Requirements
============

You will need to download ssdeep (tested with 2.1 and 2.5) from http://ssdeep.sourceforge.net/ and then configure and make as usual.

Installation
============

You will want to clone this repository in the contrib folder of your postgres source folder, and then you should be able to run "make" and "make install".

To expose the ssdeep functions in your database, you'll need to issue the following statements:

  CREATE OR REPLACE FUNCTION fuzzy_hash(TEXT) RETURNS TEXT AS 'ssdeep_psql.so', 'pg_fuzzy_hash' LANGUAGE 'c';
  CREATE OR REPLACE FUNCTION fuzzy_compare(TEXT, TEXT) RETURNS INTEGER AS 'ssdeep_psql.so', 'pg_fuzzy_compare' LANGUAGE 'c';
  CREATE OR REPLACE FUNCTION fuzzy_hash_compare(TEXT, TEXT) RETURNS INTEGER AS 'ssdeep_psql.so', 'pg_fuzzy_hash_compare' LANGUAGE 'c';

Usage
=====

ssdeep_psql exposes three functions for working with fuzzy hashes: fuzzy_hash, fuzzy_compare, and fuzzy_hash_compare:

  # select fuzzy_hash('john');
   fuzzy_hash
   ------------
    3:Uvl

  # select fuzzy_compare('lorem ipsum dolor sit amet', 'lorem ipsum dolor sit amet');
   fuzzy_compare
   ---------------
                9

  # select fuzzy_hash_compare('3:JBo8MRwRn:J3PR', '3:JBo8MRwx:J3Px');
   fuzzy_hash_compare
   --------------------
                     8

Here's a suggested workflow for using ssdeep_psql:

  CREATE TABLE "stories" ("id" SERIAL, "body" TEXT, "hash" TEXT);

  CREATE OR REPLACE FUNCTION set_fuzzy_hash() RETURNS TRIGGER AS $$
  BEGIN
      NEW.hash := fuzzy_hash(NEW.body);
      RETURN NEW;
  END;
  $$ LANGUAGE plpgsql;
  CREATE TRIGGER "set_fuzzy_hash_for_body_on_insert" BEFORE INSERT ON "stories"
    FOR EACH ROW EXECUTE PROCEDURE set_fuzzy_hash();
  CREATE TRIGGER "set_fuzzy_hash_for_body_on_update" BEFORE UPDATE ON "stories"
    FOR EACH ROW EXECUTE PROCEDURE set_fuzzy_hash();

  INSERT INTO "stories" ("body") VALUES ('Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua.');
  INSERT INTO "stories" ("body") VALUES ('Ut enim ad minim veniam, quis nostrud exercitation ullamco laboris nisi ut aliquip ex ea commodo consequat.');

  SELECT id, fuzzy_compare(body, 'Lorem ipsum dolor sit amet') as score from "stories" ORDER BY fuzzy_compare(body, 'Lorem ipsum dolor sit amet') DESC LIMIT 1;

  -- or, much faster
  SELECT id, fuzzy_hash_compare(hash, fuzzy_hash('Lorem ipsum dolor sit amet')) as score from "stories"
  ORDER BY fuzzy_hash_compare(hash, fuzzy_hash('Lorem ipsum dolor sit amet')) DESC LIMIT 1;

  -- and again, assuming you've calculated your search text's hash already (with, say, ssdeep_ruby)
  SELECT id, fuzzy_hash_compare(hash, '3:f4oo8MRwRn:f4kPR') as score from "stories"
  ORDER BY fuzzy_hash_compare(hash, '3:f4oo8MRwRn:f4kPR') DESC LIMIT 1;