```ruby
module Superstore
  module BelongsTo
    class Association
      attr_reader :owner, :reflection
      attr_accessor :record_variable
      delegate :options, to: :reflection

      def initialize(owner, reflection)
        @owner = owner
        @reflection = reflection
      end

      def reader
        unless loaded?
          check_appropriate_primary_key!
          self.record_variable = get_record
          @loaded = true
        end

        record_variable
      end

      def writer(record)
        check_appropriate_primary_key!
        self.record_variable = record
        @loaded = true
        owner.send("#{reflection.foreign_key}=", record.try(reflection.primary_key))
        if reflection.polymorphic?
          owner.send("#{reflection.polymorphic_column}=", record.class.name)
        end
      end

      def association_class
        association_class_name.constantize
      end

      def association_class_name
        reflection.polymorphic? ? owner.send(reflection.polymorphic_column) : reflection.class_name
      end

      def loaded?
        @loaded
      end

      private

      def get_record
        record_id = owner.send(reflection.foreign_key).presence
        return unless record_id

        if reflection.default_primary_key?
          association_class.find_by_id(record_id)
        else
          association_class.where(reflection.primary_key => record_id).first
        end
      end

      def check_appropriate_primary_key!
        if !reflection.default_primary_key? && !(association_class <= ActiveRecord::Base)
          raise ArgumentError, "Association must inherit from ActiveRecord::Base to use custom primary key"
        end
      end
    end
  end
end
```

Use find_by rather than where for belongs_to query
user
```ruby
module Superstore
  module BelongsTo
    class Association
      attr_reader :owner, :reflection
      attr_accessor :record_variable
      delegate :options, to: :reflection

      def initialize(owner, reflection)
        @owner = owner
        @reflection = reflection
      end

      def reader
        unless loaded?
          check_appropriate_primary_key!
          self.record_variable = get_record
          @loaded = true
        end

        record_variable
      end

      def writer(record)
        check_appropriate_primary_key!
        self.record_variable = record
        @loaded = true
        owner.send("#{reflection.foreign_key}=", record.try(reflection.primary_key))
        if reflection.polymorphic?
          owner.send("#{reflection.polymorphic_column}=", record.class.name)
        end
      end

      def association_class
        association_class_name.constantize
      end

      def association_class_name
        reflection.polymorphic? ? owner.send(reflection.polymorphic_column) : reflection.class_name
      end

      def loaded?
        @loaded
      end

      private

      def get_record
        record_id = owner.send(reflection.foreign_key).presence
        return unless record_id

        if reflection.default_primary_key?
          association_class.find_by_id(record_id)
        else
          association_class.find_by(reflection.primary_key => record_id)
        end
      end

      def check_appropriate_primary_key!
        if !reflection.default_primary_key? && !(association_class <= ActiveRecord::Base)
          raise ArgumentError, "Association must inherit from ActiveRecord::Base to use custom primary key"
        end
      end
    end
  end
end
```
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