Class: EagerGroup::Preloader

Inherits:
Object
  • Object
show all
Defined in:
lib/eager_group/preloader.rb

Instance Method Summary collapse

Constructor Details

#initialize(klass, records, eager_group_values) ⇒ Preloader

Returns a new instance of Preloader.



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# File 'lib/eager_group/preloader.rb', line 5

def initialize(klass, records, eager_group_values)
  @klass = klass
  @records = Array.wrap(records).compact.uniq
  @eager_group_values = eager_group_values
end

Instance Method Details

#run ⇒ Object

Preload aggregate functions



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# File 'lib/eager_group/preloader.rb', line 12

def run
  primary_key = @klass.primary_key
  @eager_group_values.each do |eager_group_value|
    definition_key, arguments =
      eager_group_value.is_a?(Array) ? [eager_group_value.shift, eager_group_value] : [eager_group_value, nil]

    if definition_key.is_a?(Hash)
      association_name, definition_key = *definition_key.first
      @records = @records.flat_map { |record| record.send(association_name) }
      next if @records.empty?

      @klass = @records.first.class
    end
    record_ids = @records.map { |record| record.send(primary_key) }
    unless definition = @klass.eager_group_definitions[definition_key]
      next
    end

    reflection = @klass.reflect_on_association(definition.association)
    association_class = reflection.klass
    association_class = association_class.instance_exec(*arguments, &definition.scope) if definition.scope

    foreign_key, aggregate_hash =
      if reflection.is_a?(ActiveRecord::Reflection::HasAndBelongsToManyReflection)
        ["#{reflection.join_table}.#{reflection.foreign_key}", @klass.joins(reflection.name)]
      elsif reflection.through_reflection
        ["#{reflection.through_reflection.name}.#{reflection.through_reflection.foreign_key}", @klass.joins(reflection.name)]
      else
        [reflection.foreign_key, association_class]
      end
    aggregate_hash = aggregate_hash.where(foreign_key => record_ids)
                                   .where(polymophic_as_condition(reflection))
                                   .group(foreign_key)
                                   .send(definition.aggregation_function, definition.column_name)
    if definition.need_load_object
      aggregate_objects = reflection.klass.find(aggregate_hash.values).each_with_object({}) { |o, h| h[o.id] = o }
      aggregate_hash.keys.each { |key| aggregate_hash[key] = aggregate_objects[aggregate_hash[key]] }
    end
    @records.each do |record|
      id = record.send(primary_key)
      record.send("#{definition_key}=", aggregate_hash[id] || definition.default_value)
    end
  end
end