has_many filter in RailsAdmin
By Marina Lohova
July 18, 2013
I enjoyed using the RailsAdmin record filtering abilities until one day I needed to find all the orders with the specific product.
class Order < ActiveRecord::Base
has_many :products, :through => :orders_products
end
The following valid piece of RailsAdmin configuration did not break anything but did not work either:
RailsAdmin.config do |config|
config.model Order do
list do
field :products do
searchable :name
end
end
end
end
The reason is that only the belongs_to association is enabled for the search, as stated in the “Field searching” section of the documentation:
(3) Belongs_to associations : will be searched on their foreign_key (:team_id)
or on their label if label is not virtual (:name, :title, etc.)
Benoit Bénézech, creator of RailsAdmin, confirmed this as well:
has_many are not added to the include for perf reason. That means that AR won’t find the :programs table
We only had a few has_many fields configured across the project, so I decided to look into the source code and see if the limitation can be bypassed.
MainController class in RailsAdmin invokes the “get_collection” method to fetch the records for the list action. It defines the “associations” variable which is used to generate SQL query for the filters. I reopened the class in config/initializers/rails_admin_main_controller.rb:
module RailsAdmin
MainController.class_eval do
def get_collection(model_config, scope, pagination)
associations = model_config.list.fields
.select {|f| f.type == :belongs_to_association || f.type == :has_many_association && !f.polymorphic?}
.map {|f| f.association[:name] }
options = {}
options = options.merge(:page => (params[:page] || 1).to_i,
:per => (params[:per] || model_config.list.items_per_page)) if pagination
options = options.merge(:include => associations) unless associations.blank?
options = options.merge(get_sort_hash(model_config))
options = options.merge(:query => params[:query]) if params[:query].present?
options = options.merge(:filters => params[:f]) if params[:f].present?
options = options.merge(:bulk_ids => params[:bulk_ids]) if params[:bulk_ids]
objects = model_config.abstract_model.all(options, scope)
end
end
end
Take a look at the very first line of the method. It used to be:
associations = model_config.list.fields.
select {|f| f.type == :belongs_to_association && !f.polymorphic? }
I allowed for :has_many_association to pass through… and it turned out that RailsAdmin search works perfectly with it!
The SQL output for the Orders list action in RailsAdmin is below:
SELECT * FROM "orders" LEFT OUTER JOIN "orders_products"
ON "orders"."id" = "orders_products"."order_id"
LEFT OUTER JOIN "products" ON "products"."id" = "orders_products.product_id"
WHERE "orders"."id" IN (5469, 5448, 5447, 5436, 5428, 5384, 5007, 4960...)
AND (((products.name ILIKE '%BEER%')))
ORDER BY order.id desc
There is a more exquisite solution to the same problem in the form of a pull request that never got accepted into the official RailsAdmin repo. Use it at your own risk and watch the performance closely.
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