Lazy import of csv file in Clojure

I’ve been looking at Clojure now and then for a while… really wanna learn this stuff :) The other day I needed to import a very large CSV file… and it seemed like a good problem to try solve in Clojure.

I’m using Leiningen and started with the following project setup.


(defproject bbr "1.0.0"
  :description "Import BBR data"
  :dependencies [[org.clojure/clojure "1.3.0"]
                 [org.clojure/clojure-contrib "1.2.0"]
                 [org.clojure/java.jdbc "0.0.6"]
                 [mysql/mysql-connector-java "5.1.6"]
                 [clojure-csv "2.0.0-alpha2"]])


(ns bbr.core
  (:require [clojure-csv.core :as csv]
            [ :as sql])
  (:use [ :only [reader]]))

(def db {:classname "com.mysql.jdbc.Driver"
         :subprotocol "mysql"
         :subname "//localhost:3306/mydb"
         :user "root"})

(defn parse-row [row]
  (let [v (first (csv/parse-csv row :delimiter \;))]
    (zipmap [:kvhx :road :no :floor :door :zip_code :city] v)))

(defn parse-file
  (with-open [file (reader filename :encoding "ISO-8859-1")]
    (sql/with-connection db
      (doseq [line (line-seq file)]
        (let [record (parse-row line)]
          (sql/update-or-insert-values "bbr" ["kvhx=?" (:kvhx record)] record))))))

The above should be able to import VERY large CSV files into the database because it reads one line from the file at the time.

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Lazy import of csv file in Clojure by Jacob Emcken is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.