Skip to content

Instantly share code, notes, and snippets.

@jsmorph
Created July 6, 2012 14:01
Show Gist options
  • Star 7 You must be signed in to star a gist
  • Fork 4 You must be signed in to fork a gist
  • Save jsmorph/3060305 to your computer and use it in GitHub Desktop.
Save jsmorph/3060305 to your computer and use it in GitHub Desktop.
Lucenalog: Datalog interface to Lucene in 10 lines
(ns lucenalog.core
"Lucenalog = Datalog interface to Lucene in 10 lines.
Simple but powerful.
Use
(db/add (index) {:a \"foo\" :b \"bar\"})
to index a map with Lucene. Then you can use the relation
'lucenalog-rel' from core.logic. That relation works on maps. Bound map
values produce a Lucene query, which returns matching maps. See
'lucenalog-test' for an example."
(:require [clucy.core :as db]
[clojure.core.logic :as logic]))
;; (defproject lucenalog "0.0.1-SNAPSHOT"
;; :description "Lucenalog = Datalog interface to Lucene in 10 lines"
;; :dependencies [[org.clojure/clojure "1.2.1"]
;; [clucy "0.3.0"]
;; [org.clojure/core.logic "0.6.6"]
;; ]
;; :main lucenalog.core)
(set! *warn-on-reflection* true)
;; Accessory functions. Not important.
(let [m (ref {:max-query-results 1024
:verbose true})]
(defn config
"Lucenalog configuration. Call with no args to see the current
configuration. Get a configuration property's value by passing the
property to this function. Change the config using the two-argument
dispatch."
([] @m)
([k] (@m k))
([k v] (dosync (alter m assoc k v)))))
(defonce index ;; Get the default Lucene index.
(let [i (db/memory-index)]
(fn [] i)))
(defn- note [& args]
"Println the args if (config :verbose). Return the last arg."
(when (config :verbose)
(apply println :note args))
(last args))
;; Generate the Lucene query string.
(defn- lucene-query
"Query Lucene based on the given object and Substitutions. The
query Q should be a map that has some values bound by substitutions A.
The generated Lucene query string looks like 'p1:v1 AND p2:v2', where
Q contains :p1 lv1 and :p2 lv2 and the substitutions take lv1 to v1 and
lv2 to v2. That query string is then used in the Lucene query."
([q a]
(db/search (index)
(let [walked
(logic/walk* a q)
query
(reduce str
(interpose " AND "
(map (fn [[k v]]
(str (name k) ":" v))
(remove (comp logic/lvar? last)
walked))))]
(note :lucene-search walked q a :query query))
(config :max-query-results))))
;; The core.logic relation.
(defn lucenalog-rel [q]
"A clojure.core.logic relation backed by Lucene. Lucene query
generated by lucene-query based on the given map."
(fn [a]
(logic/to-stream
(map #(logic/unify a % q)
(lucene-query q a)))))
;; Tests and examples.
(defn lucenalog-test
"Simple check that Lucenalog is working. Returns true if things
look okay."
([]
;; Let's use our own in-memory Lucene index.
(binding [index (let [i (db/memory-index)]
(fn [] i))]
(with-open [i ^org.apache.lucene.store.Directory (index)]
;; Add a little data.
(doseq [m [{:a "a1" :b "z1"}
{:a "z1" :b "b1"}
{:a "a1" :b "z2"}
{:a "z1" :b "b2"}]]
(db/add i m))
;; Check to see if we can chase a1 to b1 and b2 via z1.
(let [expect #{"b1" "b2"}
got (set
(logic/run* [q]
(logic/fresh [a b c]
(logic/== a "a1")
(lucenalog-rel {:a a :b b})
(lucenalog-rel {:a b :b c})
(logic/== q c))))
passed? (= expect got)]
(println :test passed? :got got :expected expect)
passed?)))))
(defn -main ([& args] (lucenalog-test)))
@mjul
Copy link

mjul commented Jul 6, 2012

Just a small improvement, instead of (subs (str k) 1) you can write (name k) to get the name of the key, e.g. (name :foo) returns the string "foo".

@jsmorph
Copy link
Author

jsmorph commented Jul 6, 2012

Thanks! Updated.

Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment