I have a sample data set in a txt file. The data file is extremely large so loading it in memory is not an option. I need to be able to read the file lazily. Furthermore, I need the lines to be read in a random order. And there might be cases where I don't need to read all the lines. This is what I found so far -
(defn read-lazy [in-file] (letfn [(helper [rdr] (if-let [line (.readLine rdr)] (cons line (helper rdr)) (do (.close rdr) nil)))] (helper (io/reader in-file))))
which returns a lazy-seq of the file. How can I loop through random lines in the lazy-seq when I need to? I think using a go block could help here. Go blocks could put a random line in a channel and await for something to consume it. Once the data gets read it puts another line in the channel awaits for the next read. How can I implement that?
Here's how I've worked it out (not random) -
(def lazy-ch (chan)) (defn async-fetch-set [in-file] (go (with-open [reader (io/reader in-file)] (doseq [line (line-seq reader)] (>! lazy-ch line))) (close! lazy-ch))) (println "got: " (<!! lazy-ch))
Is this a good way to approach the problem? Is there a better solution? I might not need to read all the lines so I'd like to be able to close the reader if whenever I need to.