walkable's goal is to become the ultimate SQL library for Clojure.

Special thanks to:

Rich Hickey & Cognitect™ team for Clojure and Datomic®
David Nolen for bringing many fresh ideas to the community including om.next
James Reeves for Duct framework. The best development experience I've ever had
Tony Kay for his heroic work on fulcro that showed me how great things can be done
Wilker Lucio for pathom and being very supportive
Sean Corfield for clojure.java.jdbc which we all use extensively
Bozhidar Batsov and CIDER team!!!

Performance

Walkable comes with some optimizations:

A compile phase (floor-plan/compile-floor-plan) that pre-computes many parts of final SQL query strings.
Reduce roundtrips between Clojure and SQL server by combining similar queries introduced by the same om.next join query. (aka N+1 problem)

More optimization will be added. Check github issues for progress.

Limitation

Currently Walkable only takes care of reading from the database, NOT

making mutations to it. I think it varies from applications to

applications. If you can think of any pattern of doing it, please

open an issue.

Support

I'm available for questions regarding walkable on #walkable clojurians slack channel. I'm also on #fulcro and Clojureverse

Legal

Datomic® is a registered trademark of Cognitect, Inc.

Introduction