methods for debugging slow queries in active model serializers? - ruby-on-rails

Question

I am having difficulty optimizing my Active Model Serializers to avoid the n+1 problem. As per suggestions from their docs, I have attempted to eager load the associations which i thought were causing my query bottlenecks, but my serializers are still taking forever.
Obviously, i must be doing something wrong. My application is deeply nested with associations, so i guess I'm more interested in discovering a tool to unveil to me exactly WHICH associations are costing me. Right now, i am attaching a stack trace to every query run through the ActiveRecord
ActiveSupport::Notifications.subscribe("sql.active_record") do |_, _, _, _, details|
puts caller.join("\n")
puts "*" * 50
end
which gives me a ridiculous output because i am running so many queries to begin with, but, in addition, the stack traces are not helpful at identifying which serializer is at fault. It shows me which controller method was calling render, but then from there the stack trace simply prints methods from gems/active_model_serializers, which does not help me.
I am hoping to uncover a method of debugging that would be able to identify to me which serializers were at fault, that way i am not guessing at how to optimize my queries. Has anybody discovered anything like this? Thanks!
===================
UPDATE
Just so it is clear, i am already printing a query log, in addition to a stack trace. Unfortunately, with so many associations to keep track of, the query log is not exactly helpful at identifying the source of the query. It is guess work at best, and ineffective at the association scope i am dealing with.
I have abandoned the stack traces altogether, finding them to be totally unhelpful. Now, all i have printing are SQL logs, and i am manually sifting through them, trying to discover the source of the association.
The next method I will attempt (although i hate to resort to it) is commenting out associations until i see improvements in my query times. It will be more effective than trying to trace the source of the problem, but it will provide me no comfort in a production environment (where commenting out critical associations is not an option), so if anybody finds a solution that can help, I would still be very grateful.
I will continue to post updates as I move through this problem, as it may help many others in the future.
======================UPDATE 2
It turns out that commenting out associations in my serializer and reintroducing them one at a time, while ineffective in production, is an excellent way to debug in a local environment. I was able to drill down to the problem within a minute and correct it. Still, this is not an ideal solution. I would ideally like to be able to identify the problem from a log so that in production i could ascertain the issue without affecting the application's behavior.

Answer 1

The active_record_query_trace gem can do that.
Add the following to your Gemfile:
group :development do
gem 'active_record_query_trace'
end
Create an initializer such as config/initializers/active_record_query_trace.rb to enable the gem. If you want to customize how the gem behaves, you can add any combination of the options described in the docs to the initializer as well.
if Rails.env.development?
ActiveRecordQueryTrace.enabled = true
# Optional: other gem config options go here
end
Restart the Rails development server.

Answer 2

Easy way within any gems - is logging each string of code. For example, if you have
that code of serializer:
module Flats
class IndexSerializer < Api::V2::RealtyObjects::IndexSerializer
attributes(
:flat_number,
:entrance_number,
:floor_in_house,
:live_area,
:room_count,
:total_area,
)
end
end
add method which will be log time to your development.log on each attribute:
module Flats
class IndexSerializer < Api::V2::RealtyObjects::IndexSerializer
attribute_list = %i[
flat_number
entrance_number
floor_in_house
live_area
room_count
total_area
]
attributes(*attribute_list)
def logger(name, value)
Rails.logger.debug name, value, "#{Time.now.strftime('%M:%S--%N')}"
end
attribute_list.each do |attribute_name|
define_method attribute_name do |value|
logger(attribute_name, value)
super
end
end
end
end