QuickCount

Unfortunately, it's currently notoriously difficult and expensive to get an exact count on large tables.

Luckily, there are some tricks for quickly getting fairly accurate estimates. For example, on a table with over 450 million records, you can get a 99.82% accurate count within a fraction of of the time. See the table below for an example dataset.

Supports:

• PostgreSQL
  • Multi-table Inheritance

These metrics were pulled from real databases being used in a production environment.

Add this line to your application's Gemfile:

gem 'quick_count'

And then execute:

$ bundle

Or install it yourself as:

$ gem install quick_count

To finish the install, in rails console:

$ QuickCount.install # Install with default (500000) threshold

# user.rb

QuickCount.install # Install with default (500000) threshold

# Change the threshold for when `quick_count` kicks in...
QuickCount.install(threshold: 500000)

class User < ActiveRecord::Base

end

User.quick_count

# Override the default threshold on a case-by-case basis.
User.quick_count(threshold: 600000)

Remove this line to your application's Gemfile:

gem 'quick_count'

And then execute:

$ bundle

And in a rails console:

$ QuickCount.uninstall

Released under the MIT license - http://opensource.org/licenses/MIT

After checking out the repo, run bin/setup to install dependencies. Then, run rake spec to run the tests. You can also run bin/console for an interactive prompt that will allow you to experiment.

To install this gem onto your local machine, run bundle exec rake install. To release a new version, update the version number in version.rb, and then run bundle exec rake release, which will create a git tag for the version, push git commits and tags, and push the .gem file to rubygems.org.

Bug reports and pull requests are welcome on GitHub at https://github.com/TwilightCoders/quick_count.

The gem is available as open source under the terms of the MIT License.