What the difference between oj and korma? about oj

[taylorlapeyre]

In korma, SQL queries are compiled by calling functions. In OJ, everything is just data. Queries are represented as a Clojure (query) map that can be manipulated however you wish.

In korma,

(select user
  (fields :firstName :lastName)
  (where {:email "[email protected]"}))

In OJ:

{:table :users
 :select [:firstName :lastName]
 :where {:email "[email protected]"}}

OJ encourages the use of "modifier functions," which take a query map, change it, and return a new one.

(-> (query :users)
    (select  [:firstName :lastName])
    (where {:email "[email protected]"})
    (oj/exec database))

This gives the appearance of a higher level library abstraction, without losing the "everything is just data" mentality.

[razum2um]

korma also allows you to do (def scope (-> (select* table) (where {:col true}))

it's a clojure map too, and you can modify it as you wish, but there are quite good functions already some like limit, order and so on ending up in sqlfn and raw as well.
(-> scope (limit 1)) returns scope-map again until calling (-> scope (select))

one known to me korma's limitation is unability to write CTE and with queries for postgres for example.
do you solve this one?

[taylorlapeyre]

The "with" problem is one that I struggled to solve in a way that was acceptable to me. In the end, I went with the concept of a join, which you can find documentation for here.

The default modifier function join tries to be as helpful as possible. If your tables are named in a rails convention, joining another table is as simple as:

(-> (query :users)
    (join :items))
; => SELECT * FROM users
; => SELECT * FROM items WHERE items.user_id = 1
; => SELECT * FROM items WHERE items.user_id = 2
; ... and so on for each user

If not, you can specify the foreign keys:

(-> (query :users)
    (join :items {:user_id :id})

The returned result would look like this:

({:username "blah" :items ({:id 1 :name "Thing"})} ...

I plan on parallelising these subqueries.

[razum2um]

1. under "with" I meant http://www.postgresql.org/docs/9.3/static/queries-with.html
2. such relying on conventions does appeal to me and i like rails way as well, but would you like to turn it to includes-like?

Anyway, still don't get you why not to join forces and fork korma to push mainstream further?
As I said, it modifies similar map under the hood, but nothing prevents you to modify it by yourself

[taylorlapeyre]

1. Ah.. yes. In that sense, with is yet to come.
2. Maybe.

Korma is a great project! I just feel like there can be a simpler, easier to understand, and more elegant solution to interfacing with a database. Forking Korma would mean changing a lot of their API, which means that it would basically be a new project anyway. OJ is my personal solution.

[razum2um]

Ok, thanks then and good luck!

[taylorlapeyre]

Thanks for your interest!