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    Ongoing observations by End Point Dev people

    has_many filter in RailsAdmin

    Marina Lohova

    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

    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 

    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)

    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.