Benchmarks: acts-as-taggable-on vs PostgreSQL Arrays

12 years ago

While looking at performance optimizations for a rails project, I noticed these lines in my debug console:

ActsAsTaggableOn::Tag Load (0.5ms)  SELECT "tags".* FROM "tags" INNER JOIN "taggings" ON "tags"."id" = "taggings"."tag_id" WHERE "taggings"."taggable_id" = $1 AND "taggings"."taggable_type" = $2 AND (taggings.context = ('tags'))  [["taggable_id", 103], ["taggable_type", "Prediction"]]

This makes sense, my project is using acts-as-taggable-on to tag models. However, our tagging needs are quite simple, and since we are using postgres, I wondered whether using postgres array types might be more efficient. To get a feel for the basic concept, see 41 studio’s writeup.

However, before going through all the trouble, I’d like to see if the performance gains are appreciable or not. Using rails benchmark functionality, we can do this pretty easily.

Full source code is available at https://github.com/adamnengland/rails-tag-bench, or follow along for the step by step for the full experience.

Getting Started
You’ll need

Rails 4.0.2
Ruby 2.0.0
Postgres.app on OS X – though you can certainly modify this to work with any postgres install

Create a new Rails project

rails new rails-tag-bench
cd rails-tag-bench

Open gemfile and add
gem ‘pg’, ‘0.17.1’

(I had to do this first: gem install pg — –with-pg-config=/Applications/Postgres93.app/Contents/MacOS/bin/pg_config)

Then bundle install to get your dependencies.

Replace config/database.yml with

 1 development:
 2   adapter: postgresql
 3   encoding: unicode
 4   database: rails_tag_bench
 5   pool: 5
 6   username: rails_tag_bench
 7   password:
 8 test:
 9   adapter: sqlite3
10   database: db/test.sqlite3
11   pool: 5
12   timeout: 5000
13 production:
14   adapter: sqlite3
15   database: db/production.sqlite3
16   pool: 5
17   timeout: 5000

We’ll need a database user, so open up postgres and issue:

create user rails_tag_bench with SUPERUSER;

Okay, lets create the database

rake db:create

In postgres type
\c rails_tag_bench
to confirm that the database is set up.

To do this, we’ll also need acts-as-taggable-on, so update the gemfile

gem ‘acts-as-taggable-on’, ‘2.4.1’

and bundle install

rails g acts_as_taggable_on:migration
rake db:migrate

Lets start with the taggable version:

rails g model ArticleTaggable title:string body:text
rake db:migrate

open the created article_taggable.rb and edit

class ArticleTaggable < ActiveRecord::Base
  acts_as_taggable
end

Lets setup the benchmark:

rails g task bench

Fill out the body like so

 1 require 'benchmark'
 2 namespace :bench do
 3   task writes: :environment do
 4     Benchmark.bmbm do |x|
 5       x.report("Benchmark 1") do
 6         1_000.times do
 7           ArticleTaggable.create(:title => ('a'..'z').to_a.shuffle[0,8].join, :body => ('a'..'z').to_a.shuffle[0,100].join, :tag_list =>; ['TAG1'])
 8         end
 9       end
10     end
11   end
12   task reads: :environment do
13     Benchmark.bmbm do |x|
14       x.report("Benchmark 1") do
15         1_000.times do<br />
16           ArticleTaggable.includes(:tags).find_by_id(Random.new.rand(1000..2000));
17         end
18       end
19     end
20   end
21 end

You can run the benchmarks like so:

rake db:reset
rake bench:writes
rake bench:reads

Which should give you output like this:

➜  rails-tag-bench  rake bench:writes
Rehearsal -----------------------------------------------
Benchmark 1   8.620000   0.340000   8.960000 ( 10.716852)
-------------------------------------- total: 8.960000sec
                  user     system      total        real
Benchmark 1   8.540000   0.320000   8.860000 ( 10.543746)

➜  rails-tag-bench  rake bench:reads
Rehearsal -----------------------------------------------
Benchmark 1   2.930000   0.160000   3.090000 (  3.906484)
-------------------------------------- total: 3.090000sec
                  user     system      total        real
Benchmark 1   2.880000   0.150000   3.030000 (  3.825437)

So, on my macbook air, we wrote 1000 records in 10.5437 seconds, and read 1000 records in 3.8254 seconds with acts-as-taggable-on

Now, lets implement the example using postgres arrays, and see where we land

rails g model ArticlePa title:string body:text tags:string

Edit the new migration as follows

 1 class CreateArticlePas < ActiveRecord::Migration
 2   def change
 3     create_table :article_pas do |t|
 4       t.string :title
 5       t.text :body
 6       t.string :tags, array: true, default: []
 7       t.timestamps
 8     end
 9   end
10 end

rake db:migrate

update our benchmarking code:

 1 require 'benchmark'
 2 namespace :bench do
 3   task writes: :environment do
 4     Benchmark.bmbm do |x|
 5       x.report("Using Taggable") do
 6         1_000.times do
 7           ArticleTaggable.create(:title => ('a'..'z').to_a.shuffle[0,8].join, :body => ('a'..'z').to_a.shuffle[0,100].join, :tag_list => ['TAG1'])
 8         end
 9       end
10       x.report("Using Postgres Arrays") do
11         1_000.times do
12           ArticlePa.create(:title => ('a'..'z').to_a.shuffle[0,8].join, :body => ('a'..'z').to_a.shuffle[0,100].join, :tags => ['TAG1'])
13         end
14       end
15     end
16   end
17   task reads: :environment do
18     Benchmark.bmbm do |x|
19       x.report("Using Taggable") do
20         1_000.times do
21           ArticleTaggable.includes(:tags).find_by_id(Random.new.rand(1000..2000));
22         end
23       end
24       x.report("Using Postgres Arrays") do
25         1_000.times do
26           ArticlePa.find_by_id(Random.new.rand(1000..2000));
27         end
28       end
29     end
30   end
31 end

rake db:reset
rake bench:writes
rake bench:reads

The Results

➜  rails-tag-bench  rake bench:writes
Rehearsal ---------------------------------------------------------
Using Taggable          8.520000   0.330000   8.850000 ( 10.532700)
Using Postgres Arrays   1.460000   0.110000   1.570000 (  2.082705)
----------------------------------------------- total: 10.420000sec

                            user     system      total        real
Using Taggable          8.340000   0.310000   8.650000 ( 10.221277)
Using Postgres Arrays   1.410000   0.110000   1.520000 (  2.012559)
➜  rails-tag-bench  rake bench:reads
Rehearsal ---------------------------------------------------------
Using Taggable          2.920000   0.160000   3.080000 (  3.898911)
Using Postgres Arrays   0.420000   0.060000   0.480000 (  0.700684)
------------------------------------------------ total: 3.560000sec
                            user     system      total        real
Using Taggable          2.870000   0.140000   3.010000 (  3.805598)
Using Postgres Arrays   0.400000   0.060000   0.460000 (  0.677917)

For my money, the postgres arrays appear to be much faster, which comes as little surprise. By cutting out all the additional joins, we greatly reduce the query time.

However, it is important to note that this isn’t an apples-to-apples comparison. Acts-As-Taggable-On provides a lot of functionality that simple arrays do not provide. More importantly, this locks you into the postgres database, which may or may not be a problem for you. However, if you really have simplistic tag needs, the performance improvements might be worth it.