Building a Simple Redis Autosuggest with Ruby

So you have a search box on your website.. an article search, a product search.. whatever it may be, you may find yourself the need to display suggested results to your user based on what they type. Redis is the perfect solution.


Let's say we have a bunch of products:

  • Tommy's Ray Gun - ID: 1
  • 1990 Blaster Ray!! - ID: 2
  • (Nuke) Bomb Gun #8 - ID: 3

Looking at our products, we can see there is a different and unpredictable titles. We have punctuation, special characters, numbers, and letters. If someone types Gun we'd like to see our search suggest (Nuke) Bomb Gun #8 and Tommy's Ray Gun.

Redis does not offer a full-text search solution like ElasticSearch, so we simply can't drop Tommy's Ray Gun string into Redis and expect to search it. We need to come up with a clever way.

My solution was to split each letter up of each word in each product. For each letter set, we store the products which contain those letters. So common sets of letters in titles will be stored together.

As a basic example, lets look at a singular word. RUBY we can split this up into R then RU then RUB and finally RUBY.

Lets store these product titles in this manner with the values being the title and ID for the product into a Redis sorted set. Now, when someone types gun in your search box we should be able to call p:gun key on Redis and get:

  • Tommy's Ray Gun//1
  • (Nuke) Bomb Gun #8//3

Processing the Objects

So now we have a plan in place, lets write a quick script to import the objects you wish to autosuggest, into your Redis database. As before, we need to split each word up of each object.

# autosuggest.rb
require "redis"

redis =
redis.flushdb # Resets to a clean database

def clean_title(title)
    # Change to your needs
    title.downcase.gsub(/-/, " ").gsub(/[^0-9a-z ]/, "")

# Our list of products
products = [
  {id: 1, title: "Tommy's Ray Gun"},
  {id: 2, title: "1990 Blaster Ray!!"},
  {id: 3, title: "(Nuke) Bomb Gun #8"}

products.each do |product|
  puts "Processing #{product[:title]}..."

  # Clean the title, split up into parts
  clean_title(product[:title]).split(" ").each do |part|
      1.upto(part.length) do |len|
          next if len == 1 # So we do not have a key of 1 length

          # Output a piece of each part
          puts part[0...len]

If you run this into your terminal it should output:

> ruby autosuggest.rb
Processing Tommy\'s Ray Gun...
"to" "tom" "tomm" "tommy" "tommys" "ra" "ray" "gu" "gun"
Processing 1990 Blaster Ray!!...
"19" "199" "1990" "bl" "bla" "blas" "blast" "blaste" "blaster" "ra" "ray"
Processing (Nuke) Bomb Gun #8...
"nu" "nuk" "nuke" "bo" "bom" "bomb" "gu" "gun"

Here we can see how the script cleans the titles, then breaks them down to produce key names for Redis to use as we had hoped for in the planning section. Now, lets import this into Redis. Simply change line 27:

puts part[0...len]

redis.zadd "p:#{part[0...len]}", 0, "#{product[:title]}//#{product[:id]}"

This will now store the titles for the objects as planned into a sorted list on Redis, where common sets of parts will group objects together. Go ahead and run your script again.

> ruby autosuggest.rb
Processing Tommy's Ray Gun...
Processing 1990 Blaster Ray!!...
Processing (Nuke) Bomb Gun #8...

Login to Redis and lets check if it works as planned. Since this is a sorted set we need to use ZRANGE.

> redis-cli> ZRANGE p:gun 0 -1
1) "(Nuke) Bomb Gun #8//3"
2) "Tommy's Ray Gun//1"> ZRANGE p:nuke 0 -1
1) "(Nuke) Bomb Gun #8//3"

Awesome, it works! We now have sorted sets with groups of products based on parts of the words in the object titles.


Now that we have a script (that you should expand on into a proper lib), we need to now show results to the user for when they're searching.

Heres a quick Sinatra example (of course you can use more advanced techniques as well)

require "redis"
require "json"
require "securerandom"
require "sinatra/base"
require "sinatra/jsonp"

module YourApp
  class AutoComplete < Sinatra::Base
    helpers Sinatra::Jsonp

    configure {set :redis,}

    get "/" do
      # Clean the query and get each word
      sets = []
      clean_query(params["q"]).split(" ").each {|word| sets << "p:#{word}"}

      # Get the common results in a temporary key
      tmp_key = "tmp_#{SecureRandom.uuid[0...8]}"
      settings.redis.zinterstore tmp_key, sets
      results = settings.redis.zrange tmp_key, 0, -1
      settings.redis.del tmp_key

      # Output results as JSON to browser
      jsonp results.to_json

    def clean_query(query)
      # Remove all special characters and adjusts naming
      query.downcase.gsub(/-/, " ").gsub(/[^0-9a-z ]/, "")

By calling /?q=some+text, we create a key for each word passed. So some+text goes into the sets variable and becomes ["p:some", "p:text"].

Next, we create a temporary key to use with zinterstore which computes intersection between keys (our p:some and p:text). This finds products that have both the words some and text in their title. We then use zrange to get the result of the intersection and delete the temporary key.

Finally, send the results as JSON. You can use AJAX to actively call the Sinatra app when the user is typing.

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