How do I combine results from two queries on the same model?

Question

I need to return exactly ten records for use in a view. I have a highly restrictive query I\'d like to use, but I want a less restrictive query in place to fill in the results i

Answer 1

If you want an ActiveRecord::Relation object instead of an Array, you can use:

• ActiveRecordUnion gem.

  Install gem: gem install active_record_union and use:

  def self.current
    Article.rescue_articles.union(Article.listed_articles).limit(10)
  end
  

• UnionScope module.

  Create module UnionScope (lib/active_record/union_scope.rb).

  module ActiveRecord::UnionScope
    def self.included(base)
      base.send :extend, ClassMethods
    end
  
    module ClassMethods
      def union_scope(*scopes)
        id_column = "#{table_name}.id"
         if (sub_query = scopes.reject { |sc| sc.count == 0 }.map { |s|   "(#{s.select(id_column).to_sql})" }.join(" UNION ")).present?
          where "#{id_column} IN (#{sub_query})"
        else
          none
        end
      end
    end
  end
  

  Then call it in your Article model.

  class Article < ActiveRecord::Base
    include ActiveRecord::UnionScope
    ...
    def self.current
      union_scope(Article.rescue_articles, Article.listed_articles).limit(10)
    end
    ...
  end