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BufferedMutation breaks after_xxx hooks. #177
Description
Problem
activerecord-spanner-adapter breaks ActiveRecord's after_xxx hooks.
Perhaps this is a problem caused by BufferedMutation.
Like codes shows in bellow, I am unable to retrieve the record in the after_save block immediately after insertion.
I doubt that this similar problem is also happening in after_update and after_create.
Solution(?)
I do not have a idea to monkey-patch for this problem.
My only solution was to remove require "activerecord_spanner_adapter/base" from lib.
Reproduce
sample code:
require "bundler/inline"
gemfile do
source "https://rubygems.org"
git_source(:github) { |repo| "https://github.com/#{repo}.git" }
gem 'activerecord', '6.1.6'
gem 'activerecord-spanner-adapter'
# gem 'activerecord-spanner-adapter',
# git: 'https://github.com/googleapis/ruby-spanner-activerecord',
# ref: '2d30298fd0dedb447ce9ff089df43c65131dc9fe' # composite-pk branch
end
require "active_record"
require "activerecord-spanner-adapter"
require "google/cloud/spanner"
spanner = Google::Cloud::Spanner.new project: "test-project", emulator_host: "localhost:9010"
job = spanner.create_instance "test-instance",
name: "Test Instance",
config: "emulator-config",
nodes: 1
job.wait_until_done!
instance = spanner.instance "test-instance"
job = instance.create_database "testdb", statements: []
job.wait_until_done!
ActiveRecord::Base.establish_connection(project: "test-project", adapter: "spanner", instance: "test-instance", database: "testdb", emulator_host: "localhost:9010")
ActiveRecord::Schema.define do
create_table :singers, force: true, id: false do |t|
t.integer :singer_id, null: false, primary_key: true
t.column :first_name, :string, limit: 200
t.string :last_name
end
end
class Singer < ActiveRecord::Base
after_save do
Singer.print_name
end
def self.print_name
puts "first name => #{Singer.first&.first_name}"
end
end
Singer.create(first_name: "John", last_name: "Doe")
Singer.print_name
singer = Singer.first
singer.first_name = "Jane"
singer.save!output:
-- create_table(:singers, {:force=>true, :id=>false})
-> 0.0135s
first name => <=== can't see created record in after_save
first name => John
first name => Jane
This is expected output by using MySQL or remove require "activerecord_spanner_adapter/base" from lib.
-- create_table(:singers, {:force=>true, :id=>false})
-> 0.0172s
first name => John
first name => John
first name => Jane
Activity
olavloite commentedon Jun 14, 2022
@curi1119 I see now what you are doing, and yes; that is caused by
buffered_mutations. I'm however inclined to say that it is a 'known limitation' of the Spanner adapter. The reason that it does not work is that the code you have in theafter_savemethod tries to re-fetch the record from the database:(The
Singer.firstcall goes to the database to fetch the record)Instead, in this specific example, you could just call
first_nameon the Singer instance that you have in theafter_savemethod. There might be specific use cases where it could make sense to fetch the record from the database, for example if you have a column that is generated by the database. The workaround in that case would be to explicitly use a transaction so the Spanner provider does not use mutations.The reason that the record is not found when you try to query the database in the
after_savemethod is that the transaction has not yet been committed. Mutations are only sent to the database when the transaction is committed. A workaround for your specific example could therefore also be to replace theafter_savecallback with anafter_commitcallback. At that point the record will be available in the database.curi1119 commentedon Jun 16, 2022
@olavloite
Thank you for reply.
Yes, I understand limitation of buffered_mutation and workaround for this problem.
I might use
after_commitortransactionto avoid using buffered_mutation for this problem.(My example is just simplified to show the problem)
My concern is that buffered_mutations changes ActiveRecord's default behavior.
It might be useful to solve avoid limitation of buffered_mutation if there is an implementation like to follow:
activerecord_spanner_adapter/basefrom lib to completely turn off.