Module: ArLazyPreload::Relation

Defined in:
lib/ar_lazy_preload/active_record/relation.rb

Overview

ActiveRecord::Relation patch with lazy preloading support

Instance Attribute Summary collapse

Instance Method Summary collapse

Instance Attribute Details

#lazy_preload_values ⇒ Object 



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# File 'lib/ar_lazy_preload/active_record/relation.rb', line 79

def lazy_preload_values
  @lazy_preload_values ||= []
end

#preloads_associations_lazily=(value) ⇒ Object (writeonly)

Sets the attribute preloads_associations_lazily



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# File 'lib/ar_lazy_preload/active_record/relation.rb', line 10

def preloads_associations_lazily=(value)
  @preloads_associations_lazily = value
end

Instance Method Details

#lazy_preload(*args) ⇒ Object

Specify relationships to be loaded lazily when association is loaded for the first time. For example:

users = User.lazy_preload(:posts)
users.each do |user|
  user.first_name
end

will cause only one SQL request to load users, while

users = User.lazy_preload(:posts)
users.each do |user|
  user.posts.map(&:id)
end

will make an additional query.



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# File 'lib/ar_lazy_preload/active_record/relation.rb', line 68

def lazy_preload(*args)
  check_if_method_has_arguments!(:lazy_preload, args)
  spawn.lazy_preload!(*args)
end

#lazy_preload!(*args) ⇒ Object 



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# File 'lib/ar_lazy_preload/active_record/relation.rb', line 73

def lazy_preload!(*args)
  args.flatten!
  self.lazy_preload_values += args
  self
end

#load ⇒ Object

Enhanced #load method will check if association has not been loaded yet and add a context for lazy preloading to loaded each record



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# File 'lib/ar_lazy_preload/active_record/relation.rb', line 27

def load
  need_context = !loaded?
  result = super
  if need_context
    Context.register(
      records: ar_lazy_preload_records,
      association_tree: lazy_preload_values,
      auto_preload: preloads_associations_lazily?
    )
  end
  result
end

#preload_associations(records) ⇒ Object 



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# File 'lib/ar_lazy_preload/active_record/relation.rb', line 12

def preload_associations(records)
  preload = preload_values
  preload += includes_values unless eager_loading?
  preloader = nil
  preload.each do |associations|
    preloader ||= build_preloader
    preloader_associations = preloader.preload records, associations
    preloader_associations.each do |preloader_association|
      handle_preloaded_records(preloader_association.preloaded_records)
    end
  end
end

#preload_associations_lazily ⇒ Object

Lazily autoloads all associations. For example:

users = User.preload_associations_lazily
users.each do |user|
  user.posts.flat_map {|post| post.comments.map(&:id)}
end

Same effect can be achieved by User.lazy_preload(posts: :comments)



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# File 'lib/ar_lazy_preload/active_record/relation.rb', line 48

def preload_associations_lazily
  spawn.tap { |relation| relation.preloads_associations_lazily = true }
end