adb64db43d
Previously Rails would always remove the connection if it found a matching class in the pool manager. Therefore if `ActiveRecord::Base.establish_connection` was called with the same config, each time it was called it would be clobbered, even though the config hasn't changed and the existing connection is prefectly fine. As far as I can tell from conversations and reading the history this functionality was added for ActiveRecord tests to be able to clobber the connection and use a new config, then re-establish the old connection. Essentially outside Rake tasks and AR tests, this functionality doesn't have a ton of value. On top of not adding a ton of value, this has resulted in a few bugs. In Rails 6.0 I made it so that if you established a connection on `ApplicationRecord` Rails would treat that connection the same as `ActiveRecord::Base.` The reason for this is that the Railtie establishes a connection on boot to the first database, but then if you're using multiple databases you're calling `connects_to` in your `ApplicationRecord` or primary abstract class which essentially doubles your connections to the same database. To avoid opening 2 connections to the same database, Rails treats them the same. However, because we have this code that removes existing connections, when an application boots, `ApplicationRecord` will clobber the connection that the Railtie established even though the connection configs are the same. This removal of the connection caused bugs in migrations that load up a model connected to `ApplicationRecord` (ex `Post.first`) and then calls `execute("SELECT 1")` (obviously a simplified example). When `execute` runs the connection is different from the one opened to run the migration and essentially it is lost when the `remove_connection` code is called. To fix this I've updated the code to only remove the connection if the database config is different. Ultimately I'd like to remove this code altogether but to do that we first need to stop using `Base.establish_connection` in the rake tasks and tests. This will fix the major bugs until I come up with a solution for the areas that currently need to call `establish_connection` on Base. The added benefit of this change is that if your app is calling `establish_connection` multiple times with the same config, it is now 3x faster than the previous implementation because we can return the found pool instead of setting it up again. To benchmark this I duplicated the `establish_connection` method to use the new behavior with a new name. Benchmark script: ```ruby require "active_record" require "logger" require "benchmark/ips" config_hash = { "development" => { "primary" => { "adapter" => "mysql2", "username" => "rails", "database" => "activerecord_unittest"}}} ActiveRecord::Base.configurations = config_hash db_config = ActiveRecord::Base.configurations.configs_for(env_name: "development", name: "primary") p "Same model same config" ActiveRecord::Base.connected_to(role: :writing, prevent_writes: true) do Benchmark.ips do |x| x.report "establish_connection with remove" do ActiveRecord::Base.establish_connection(db_config) end x.report "establish_connection without remove" do ActiveRecord::Base.establish_connection_no_remove(db_config) end x.compare! end end ``` Benchmark results: ``` Warming up -------------------------------------- establish_connection with remove 4.677k i/100ms establish_connection without remove 19.501k i/100ms Calculating ------------------------------------- establish_connection with remove 41.252k (±11.3%) i/s - 205.788k in 5.075525s establish_connection without remove 179.205k (± 6.9%) i/s - 897.046k in 5.029742s Comparison: establish_connection without remove: 179205.1 i/s establish_connection with remove: 41252.3 i/s - 4.34x (± 0.00) slower ``` Other changes: 1) sqlite3 now disconnects and reconnects the connection when `purge` is called. This is necessary now that a new connection isn't created everyt time `establish_connection` is called. Without this change to purge the new database is left in an inaccessible state causing a readonly error from the sqlite3 client. This wasn't happening in mysql or postgres because they were already reconnecting the db connection. 2) I added `remove_connection` to tests that use `ApplicationRecord`. This is required because `ApplicationRecord` or any class that is a `primary_abstract_class` will be treated the same as `ActiveRecord::Base`. This is fine in applications because they are shared connections, but in the AR test environment, we don't want those connnections to stick around (we want AR::Base back). 3) In the async tests I removed 2 calls to `establish_connection`. These were causing sqlite3 tests to leak the state of async_executor because it's stored on the connection. I'm not sure why these were calling `establish_connection` but it's not necessary and was leaking state when now that we are no longer removing the connection. Fixes: #41855 Fixes: #41876 Fixes: #42873 Fixes: #43004 |
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test | ||
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activerecord.gemspec | ||
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MIT-LICENSE | ||
Rakefile | ||
README.rdoc | ||
RUNNING_UNIT_TESTS.rdoc |
= Active Record -- Object-relational mapping in Rails Active Record connects classes to relational database tables to establish an almost zero-configuration persistence layer for applications. The library provides a base class that, when subclassed, sets up a mapping between the new class and an existing table in the database. In the context of an application, these classes are commonly referred to as *models*. Models can also be connected to other models; this is done by defining *associations*. Active Record relies heavily on naming in that it uses class and association names to establish mappings between respective database tables and foreign key columns. Although these mappings can be defined explicitly, it's recommended to follow naming conventions, especially when getting started with the library. You can read more about Active Record in the {Active Record Basics}[https://edgeguides.rubyonrails.org/active_record_basics.html] guide. A short rundown of some of the major features: * Automated mapping between classes and tables, attributes and columns. class Product < ActiveRecord::Base end {Learn more}[link:classes/ActiveRecord/Base.html] The Product class is automatically mapped to the table named "products", which might look like this: CREATE TABLE products ( id bigint NOT NULL auto_increment, name varchar(255), PRIMARY KEY (id) ); This would also define the following accessors: <tt>Product#name</tt> and <tt>Product#name=(new_name)</tt>. * Associations between objects defined by simple class methods. class Firm < ActiveRecord::Base has_many :clients has_one :account belongs_to :conglomerate end {Learn more}[link:classes/ActiveRecord/Associations/ClassMethods.html] * Aggregations of value objects. class Account < ActiveRecord::Base composed_of :balance, class_name: 'Money', mapping: %w(balance amount) composed_of :address, mapping: [%w(address_street street), %w(address_city city)] end {Learn more}[link:classes/ActiveRecord/Aggregations/ClassMethods.html] * Validation rules that can differ for new or existing objects. class Account < ActiveRecord::Base validates :subdomain, :name, :email_address, :password, presence: true validates :subdomain, uniqueness: true validates :terms_of_service, acceptance: true, on: :create validates :password, :email_address, confirmation: true, on: :create end {Learn more}[link:classes/ActiveRecord/Validations.html] * Callbacks available for the entire life cycle (instantiation, saving, destroying, validating, etc.). class Person < ActiveRecord::Base before_destroy :invalidate_payment_plan # the `invalidate_payment_plan` method gets called just before Person#destroy end {Learn more}[link:classes/ActiveRecord/Callbacks.html] * Inheritance hierarchies. class Company < ActiveRecord::Base; end class Firm < Company; end class Client < Company; end class PriorityClient < Client; end {Learn more}[link:classes/ActiveRecord/Base.html] * Transactions. # Database transaction Account.transaction do david.withdrawal(100) mary.deposit(100) end {Learn more}[link:classes/ActiveRecord/Transactions/ClassMethods.html] * Reflections on columns, associations, and aggregations. reflection = Firm.reflect_on_association(:clients) reflection.klass # => Client (class) Firm.columns # Returns an array of column descriptors for the firms table {Learn more}[link:classes/ActiveRecord/Reflection/ClassMethods.html] * Database abstraction through simple adapters. # connect to SQLite3 ActiveRecord::Base.establish_connection(adapter: 'sqlite3', database: 'dbfile.sqlite3') # connect to MySQL with authentication ActiveRecord::Base.establish_connection( adapter: 'mysql2', host: 'localhost', username: 'me', password: 'secret', database: 'activerecord' ) {Learn more}[link:classes/ActiveRecord/Base.html] and read about the built-in support for MySQL[link:classes/ActiveRecord/ConnectionAdapters/Mysql2Adapter.html], PostgreSQL[link:classes/ActiveRecord/ConnectionAdapters/PostgreSQLAdapter.html], and SQLite3[link:classes/ActiveRecord/ConnectionAdapters/SQLite3Adapter.html]. * Logging support for Log4r[https://github.com/colbygk/log4r] and Logger[https://ruby-doc.org/stdlib/libdoc/logger/rdoc/]. ActiveRecord::Base.logger = ActiveSupport::Logger.new(STDOUT) ActiveRecord::Base.logger = Log4r::Logger.new('Application Log') * Database agnostic schema management with Migrations. class AddSystemSettings < ActiveRecord::Migration[7.1] def up create_table :system_settings do |t| t.string :name t.string :label t.text :value t.string :type t.integer :position end SystemSetting.create name: 'notice', label: 'Use notice?', value: 1 end def down drop_table :system_settings end end {Learn more}[link:classes/ActiveRecord/Migration.html] == Philosophy Active Record is an implementation of the object-relational mapping (ORM) pattern[https://www.martinfowler.com/eaaCatalog/activeRecord.html] by the same name described by Martin Fowler: "An object that wraps a row in a database table or view, encapsulates the database access, and adds domain logic on that data." Active Record attempts to provide a coherent wrapper as a solution for the inconvenience that is object-relational mapping. The prime directive for this mapping has been to minimize the amount of code needed to build a real-world domain model. This is made possible by relying on a number of conventions that make it easy for Active Record to infer complex relations and structures from a minimal amount of explicit direction. Convention over Configuration: * No XML files! * Lots of reflection and run-time extension * Magic is not inherently a bad word Admit the Database: * Lets you drop down to SQL for odd cases and performance * Doesn't attempt to duplicate or replace data definitions == Download and installation The latest version of Active Record can be installed with RubyGems: $ gem install activerecord Source code can be downloaded as part of the Rails project on GitHub: * https://github.com/rails/rails/tree/main/activerecord == License Active Record is released under the MIT license: * https://opensource.org/licenses/MIT == Support API documentation is at: * https://api.rubyonrails.org Bug reports for the Ruby on Rails project can be filed here: * https://github.com/rails/rails/issues Feature requests should be discussed on the rails-core mailing list here: * https://discuss.rubyonrails.org/c/rubyonrails-core