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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 (EQL) happens to satisfy that.

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

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

project chat

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

Copyright © 2018 - 2019 Hoàng Minh Thắng

Datomic® is a registered trademark of Cognitect, Inc.

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