Introduction
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.
Bad programmers worry about the code. Good programmers worry about data structures and their relationships.
Walkable is a serious way to fetch data from SQL for Clojure: Datomic® pull (Graphql-ish) syntax, Clojure flavored filtering and more.
At a glance
Ever imagined sending queries like this to your SQL database?
[{[:person/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/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:
`[{(:articles/articles {: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/articles
[{: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 Fulcro
People may have the impression that Walkable (and Pathom) is specific to Fulcro. That is NOT the case! Walkable requires a query language that is expressive and based off data structure. Fulcro’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 EQL join. (aka N+1 problem)
-
Planning phase for repeated queries.
-
Reusable queries with placeholders.
More optimization will be added. Check github issues for progress.
Limitation / Non-goal
-
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.
With other SQL libraries
-
Let Walkable covers majority (say 80%???) of your boring queries - ones that are repetitive and predictable.
-
Let clojure.java.jdbc / next.jdbc do simple insert/update operations.
-
In case you want to write manual queries for performance reason, or complex transaction behaviors, you should definitely leave that to Honeysql / Hugsql / penkala.
Support
Chat
I’m available for questions on #walkable clojurians channel. I’m
also on #fulcro and Clojureverse