Class: DeepPreloader::PreloadWorker

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

Instance Method Summary collapse

Constructor Details

#initialize(lock:) ⇒ PreloadWorker

Returns a new instance of PreloadWorker.



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# File 'lib/deep_preloader.rb', line 22

def initialize(lock:)
  @lock     = lock
  @worklist = {}
end

Instance Method Details

#add_associations_from_spec(models, spec) ⇒ Object 



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# File 'lib/deep_preloader.rb', line 27

def add_associations_from_spec(models, spec)
  models = Array.wrap(models)

  # A polymorphic spec expects models of several types, and defines which
  # associations to preload for each of them.
  if spec.polymorphic?
    # We expect models to be of different types, and to have different subspecs for each.
    models_by_class = models.group_by(&:class)

    models_by_class.each do |model_class, class_models|
      model_spec = spec.for_type(model_class)
      next unless model_spec

      add_associations_from_spec(class_models, model_spec)
    end
  else
    # A non-polymorphic spec implies that the models are all of the same type
    model_class = models.first.class

    unless models.all? { |m| m.is_a?(model_class) }
      raise ArgumentError.new('Provided multiple model types to a non-polymorphic preload spec')
    end

    spec.association_specs.each do |association_name, child_spec|
      association_reflection = model_class.reflect_on_association(association_name)
      if association_reflection.nil?
        raise ArgumentError.new("Preloading error: couldn't find association #{association_name} on model class #{model_class.name}")
      end

      # A polymorphic association links to many different model types
      # (discriminated in the referrer), so must be loaded separately per
      # target model type.
      if association_reflection.polymorphic?
        add_polymorphic_association(models, association_reflection, child_spec)
      else
        add_association(models, association_reflection, child_spec)
      end
    end
  end
end

#run! ⇒ Object 



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# File 'lib/deep_preloader.rb', line 68

def run!
  while @worklist.present?
    context, entries = @worklist.shift
    ActiveRecord::Base.logger&.debug("Preloading children in context #{context}") if DEBUG

    loaded_entries, unloaded_entries = entries.partition(&:loaded?)

    unloaded_keys = unloaded_entries.map(&:key).to_set.delete(nil)

    ActiveRecord::Base.logger&.debug("Need to load children for following keys: #{unloaded_keys.to_a}") if DEBUG

    found_children = {}

    if unloaded_keys.present?
      # When :belongs_to, children could be shared with already loaded
      # entries - use what we already have.
      loaded_entries.each do |entry|
        next unless entry.belongs_to?

        if entry.belongs_to? && unloaded_keys.delete?(entry.key)
          found_children[entry.key] = entry.children
        end
      end
      ActiveRecord::Base.logger&.debug("found loaded children for keys #{found_children.keys}") if DEBUG
    end

    if unloaded_keys.present?
      fetched_children = context.load_children(unloaded_keys.to_a, lock: @lock)
      ActiveRecord::Base.logger&.debug("fetched children for keys #{fetched_children.keys}") if DEBUG
      found_children.merge!(fetched_children)
    end

    unloaded_entries.each do |entry|
      children = found_children.fetch(entry.key, [])
      entry.children = children
    end

    entries.each do |entry|
      children = entry.children
      child_spec = entry.child_spec
      next unless child_spec && children.present?

      add_associations_from_spec(children, child_spec)
    end
  end
end