Module: AmsLazyRelationships

Defined in:: lib/ams_lazy_relationships/extensions/reflection.rb,
lib/ams_lazy_relationships.rb,
lib/ams_lazy_relationships/loaders.rb,
lib/ams_lazy_relationships/version.rb,
lib/ams_lazy_relationships/extensions.rb,
lib/ams_lazy_relationships/loaders/base.rb,
lib/ams_lazy_relationships/loaders/direct.rb,
lib/ams_lazy_relationships/loaders/association.rb,
lib/ams_lazy_relationships/loaders/simple_has_many.rb,
lib/ams_lazy_relationships/loaders/simple_belongs_to.rb

Overview

There is a general problem inside AMS related to custom association finder combined with ‘include_data` setting:

class BlogPostSerializer < BaseSerializer
  belongs_to :category do
    include_data :if_sideloaded
    object.categories.last
  end
end

The problem is that ‘belongs_to` block will be fully evaluated each time for each object, and only after that AMS is able to take into account `include_data` mode - github.com/rails-api/active_model_serializers/blob/v0.10.10/lib/active_model/serializer/reflection.rb#L162-L163

def value(serializer, include_slice)
  # ...
  block_value = instance_exec(serializer, &block) if block
  return unless include_data?(include_slice)
  # ...
end

That causing redundant (and so huge potentially!) SQL queries and AR objects allocation when ‘include_data` appears to be `false` but `belongs_to` block defines instant (not a kind of AR::Relation) custom association finder.

Described problem is a very specific use case for pure AMS applications. The bad news is that ‘ams_lazy_relationships` always utilizes the association block - github.com/Bajena/ams_lazy_relationships/blob/v0.2.0/lib/ams_lazy_relationships/core/relationship_wrapper_methods.rb#L32-L36

def define_lazy_association(type, name, options, block)

#...
block ||= lambda do |serializer|
  serializer.public_send("lazy_#{name}")
end

public_send(type, name.to_sym, real_relationship_options, &block)
#...

end

This way we break ‘include_data` optimizations for the host application.

In order to overcome that we are forced to monkey-patch ‘AmsLazyRelationships::Extensions::Reflection#value` method and make it to be ready for Proc returned by association block. This way we will use a kind of

block ||= lambda do |serializer|
  -> { serializer.public_send("lazy_#{name}") }
end

as association block, then AMS will evaluate it, get the value of ‘include_data` setting, make a decision do we need to continue with that association, if so - will finally evaluate the proc with lazy relationship inside it.

Defined Under Namespace

Modules: Core, Extensions, Loaders

Constant Summary collapse

VERSION =

"0.4.0"