Jsonapi::QueryBuilder

Jsonapi::QueryBuilder serves the purpose of adding the json api query related SQL conditions to the already scoped collection, usually used in controller index actions.

With the query builder we can easily define logic for query filters, attributes by which we can sort, and delegate pagination parameters to the underlying paginator. Included relationships are automatically included via the ActiveRecord::QueryMethods#includes, to prevent N+1 query problems.

Installation

Add this line to your application's Gemfile:

gem 'jsonapi-query_builder'

And then execute:

$ bundle install

Or install it yourself as:

$ gem install jsonapi-query_builder

Usage

class UserQuery < Jsonapi::QueryBuilder::BaseQuery
  ## pagination 
  paginator Jsonapi::QueryBuilder::Paginator::Pagy # default paginator

  ## sorting
  default_sort created_at: :desc
  sorts_by :last_name
  sorts_by :first_name, ->(collection, direction) { collection.order(name: direction) }
  sorts_by :email, EmailSort

  ## filtering
  filters_by :first_name
  filters_by :last_name
  filters_by :email, ->(collection, query) { collection.where('email ilike ?', "%#{query}%") }
  filters_by :type, TypeFilter
  filters_by :mrn, MrnInMemoryFilter
end

class UsersController < ApplicationController
  def index
    user_query = UserQuery.new(User, params.to_unsafe_hash)

    render json: user_query.results, status: :ok
  end
end

The query class is initialized using a collection and query parameters. Since query parameters are referenced explicitly we can pass them as an unsafe hash. Jsonapi::QueryBuilder::BaseQuery should not be responsible for scoping records based on current user permissions, or for any other type of scoping. It's only responsibility is to support the json:api querying. Use pundit or similar for policy scoping, custom query objects for other scoping, and then pass the scoped collection to the Jsonapi::QueryBuilder::BaseQuery object.

Pagination

Pagination support is configurable using the paginator method to define the paginator. It defaults to the Pagy paginator, a lightweight and fast paginator. Other paginators currently supported are Kaminari and an implementation of keyset pagination. Before using these paginators we need to explicitly require the gems in our Gemfile and the paginator file in question. Additionally one can implement it's own paginator by inheriting from Jsonapi::QueryBuilder::Paginator::BasePaginator. The minimum required implementation is a #paginate method that receives page params and returns a page of the collection. It can return the pagination details as the second item of the returned array, that can be used in the serializer for pagination metadata.

Using the Kaminari Paginator

require "jsonapi/query_builder/paginator/kaminari"

paginator Jsonapi::QueryBuilder::Paginator::Kaminari

Using the Keyset Paginator

require "jsonapi/query_builder/paginator/keyset"

paginator Jsonapi::QueryBuilder::Paginator::Keyset

Sorting

Ensuring deterministic results

Sorting has a fallback to an unique attribute which defaults to the id attribute. This ensures deterministic paginated collection responses. You can override the unique_sort_attribute in the query object.

# set the unique sort attribute
unique_sort_attribute :email
# use compound unique sort attributes
unique_sort_attributes :created_at, :email

Default sort options

The default_sort can be set to sort by any field like created_at timestamp or similar. It is only used if no sort parameter is set, unlike the unique_sort_attribute which is always appended as the last sort attribute. The parameters are passed directly to the underlying active record relation, so the usual ordering options are possible. It is also possible to define the default sort with a lambda or by passing a sort object.

default_sort :created_at
# or
default_sort created_at: :desc
# or
default_sort ->(collection) { collection.order(created_at: :desc) }
# or
default_sort SortObject

Enabling simple sorting for attributes

sorts_by denotes which attributes can be used for sorting. Sorting parameters are usually parsed from the json:api sort query parameter in the order they are given. So sort=-first_name,email would translate to { first_name: :desc, email: :asc }

sorts_by :first_name
sorts_by :email

Sorting with lambdas

sorts_by also supports passing a lambda to implement a custom order or reorder function. The parameters passed to the lamdba are collection and the direction of the order, which is either :desc or :asc.

sorts_by :first_name, ->(collection, direction) { collection.order(name: direction) }

Sorting with sort classes

But since we're devout followers of the SOLID principles, we can define a sort class that responds to #results method, which returns the sorted collection. Under the hood the sort class is initialized with the current scope and the direction parameter.

Filtering

Simple exact match filters

filters_by :first_name
# => collection.where(first_name: params.dig(:filter, :first_name)) if params.dig(:filter, :first_name).present?

Lambda as a filter

filters_by :email, ->(collection, query) { collection.where('email ilike ?', "%#{query}%") }
# => collection.where('email ilike ?', "%#{params.dig(:filter, :email)}%") if params.dig(:filter, :email).present?

Filter classes

We can define a filter class that responds to #results method, which returns the filtered collection results. Under the hood the filter class is initialized with the current scope and the query parameter. However, if the object responds to a call method it sends the current scope and the query parameter to that instead. This is great if you're using query objects for ActiveRecord scopes, you can easily use them to filter with as well.

filters_by :type, TypeFilter

The filter class could look something like

class TypeFilter < Jsonapi::QueryBuilder::BaseFilter
  def results
    collection.where(type: query.split(','))
  end
end

Sometimes you need to perform in-memory filtering, for example when database attributes are encrypted. In that case, those filters should be applied last, the order of definition in the query object matters.

class MrnFilter < Jsonapi::QueryBuilder::BaseFilter
  def results
    collection.select { |record| /#{query}/.match?(record.mrn) }
  end
end

Additional Options

You can override the filter query parameter name by passing the query_parameter option.

filters_by :first_name, query_parameter: 'name'
# => collection.where(first_name: params.dig(:filter, :name)) if params.dig(:filter, :name).present?

allow_nil option changes the filter conditional to allow explicit checks for an attribute null value.

filters_by :first_name, allow_nil: true
# => collection.where(first_name: params.dig(:filter, :first_name)) if params[:filter]&.key?(:first_name)

The conditional when the filter is applied can also be defined explicitly. Note that these options override the allow_nil option, as the condition if defined explicitly and you should handle nil explicitly as well.

filters_by :first_name, if: ->(query) { query.length >= 2 }
# => collection.where(first_name: params.dig(:filter, :first_name)) if params.dig(:filter, :first_name) >= 2
filters_by :first_name, unless: ->(query) { query.length < 2 }
# => collection.where(first_name: params.dig(:filter, :first_name)) unless params.dig(:filter, :first_name) < 2

When you're using a filter class you can pass a symbol to the :if and :unless options which invokes the method on the filter class.

filters_by :type, TypeFilter, if: :correct_type?
# => type_filter = TypeFilter.new(collection, query); type_filter.results if type_filter.correct_type?

Development

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.

We're using standardrb and lefthook. You can install lefthook hooks via lefthook install. It will run linters and standardrb checks before commits, and a bundle audit + whole spec suite before push.

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 LEFTHOOK=0 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.

Contributing

Bug reports and pull requests are welcome on GitHub at https://github.com/infinum/jsonapi-query_builder.

License

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