Performance on selecting all columns instead of specified attributes

[kevintraver]

Is there a reason the _model_class queries all columns?

jsonapi-resources/lib/jsonapi/active_relation_resource.rb

Lines 286 to 288 in bf4b4cd

	def records_base(_options = {})
	_model_class.all
	end

This is a huge performance impact on models with many columns that may not ever be used by the resource.

It seems for performance reasons it makes sense to only select the attributes defined in the JSONAPI::Resource class.

A workaround for now is to override each resource using .select to retrieve only the fields that are specifically defined.

attributes :name, :address

def self.records(_options = {})
  super.select(self.fields)
end

This should also take into account sparse fieldsets parameters, which would further limit which columns are selected.