Module: Ar::Preloader

Defined in:
lib/ar/preloader.rb,
lib/ar/preloader/version.rb

Defined Under Namespace

Classes: Error

Constant Summary collapse

VERSION = 
"1.1.0"

Class Method Summary collapse

Class Method Details

.check_association_exists(klass, association) ⇒ Object 



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# File 'lib/ar/preloader.rb', line 8

def self.check_association_exists(klass, association)
  case association
  when String, Symbol
    return klass.reflections.keys.include?(association.to_s)
  when Array
    association.each do |v|
      return false unless Ar::Preloader.check_association_exists(klass, v)
    end
  when Hash
    association.each_pair do |k,v|
      return false unless klass.reflections.keys.include?(k.to_s)

      associated_klass = klass.reflections[k.to_s].class_name.constantize

      case v
      when String, Symbol, Hash
        return false unless Ar::Preloader.check_association_exists(associated_klass, v)
      when Array
        v.each do |each_v|
          return false unless Ar::Preloader.check_association_exists(associated_klass, each_v)
        end
      else
      end
    end

    return true
  else
    return false
  end
end

.preload_association(list, association, inner_associations = []) ⇒ Object 



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# File 'lib/ar/preloader.rb', line 39

def self.preload_association(list, association, inner_associations = [])
  return if list.length == 0

  case association
  when String, Symbol
    klass = list.first.class
    klass.send :attr_reader, "_#{association}".to_sym

    association_details = klass.reflections[association.to_s]
    association_klass = association_details.class_name.constantize

    case association_details
    when ActiveRecord::Reflection::HasManyReflection
      foreign_key = association_details.foreign_key
      association_pk = association_klass.primary_key

      list.each do |obj|
        instance_variable_name = "@_#{association}".to_sym
        obj.instance_variable_set(instance_variable_name, [])
      end

      query = <<-EOS
SELECT
  distinct #{association_klass.table_name}.*
FROM #{association_klass.table_name}
WHERE #{association_klass.table_name}.#{foreign_key} in (#{ list.map{ |e| e[klass.primary_key.to_sym].try(:to_s) }.compact.join(",") })

EOS

      association_list = association_klass.find_by_sql(query).to_a

      if inner_associations.is_a?(Array)
        association_list.preload(*inner_associations)
      else
        association_list.preload(inner_associations)
      end

      list.each do |obj|
        instance_variable_name = "@_#{association}".to_sym

        association_list.select{ |e| e[foreign_key.to_sym] == obj[klass.primary_key.to_sym] }.each do |association_obj|
          each_list = obj.instance_variable_get(instance_variable_name)
          each_list << association_obj
          obj.instance_variable_set(instance_variable_name, each_list)
        end
      end
    when ActiveRecord::Reflection::BelongsToReflection
      foreign_key = association_details.foreign_key
      association_pk = association_klass.primary_key

      if list.map{ |e| e[foreign_key.to_sym] }.compact.length == 0
        return true
      end

      query = <<-EOS
SELECT
  distinct #{association_klass.table_name}.*
FROM #{association_klass.table_name}
WHERE #{association_klass.table_name}.#{association_klass.primary_key} in (#{ list.map{ |e| e[foreign_key.to_sym].try(:to_s) }.compact.join(",") })

EOS

      association_list = association_klass.find_by_sql(query).to_a

      if inner_associations.is_a?(Array)
        association_list.preload(*inner_associations)
      else
        association_list.preload(inner_associations)
      end

      association_map = association_list.map{ |e| [e[e.class.primary_key.to_sym], e] }.to_h

      list.each do |obj|
        if obj[foreign_key.to_sym].present? && association_map[obj[foreign_key.to_sym]].present?
          obj.instance_variable_set( "@_#{association}".to_sym, association_map[obj[foreign_key.to_sym]] )
        end
      end
    when ActiveRecord::Reflection::HasAndBelongsToManyReflection
      foreign_key = association_details.foreign_key
      association_foreign_key = association_details.association_foreign_key
      join_table = association_details.join_table

      list.each do |obj|
        instance_variable_name = "@_#{association}".to_sym
        obj.instance_variable_set(instance_variable_name, [])
      end

      join_query = <<-EOS
SELECT
  #{join_table}.#{foreign_key},
  #{join_table}.#{association_foreign_key}
FROM #{join_table}
WHERE #{join_table}.#{foreign_key} IN (#{ list.map{ |e| e[klass.primary_key.to_sym].try(:to_s) }.compact.join(",") })

EOS
      join_entries = ActiveRecord::Base.connection.execute(join_query).to_a

      query = <<-EOS
SELECT
  distinct #{association_klass.table_name}.*
FROM #{association_klass.table_name}
INNER JOIN #{join_table} ON #{join_table}.#{association_foreign_key} = #{association_klass.table_name}.#{association_klass.primary_key}
WHERE #{join_table}.#{foreign_key} IN (#{ list.map{ |e| e[klass.primary_key.to_sym].try(:to_s) }.compact.join(",") })

EOS

      association_list = association_klass.find_by_sql(query).to_a

      if inner_associations.is_a?(Array)
        association_list.preload(*inner_associations)
      else
        association_list.preload(inner_associations)
      end

      list.each do |obj|
        instance_variable_name = "@_#{association}".to_sym

        association_key_list = join_entries.select{ |e| e[0] == obj[klass.primary_key.to_s] }.map(&:last)

        association_list.select{ |e| association_key_list.include?( e[association_klass.primary_key.to_s] ) }.each do |association_obj|
          each_list = obj.instance_variable_get(instance_variable_name)
          each_list << association_obj
          obj.instance_variable_set(instance_variable_name, each_list)
        end
      end
    else
      raise Ar::Preloader::Error.new("Unsupported association type: '#{association}'")
    end
  when Hash
    association.each_pair do |k,v|
      Ar::Preloader.preload_association(list, k, v)
    end
  end
end