在Clojure中，如何配置Korma和Ragtime使用相同的数据库？

Question

I'm trying to work with databases in Clojure. At this point, I want to use Ragtime to modify the database schema itself, Korma to query and insert data, and H2 as the actual database.

I think I'm using them properly, but I'm getting an error when I try to use Korma to access a table.

Here's my project.clj:

(defproject dbexplore "0.1.0-SNAPSHOT"
  :dependencies [[org.clojure/clojure "1.6.0"]
                 [korma "0.4.0"]
                 [com.h2database/h2 "1.4.182"]
                 [ragtime "0.3.7"]]
  :plugins [[ragtime/ragtime.lein "0.3.7"]]
  :ragtime {:migrations ragtime.sql.files/migrations
            :database "jdbc:h2:/home/zck/Documents/dbexplore/resources/db/dbexplore.db"}
  :main dbexplore.core)

So I'm importing korma, h2database, and ragtime. I'm not sure it's pointing the Ragtime migration at the proper database location.

I created a migration file with this as the contents:

create table users (id INT, first varchar(32), last varchar(32));

And then ran it:

zck@zck-desktop:~/Documents/dbexplore$ lein ragtime migrate
Applying 2014-10-22-2-11-create-tables

I made a simple core.clj file that just selects everything from the users table:

(ns dbexplore.core
  (:require [korma.db :as db]
            [korma.core]))

(def db-connection (db/h2 {:db "./resources/db/dbexplore.db"}))

(db/defdb korma-db db-connection)

(korma.core/defentity users)

(defn -main []
  (korma.core/select users))

But upon running it with lein run , I get an error:

Failure to execute query with SQL:
SELECT "users".* FROM "users"  ::  []
JdbcSQLException:
 Message: Table "users" not found; SQL statement:
SELECT "users".* FROM "users" [42102-182]
 SQLState: 42S02
 Error Code: 42102
Exception in thread "main" org.h2.jdbc.JdbcSQLException: Table "users" not found; SQL statement:
SELECT "users".* FROM "users" [42102-182], compiling:(/tmp/form-init7833348906040195763.clj:1:90)

My suspicion is that I'm pointing at a different database file in the h2 call in core.clj from the one ragtime is migrating, but I'm not sure how to specify it properly. How can I make these two libraries use the same database?

Answer 1

I created an issue in korma: https://github.com/korma/Korma/issues/273
Maybe you want to add something.

I was able to read the data from the h2 database with yesql instead of korma. According to different threads it should be possible to use mysql or postgresql instead of h2, but I have not tried that.

Btw. I have successfully used datomic for my last sideprojects with none of these problems, so don't give up, just try a different setup.

UPDATE Please have a look at the linked bug, the maintainer posted two solutions, which both do work for me.