Query objects for complex ActiveRecord queries

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                  class PopularPostsQuery
  def initialize(relation = Post.all)
    @relation = relation
  end

  def call(timeframe: 7.days, min_views: 100, limit: 20)
    @relation
      .joins(:author)
      .where('posts.created_at >= ?', timeframe.ago)
      .where('posts.views >= ?', min_views)
      .where('users.status = ?', 'active')
      .where(posts: { published_at: ...Time.current })
      .select('posts.*, (posts.views * 0.6 + posts.likes_count * 0.4) AS popularity_score')
      .order('popularity_score DESC')
      .limit(limit)
  end
end

                  module Api
  module V1
    class PostsController < BaseController
      def popular
        posts = PopularPostsQuery.new.call(
          timeframe: params[:timeframe]&.to_i&.days || 7.days,
          min_views: params[:min_views]&.to_i || 100,
          limit: params[:limit]&.to_i || 20
        )

        render json: posts
      end
    end
  end
end

When queries become too complex for scopes—involving multiple joins, subqueries, or raw SQL fragments—I extract them into dedicated query objects. Each query object is a plain Ruby class that encapsulates one specific query pattern and returns an ActiveRecord::Relation so results remain composable. This keeps models lean and makes testing easier since I can verify query logic in isolation. Query objects also improve performance visibility—I can instrument them with logging or metrics to track slow queries. The pattern works particularly well for search and reporting features where query complexity grows over time. I prefer query objects over putting everything in scopes when the logic exceeds 3-4 lines.

Alex Kumar

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Query objects for complex ActiveRecord queries

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