Optimize HABTM query (#73)

Could cause n+1 as the association table is joined, but not eager
loaded.

Author: richmolj

lib/jsonapi_compliable/adapters/active_record_sideloading.rb

@@ -76,7 +76,11 @@ def has_and_belongs_to_many(association_name, scope: nil, resource:, foreign_key
             parent_ids = parents.map { |p| p.send(primary_key) }
             parent_ids.uniq!
             parent_ids.compact!
-            _scope.call.joins(through).where(through => { fk => parent_ids }).distinct
+            _scope.call
+              .joins(through)
+              .preload(through) # otherwise n+1 as we reference in #assign
+              .where(through => { fk => parent_ids })
+              .distinct
           end
 
           assign do |parents, children|

lib/jsonapi_compliable/version.rb

@@ -1,3 +1,3 @@
 module JsonapiCompliable
-  VERSION = "0.11.2"
+  VERSION = "0.11.3"
 end