VirtualAttributes allows you to define a ruby method that acts like an attribute or relation.
Sometimes you have a model with an attribute defined in ruby but you want to sort or filter by it. Filtering by that attribute necessitates fetching all the rows from the database and filtering in ruby. For large tables, this is slow and takes up a lot of memory.
This gem allows you to represent these attributes in sql so
WHERE clauses will work.
This also allows you to calculate counts and treat those as a field accessible with
select(:child_count) to get rid of the N+1 problem of running a
count(*) on a subcollection for each row.
Add this line to your application's Gemfile:
And then execute:
Or install it yourself as:
$ gem install activerecord-virtual_attributes
TODO: Write usage instructions here
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.
To test with different versions of ruby, use
wwtd gem or
DB=pg BUNDLE_GEMFILE=gemfiles/gemfile_$version-52.gemfile bundle exec rake
Bug reports and pull requests are welcome on GitHub at https://github.com/ManageIQ/activerecord-virtual_attributes .
This project is available as open source under the terms of the Apache License 2.0.