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

I think you can do all of this in one query:

 Article.published.order('listed ASC, created_at DESC').limit(10)

I may have the sort order wrong on the listed column, but in essence this should work. You'll get any listed items first, sorted by created_at DESC, then non-listed items.

Answer 2

All you need to do is sum the queries:

result1 = Model.where(condition)
result2 = Model.where(another_condition)

# your final result
result = result1 + result2

Answer 3

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
  

Answer 4

with your initial code:

You can join two arrays using + then get first 10 results:

  def self.current
    (Article.listed_articles  +  Article.rescue_articles)[0..9]
  end

I suppose a really dirty way of doing it would be:

  def self.current
      oldest_accepted = Article.published.order('created_at DESC').limit(25).last
      Artcile.published.where(['created_at > ?', oldest_accepted.created_at]).order('listed DESC').limit(10)
  end