rails--rails/activerecord/CHANGELOG.md

• Add support for setting the filename of the schema or structure dump in the database config.

  Applications may now set their the filename or path of the schema / structure dump file in their database configuration.

  production:
    primary:
      database: my_db
      schema_dump: my_schema_dump_filename.rb
    animals:
      database: animals_db
      schema_dump: false
  

  The filename set in schema_dump will be used by the application. If set to false the schema will not be dumped. The database tasks are responsible for adding the database directory to the filename. If a full path is provided, the Rails tasks will use that instead of ActiveRecord::DatabaseTasks.db_dir.

  Eileen M. Uchitelle, Ryan Kerr

• Add ActiveRecord::Base.prohibit_shard_swapping to prevent attempts to change the shard within a block.

  John Crepezzi, Eileen M. Uchitelle

• Filter unchanged attributes with default function from insert query when partial_inserts is disabled.

  Akshay Birajdar, Jacopo Beschi

• Add support for FILTER clause (SQL:2003) to Arel.

  Currently supported by PostgreSQL 9.4+ and SQLite 3.30+.

  Andrey Novikov

• Automatically set timestamps on record creation during bulk insert/upsert

  Prior to this change, only updates during an upsert operation (e.g. upsert_all) would touch timestamps (updated_{at,on}). Now, record creations also touch timestamp columns ({created,updated}_{at,on}).

  This behaviour is controlled by the <model>.record_timestamps config, matching the behaviour of create, update, etc. It can also be overridden by using the record_timestamps: keyword argument.

  Note that this means upsert_all on models with record_timestamps = false will no longer touch updated_{at,on} automatically.

  Sam Bostock

• Don't require role when passing shard to connected_to.

  connected_to can now be called with a shard only. Note that role is still inherited if connected_to calls are nested.

  Eileen M. Uchitelle

• Add option to lazily load the schema cache on the connection.

  Previously, the only way to load the schema cache in Active Record was through the Railtie on boot. This option provides the ability to load the schema cache on the connection after it's been established. Loading the cache lazily on the connection can be beneficial for Rails applications that use multiple databases because it will load the cache at the time the connection is established. Currently Railties doesn't have access to the connections before boot.

  To use the cache, set config.active_record.lazily_load_schema_cache = true in your application configuration. In addition a schema_cache_path should be set in your database configuration if you don't want to use the default "db/schema_cache.yml" path.

  Eileen M. Uchitelle

• Allow automatic inverse_of detection for associations with scopes.

  Automatic inverse_of detection now works for associations with scopes. For example, the comments association here now automatically detects inverse_of: :post, so we don't need to pass that option:

  class Post < ActiveRecord::Base
    has_many :comments, -> { visible }
  end
  
  class Comment < ActiveRecord::Base
    belongs_to :post
  end
  

  Note that the automatic detection still won't work if the inverse association has a scope. In this example a scope on the post association would still prevent Rails from finding the inverse for the comments association.

  This will be the default for new apps in Rails 7. To opt in:

  config.active_record.automatic_scope_inversing = true
  

  Daniel Colson, Chris Bloom

• Accept optional transaction args to ActiveRecord::Locking::Pessimistic#with_lock

  #with_lock now accepts transaction options like requires_new:, isolation:, and joinable:

• Adds support for deferrable foreign key constraints in PostgreSQL.

  By default, foreign key constraints in PostgreSQL are checked after each statement. This works for most use cases, but becomes a major limitation when creating related records before the parent record is inserted into the database. One example of this is looking up / creating a person via one or more unique alias.

  Person.transaction do
    alias = Alias
      .create_with(user_id: SecureRandom.uuid)
      .create_or_find_by(name: "DHH")
  
    person = Person
      .create_with(name: "David Heinemeier Hansson")
      .create_or_find_by(id: alias.user_id)
  end
  

  Using the default behavior, the transaction would fail when executing the first INSERT statement.

  By passing the :deferrable option to the add_foreign_key statement in migrations, it's possible to defer this check.

  add_foreign_key :aliases, :person, deferrable: true
  

  Passing deferrable: true doesn't change the default behavior, but allows manually deferring the check using SET CONSTRAINTS ALL DEFERRED within a transaction. This will cause the foreign keys to be checked after the transaction.

  It's also possible to adjust the default behavior from an immediate check (after the statement), to a deferred check (after the transaction):

  add_foreign_key :aliases, :person, deferrable: :deferred
  

  Benedikt Deicke

• Allow configuring Postgres password through the socket URL.

  For example:

  ActiveRecord::DatabaseConfigurations::UrlConfig.new(
    :production, :production, 'postgres:///?user=user&password=secret&dbname=app', {}
  ).configuration_hash
  

  will now return,

  { :user=>"user", :password=>"secret", :dbname=>"app", :adapter=>"postgresql" }
  

  Abeid Ahmed

• PostgreSQL: support custom enum types

  In migrations, use create_enum to add a new enum type, and t.enum to add a column.

  def up
    create_enum :mood, ["happy", "sad"]
  
    change_table :cats do |t|
      t.enum :current_mood, enum_type: "mood", default: "happy", null: false
    end
  end
  

  Enums will be presented correctly in schema.rb. Note that this is only supported by the PostgreSQL adapter.

  Alex Ghiculescu

• Avoid COMMENT statements in PostgreSQL structure dumps

  COMMENT statements are now omitted from the output of db:structure:dump when using PostgreSQL >= 11. This allows loading the dump without a pgsql superuser account.

  Fixes #36816, #43107.

  Janosch Müller

• Add support for generated columns in PostgreSQL adapter

  Generated columns are supported since version 12.0 of PostgreSQL. This adds support of those to the PostgreSQL adapter.

  create_table :users do |t|
    t.string :name
    t.virtual :name_upcased, type: :string, as: 'upper(name)', stored: true
  end
  

  Michał Begejowicz

Rails 7.0.0.alpha2 (September 15, 2021)

• No changes.

Rails 7.0.0.alpha1 (September 15, 2021)

• Remove warning when overwriting existing scopes

  Removes the following unnecessary warning message that appeared when overwriting existing scopes

  Creating scope :my_scope_name. Overwriting existing method "MyClass.my_scope_name" when overwriting existing scopes
  

  Weston Ganger

• Use full precision for updated_at in insert_all/upsert_all

  CURRENT_TIMESTAMP provides differing precision depending on the database, and not all databases support explicitly specifying additional precision.

  Instead, we delegate to the new connection.high_precision_current_timestamp for the SQL to produce a high precision timestamp on the current database.

  Fixes #42992

  Sam Bostock

• Add ssl support for postgresql database tasks

  Add PGSSLMODE, PGSSLCERT, PGSSLKEY and PGSSLROOTCERT to pg_env from database config when running postgresql database tasks.

  # config/database.yml
  
  production:
    sslmode: verify-full
    sslcert: client.crt
    sslkey: client.key
    sslrootcert: ca.crt
  

  Environment variables

  PGSSLMODE=verify-full
  PGSSLCERT=client.crt
  PGSSLKEY=client.key
  PGSSLROOTCERT=ca.crt
  

  Fixes #42994

  Michael Bayucot

• Avoid scoping update callbacks in ActiveRecord::Relation#update!.

  Making it consistent with how scoping is applied only to the query in ActiveRecord::Relation#update and not also to the callbacks from the update itself.

  Dylan Thacker-Smith

• Fix 2 cases that inferred polymorphic class from the association's foreign_type using String#constantize instead of the model's polymorphic_class_for.

  When updating a polymorphic association, the old foreign_type was not inferred correctly when:

  1. touching the previously associated record
  2. updating the previously associated record's counter_cache

  Jimmy Bourassa

• Add config option for ignoring tables when dumping the schema cache.

  Applications can now be configured to ignore certain tables when dumping the schema cache.

  The configuration option can table an array of tables:

  config.active_record.schema_cache_ignored_tables = ["ignored_table", "another_ignored_table"]
  

  Or a regex:

  config.active_record.schema_cache_ignored_tables = [/^_/]
  

  Eileen M. Uchitelle

• Make schema cache methods return consistent results.

  Previously the schema cache methods primary_keys, columns, columns_hash, and indexes would behave differently than one another when a table didn't exist and differently across database adapters. This change unifies the behavior so each method behaves the same regardless of adapter.

  The behavior now is:

  columns: (unchanged) raises a db error if the table does not exist. columns_hash: (unchanged) raises a db error if the table does not exist. primary_keys: (unchanged) returns nil if the table does not exist. indexes: (changed for mysql2) returns [] if the table does not exist.

  Eileen M. Uchitelle

• Reestablish connection to previous database after after running db:schema:load:name

  After running db:schema:load:name the previous connection is restored.

  Jacopo Beschi

• Add database config option database_tasks

  If you would like to connect to an external database without any database management tasks such as schema management, migrations, seeds, etc. you can set the per database config option database_tasks: false

  # config/database.yml
  
  production:
    primary:
      database: my_database
      adapter: mysql2
    animals:
      database: my_animals_database
      adapter: mysql2
      database_tasks: false
  

  Weston Ganger

• Fix ActiveRecord::InternalMetadata to not be broken by config.active_record.record_timestamps = false

  Since the model always create the timestamp columns, it has to set them, otherwise it breaks various DB management tasks.

  Fixes #42983

• Add ActiveRecord::QueryLogs.

  Configurable tags can be automatically added to all SQL queries generated by Active Record.

  # config/application.rb
  module MyApp
    class Application < Rails::Application
      config.active_record.query_log_tags_enabled = true
    end
  end
  

  By default the application, controller and action details are added to the query tags:

  class BooksController < ApplicationController
    def index
      @books = Book.all
    end
  end
  

  GET /books
  # SELECT * FROM books /*application:MyApp;controller:books;action:index*/
  

  Custom tags containing static values and Procs can be defined in the application configuration:

  config.active_record.query_log_tags = [
    :application,
    :controller,
    :action,
    {
      custom_static: "foo",
      custom_dynamic: -> { Time.now }
    }
  ]
  

  Keeran Raj Hawoldar, Eileen M. Uchitelle, Kasper Timm Hansen

• Added support for multiple databases to rails db:setup and rails db:reset.

  Ryan Hall

• Add ActiveRecord::Relation#structurally_compatible?.

  Adds a query method by which a user can tell if the relation that they're about to use for #or or #and is structurally compatible with the receiver.

  Kevin Newton

• Add ActiveRecord::QueryMethods#in_order_of.

  This allows you to specify an explicit order that you'd like records returned in based on a SQL expression. By default, this will be accomplished using a case statement, as in:

  Post.in_order_of(:id, [3, 5, 1])
  

  will generate the SQL:

  SELECT "posts".* FROM "posts" ORDER BY CASE "posts"."id" WHEN 3 THEN 1 WHEN 5 THEN 2 WHEN 1 THEN 3 ELSE 4 END ASC
  

  However, because this functionality is built into MySQL in the form of the FIELD function, that connection adapter will generate the following SQL instead:

  SELECT "posts".* FROM "posts" ORDER BY FIELD("posts"."id", 1, 5, 3) DESC
  

  Kevin Newton

• Fix eager_loading? when ordering with Symbol.

  eager_loading? is triggered correctly when using order with symbols.

  scope = Post.includes(:comments).order(:"comments.label")
  => true
  

  Jacopo Beschi

• Two change tracking methods are added for belongs_to associations.

  The association_changed? method (assuming an association named :association) returns true if a different associated object has been assigned and the foreign key will be updated in the next save.

  The association_previously_changed? method returns true if the previous save updated the association to reference a different associated object.

  George Claghorn

• Add option to disable schema dump per-database.

  Dumping the schema is on by default for all databases in an application. To turn it off for a specific database, use the schema_dump option:

  # config/database.yml
  
  production:
    schema_dump: false
  

  Luis Vasconcellos, Eileen M. Uchitelle

• Fix eager_loading? when ordering with Hash syntax.

  eager_loading? is triggered correctly when using order with hash syntax on an outer table.

  Post.includes(:comments).order({ "comments.label": :ASC }).eager_loading?
  # => true
  

  Jacopo Beschi

• Move the forcing of clear text encoding to the ActiveRecord::Encryption::Encryptor.

  Fixes #42699.

  J Smith

• partial_inserts is now disabled by default in new apps.

  This will be the default for new apps in Rails 7. To opt in:

  config.active_record.partial_inserts = true
  

  If a migration removes the default value of a column, this option would cause old processes to no longer be able to create new records.

  If you need to remove a column, you should first use ignored_columns to stop using it.

  Jean Boussier

• Rails can now verify foreign keys after loading fixtures in tests.

  This will be the default for new apps in Rails 7. To opt in:

  config.active_record.verify_foreign_keys_for_fixtures = true
  

  Tests will not run if there is a foreign key constraint violation in your fixture data.

  The feature is supported by SQLite and PostgreSQL, other adapters can also add support for it.

  Alex Ghiculescu

• Clear cached has_one association after setting belongs_to association to nil.

  After setting a belongs_to relation to nil and updating an unrelated attribute on the owner, the owner should still return nil on the has_one relation.

  Fixes #42597.

  Michiel de Mare

• OpenSSL constants are now used for Digest computations.

  Dirkjan Bussink

• Adds support for if_not_exists to add_foreign_key and if_exists to remove_foreign_key.

  Applications can set their migrations to ignore exceptions raised when adding a foreign key that already exists or when removing a foreign key that does not exist.

  Example Usage:

  class AddAuthorsForeignKeyToArticles < ActiveRecord::Migration[7.0]
    def change
      add_foreign_key :articles, :authors, if_not_exists: true
    end
  end
  

  class RemoveAuthorsForeignKeyFromArticles < ActiveRecord::Migration[7.0]
    def change
      remove_foreign_key :articles, :authors, if_exists: true
    end
  end
  

  Roberto Miranda

• Prevent polluting ENV during postgresql structure dump/load.

  Some configuration parameters were provided to pg_dump / psql via environment variables which persisted beyond the command being run, and may have caused subsequent commands and connections to fail. Tasks running across multiple postgresql databases like rails db:test:prepare may have been affected.

  Samuel Cochran

• Set precision 6 by default for datetime columns.

  By default, datetime columns will have microseconds precision instead of seconds precision.

  Roberto Miranda

• Allow preloading of associations with instance dependent scopes.

  John Hawthorn, John Crepezzi, Adam Hess, Eileen M. Uchitelle, Dinah Shi

• Do not try to rollback transactions that failed due to a ActiveRecord::TransactionRollbackError.

  Jamie McCarthy

• Active Record Encryption will now encode values as UTF-8 when using deterministic encryption. The encoding is part of the encrypted payload, so different encodings for different values result in different ciphertexts. This can break unique constraints and queries.

  The new behavior is configurable via active_record.encryption.forced_encoding_for_deterministic_encryption that is Encoding::UTF_8 by default. It can be disabled by setting it to nil.

  Jorge Manrubia

• The MySQL adapter now cast numbers and booleans bind parameters to string for safety reasons.

  When comparing a string and a number in a query, MySQL converts the string to a number. So for instance "foo" = 0, will implicitly cast "foo" to 0 and will evaluate to TRUE which can lead to security vulnerabilities.

  Active Record already protect against that vulnerability when it knows the type of the column being compared, however until now it was still vulnerable when using bind parameters:

  User.where("login_token = ?", 0).first
  

  Would perform:

  SELECT * FROM `users` WHERE `login_token` = 0 LIMIT 1;
  

  Now it will perform:

  SELECT * FROM `users` WHERE `login_token` = '0' LIMIT 1;
  

  Jean Boussier

• Fixture configurations (_fixture) are now strictly validated.

  If an error will be raised if that entry contains unknown keys while previously it would silently have no effects.

  Jean Boussier

• Add ActiveRecord::Base.update! that works like ActiveRecord::Base.update but raises exceptions.

  This allows for the same behavior as the instance method #update! at a class level.

  Person.update!(:all, state: "confirmed")
  

  Dorian Marié

• Add ActiveRecord::Base#attributes_for_database.

  Returns attributes with values for assignment to the database.

  Chris Salzberg

• Use an empty query to check if the PostgreSQL connection is still active.

  An empty query is faster than SELECT 1.

  Heinrich Lee Yu

• Add ActiveRecord::Base#previously_persisted?.

  Returns true if the object has been previously persisted but now it has been deleted.

• Deprecate partial_writes in favor of partial_inserts and partial_updates.

  This allows to have a different behavior on update and create.

  Jean Boussier

• Fix compatibility with psych >= 4.

  Starting in Psych 4.0.0 YAML.load behaves like YAML.safe_load. To preserve compatibility, Active Record's schema cache loader and YAMLColumn now uses YAML.unsafe_load if available.

  Jean Boussier

• ActiveRecord::Base.logger is now a class_attribute.

  This means it can no longer be accessed directly through @@logger, and that setting logger = on a subclass won't change the parent's logger.

  Jean Boussier

• Add .asc.nulls_first for all databases. Unfortunately MySQL still doesn't like nulls_last.

  Keenan Brock

• Improve performance of one? and many? by limiting the generated count query to 2 results.

  Gonzalo Riestra

• Don't check type when using if_not_exists on add_column.

  Previously, if a migration called add_column with the if_not_exists option set to true the column_exists? check would look for a column with the same name and type as the migration.

  Recently it was discovered that the type passed to the migration is not always the same type as the column after migration. For example a column set to :mediumblob in the migration will be casted to binary when calling column.type. Since there is no straightforward way to cast the type to the database type without running the migration, we opted to drop the type check from add_column. This means that migrations adding a duplicate column with a different type will no longer raise an error.

  Eileen M. Uchitelle

• Log a warning message when running SQLite in production.

  Using SQLite in production ENV is generally discouraged. SQLite is also the default adapter in a new Rails application. For the above reasons log a warning message when running SQLite in production.

  The warning can be disabled by setting config.active_record.sqlite3_production_warning=false.

  Jacopo Beschi

• Add option to disable joins for has_one associations.

  In a multiple database application, associations can't join across databases. When set, this option instructs Rails to generate 2 or more queries rather than generating joins for has_one associations.

  Set the option on a has one through association:

  class Person
    has_one :dog
    has_one :veterinarian, through: :dog, disable_joins: true
  end
  

  Then instead of generating join SQL, two queries are used for @person.veterinarian:

  SELECT "dogs"."id" FROM "dogs" WHERE "dogs"."person_id" = ?  [["person_id", 1]]
  SELECT "veterinarians".* FROM "veterinarians" WHERE "veterinarians"."dog_id" = ?  [["dog_id", 1]]
  

  Sarah Vessels, Eileen M. Uchitelle

• Arel::Visitors::Dot now renders a complete set of properties when visiting Arel::Nodes::SelectCore, SelectStatement, InsertStatement, UpdateStatement, and DeleteStatement, which fixes #42026. Previously, some properties were omitted.

  Mike Dalessio

• Arel::Visitors::Dot now supports Arel::Nodes::Bin, Case, CurrentRow, Distinct, DistinctOn, Else, Except, InfixOperation, Intersect, Lock, NotRegexp, Quoted, Regexp, UnaryOperation, Union, UnionAll, When, and With. Previously, these node types caused an exception to be raised by Arel::Visitors::Dot#accept.

  Mike Dalessio

• Optimize remove_columns to use a single SQL statement.

  remove_columns :my_table, :col_one, :col_two
  

  Now results in the following SQL:

  ALTER TABLE "my_table" DROP COLUMN "col_one", DROP COLUMN "col_two"
  

  Jon Dufresne

• Ensure has_one autosave association callbacks get called once.

  Change the has_one autosave callback to be non cyclic as well. By doing this the autosave callback are made more consistent for all 3 cases: has_many, has_one, and belongs_to.

  Petrik de Heus

• Add option to disable joins for associations.

  In a multiple database application, associations can't join across databases. When set, this option instructs Rails to generate 2 or more queries rather than generating joins for associations.

  Set the option on a has many through association:

  class Dog
    has_many :treats, through: :humans, disable_joins: true
    has_many :humans
  end
  

  Then instead of generating join SQL, two queries are used for @dog.treats:

  SELECT "humans"."id" FROM "humans" WHERE "humans"."dog_id" = ?  [["dog_id", 1]]
  SELECT "treats".* FROM "treats" WHERE "treats"."human_id" IN (?, ?, ?)  [["human_id", 1], ["human_id", 2], ["human_id", 3]]
  

  Eileen M. Uchitelle, Aaron Patterson, Lee Quarella

• Add setting for enumerating column names in SELECT statements.

  Adding a column to a PostgreSQL database, for example, while the application is running can change the result of wildcard SELECT * queries, which invalidates the result of cached prepared statements and raises a PreparedStatementCacheExpired error.

  When enabled, Active Record will avoid wildcards and always include column names in SELECT queries, which will return consistent results and avoid prepared statement errors.

  Before:

  Book.limit(5)
  # SELECT * FROM books LIMIT 5
  

  After:

  # config/application.rb
  module MyApp
    class Application < Rails::Application
      config.active_record.enumerate_columns_in_select_statements = true
    end
  end
  
  # or, configure per-model
  class Book < ApplicationRecord
    self.enumerate_columns_in_select_statements = true
  end
  

  Book.limit(5)
  # SELECT id, author_id, name, format, status, language, etc FROM books LIMIT 5
  

  Matt Duszynski

• Allow passing SQL as on_duplicate value to #upsert_all to make it possible to use raw SQL to update columns on conflict:

  Book.upsert_all(
    [{ id: 1, status: 1 }, { id: 2, status: 1 }],
    on_duplicate: Arel.sql("status = GREATEST(books.status, EXCLUDED.status)")
  )
  

  Vladimir Dementyev

• Allow passing SQL as returning statement to #upsert_all:

  Article.insert_all(
    [
      { title: "Article 1", slug: "article-1", published: false },
      { title: "Article 2", slug: "article-2", published: false }
    ],
    returning: Arel.sql("id, (xmax = '0') as inserted, name as new_name")
  )
  

  Vladimir Dementyev

• Deprecate legacy_connection_handling.

  Eileen M. Uchitelle

• Add attribute encryption support.

  Encrypted attributes are declared at the model level. These are regular Active Record attributes backed by a column with the same name. The system will transparently encrypt these attributes before saving them into the database and will decrypt them when retrieving their values.

  class Person < ApplicationRecord
    encrypts :name
    encrypts :email_address, deterministic: true
  end
  

  You can learn more in the Active Record Encryption guide.

  Jorge Manrubia

• Changed Arel predications contains and overlaps to use quoted_node so that PostgreSQL arrays are quoted properly.

  Bradley Priest

• Add mode argument to record level strict_loading!.

  This argument can be used when enabling strict loading for a single record to specify that we only want to raise on n plus one queries.

  developer.strict_loading!(mode: :n_plus_one_only)
  
  developer.projects.to_a # Does not raise
  developer.projects.first.client # Raises StrictLoadingViolationError
  

  Previously, enabling strict loading would cause any lazily loaded association to raise an error. Using n_plus_one_only mode allows us to lazily load belongs_to, has_many, and other associations that are fetched through a single query.

  Dinah Shi

• Fix Float::INFINITY assignment to datetime column with postgresql adapter.

  Before:

  # With this config
  ActiveRecord::Base.time_zone_aware_attributes = true
  
  # and the following schema:
  create_table "postgresql_infinities" do |t|
    t.datetime "datetime"
  end
  
  # This test fails
  record = PostgresqlInfinity.create!(datetime: Float::INFINITY)
  assert_equal Float::INFINITY, record.datetime # record.datetime gets nil
  

  After this commit, record.datetime gets Float::INFINITY as expected.

  Shunichi Ikegami

• Type cast enum values by the original attribute type.

  The notable thing about this change is that unknown labels will no longer match 0 on MySQL.

  class Book < ActiveRecord::Base
    enum :status, { proposed: 0, written: 1, published: 2 }
  end
  

  Before:

  # SELECT `books`.* FROM `books` WHERE `books`.`status` = 'prohibited' LIMIT 1
  Book.find_by(status: :prohibited)
  # => #<Book id: 1, status: "proposed", ...> (for mysql2 adapter)
  # => ActiveRecord::StatementInvalid: PG::InvalidTextRepresentation: ERROR:  invalid input syntax for type integer: "prohibited" (for postgresql adapter)
  # => nil (for sqlite3 adapter)
  

  After:

  # SELECT `books`.* FROM `books` WHERE `books`.`status` IS NULL LIMIT 1
  Book.find_by(status: :prohibited)
  # => nil (for all adapters)
  

  Ryuta Kamizono

• Fixtures for has_many :through associations now load timestamps on join tables.

  Given this fixture:

  ### monkeys.yml
  george:
    name: George the Monkey
    fruits: apple
  
  ### fruits.yml
  apple:
    name: apple
  

  If the join table (fruit_monkeys) contains created_at or updated_at columns, these will now be populated when loading the fixture. Previously, fixture loading would crash if these columns were required, and leave them as null otherwise.

  Alex Ghiculescu

• Allow applications to configure the thread pool for async queries.

  Some applications may want one thread pool per database whereas others want to use a single global thread pool for all queries. By default, Rails will set async_query_executor to nil which will not initialize any executor. If load_async is called and no executor has been configured, the query will be executed in the foreground.

  To create one thread pool for all database connections to use applications can set config.active_record.async_query_executor to :global_thread_pool and optionally define config.active_record.global_executor_concurrency. This defaults to 4. For applications that want to have a thread pool for each database connection, config.active_record.async_query_executor can be set to :multi_thread_pool. The configuration for each thread pool is set in the database configuration.

  Eileen M. Uchitelle

• Allow new syntax for enum to avoid leading _ from reserved options.

  Before:

  class Book < ActiveRecord::Base
    enum status: [ :proposed, :written ], _prefix: true, _scopes: false
    enum cover: [ :hard, :soft ], _suffix: true, _default: :hard
  end
  

  After:

  class Book < ActiveRecord::Base
    enum :status, [ :proposed, :written ], prefix: true, scopes: false
    enum :cover, [ :hard, :soft ], suffix: true, default: :hard
  end
  

  Ryuta Kamizono

• Add ActiveRecord::Relation#load_async.

  This method schedules the query to be performed asynchronously from a thread pool.

  If the result is accessed before a background thread had the opportunity to perform the query, it will be performed in the foreground.

  This is useful for queries that can be performed long enough before their result will be needed, or for controllers which need to perform several independent queries.

  def index
    @categories = Category.some_complex_scope.load_async
    @posts = Post.some_complex_scope.load_async
  end
  

  Active Record logs will also include timing info for the duration of how long the main thread had to wait to access the result. This timing is useful to know whether or not it's worth to load the query asynchronously.

  DEBUG -- :   Category Load (62.1ms)  SELECT * FROM `categories` LIMIT 50
  DEBUG -- :   ASYNC Post Load (64ms) (db time 126.1ms)  SELECT * FROM `posts` LIMIT 100
  

  The duration in the first set of parens is how long the main thread was blocked waiting for the results, and the second set of parens with "db time" is how long the entire query took to execute.

  Jean Boussier

• Implemented ActiveRecord::Relation#excluding method.

  This method excludes the specified record (or collection of records) from the resulting relation:

  Post.excluding(post)
  Post.excluding(post_one, post_two)
  

  Also works on associations:

  post.comments.excluding(comment)
  post.comments.excluding(comment_one, comment_two)
  

  This is short-hand for Post.where.not(id: post.id) (for a single record) and Post.where.not(id: [post_one.id, post_two.id]) (for a collection).

  Glen Crawford

• Skip optimised #exist? query when #include? is called on a relation with a having clause.

  Relations that have aliased select values AND a having clause that references an aliased select value would generate an error when #include? was called, due to an optimisation that would generate call #exists? on the relation instead, which effectively alters the select values of the query (and thus removes the aliased select values), but leaves the having clause intact. Because the having clause is then referencing an aliased column that is no longer present in the simplified query, an ActiveRecord::InvalidStatement error was raised.

  A sample query affected by this problem:

  Author.select('COUNT(*) as total_posts', 'authors.*')
        .joins(:posts)
        .group(:id)
        .having('total_posts > 2')
        .include?(Author.first)
  

  This change adds an addition check to the condition that skips the simplified #exists? query, which simply checks for the presence of a having clause.

  Fixes #41417.

  Michael Smart

• Increment postgres prepared statement counter before making a prepared statement, so if the statement is aborted without Rails knowledge (e.g., if app gets killed during long-running query or due to Rack::Timeout), app won't end up in perpetual crash state for being inconsistent with PostgreSQL.

  wbharding, Martin Tepper

• Add ability to apply scoping to all_queries.

  Some applications may want to use the scoping method but previously it only worked on certain types of queries. This change allows the scoping method to apply to all queries for a model in a block.

  Post.where(blog_id: post.blog_id).scoping(all_queries: true) do
    post.update(title: "a post title") # adds `posts.blog_id = 1` to the query
  end
  

  Eileen M. Uchitelle

• ActiveRecord::Calculations.calculate called with :average (aliased as ActiveRecord::Calculations.average) will now use column-based type casting. This means that floating-point number columns will now be aggregated as Float and decimal columns will be aggregated as BigDecimal.

  Integers are handled as a special case returning BigDecimal always (this was the case before already).

  # With the following schema:
  create_table "measurements" do |t|
    t.float "temperature"
  end
  
  # Before:
  Measurement.average(:temperature).class
  # => BigDecimal
  
  # After:
  Measurement.average(:temperature).class
  # => Float
  

  Before this change, Rails just called to_d on average aggregates from the database adapter. This is not the case anymore. If you relied on that kind of magic, you now need to register your own ActiveRecord::Type (see ActiveRecord::Attributes::ClassMethods for documentation).

  Josua Schmid

• PostgreSQL: introduce ActiveRecord::ConnectionAdapters::PostgreSQLAdapter.datetime_type.

  This setting controls what native type Active Record should use when you call datetime in a migration or schema. It takes a symbol which must correspond to one of the configured NATIVE_DATABASE_TYPES. The default is :timestamp, meaning t.datetime in a migration will create a "timestamp without time zone" column. To use "timestamp with time zone", change this to :timestamptz in an initializer.

  You should run bin/rails db:migrate to rebuild your schema.rb if you change this.

  Alex Ghiculescu

• PostgreSQL: handle timestamp with time zone columns correctly in schema.rb.

  Previously they dumped as t.datetime :column_name, now they dump as t.timestamptz :column_name, and are created as timestamptz columns when the schema is loaded.

  Alex Ghiculescu

• Removing trailing whitespace when matching columns in ActiveRecord::Sanitization.disallow_raw_sql!.

  Gannon McGibbon, Adrian Hirt

• Expose a way for applications to set a primary_abstract_class.

  Multiple database applications that use a primary abstract class that is not named ApplicationRecord can now set a specific class to be the primary_abstract_class.

  class PrimaryApplicationRecord
    self.primary_abstract_class
  end
  

  When an application boots it automatically connects to the primary or first database in the database configuration file. In a multiple database application that then call connects_to needs to know that the default connection is the same as the ApplicationRecord connection. However, some applications have a differently named ApplicationRecord. This prevents Active Record from opening duplicate connections to the same database.

  Eileen M. Uchitelle, John Crepezzi

• Support hash config for structure_dump_flags and structure_load_flags flags. Now that Active Record supports multiple databases configuration, we need a way to pass specific flags for dump/load databases since the options are not the same for different adapters. We can use in the original way:

  ActiveRecord::Tasks::DatabaseTasks.structure_dump_flags = ['--no-defaults', '--skip-add-drop-table']
  # or
  ActiveRecord::Tasks::DatabaseTasks.structure_dump_flags = '--no-defaults --skip-add-drop-table'
  

  And also use it passing a hash, with one or more keys, where the key is the adapter

  ActiveRecord::Tasks::DatabaseTasks.structure_dump_flags = {
    mysql2: ['--no-defaults', '--skip-add-drop-table'],
    postgres: '--no-tablespaces'
  }
  

  Gustavo Gonzalez

• Connection specification now passes the "url" key as a configuration for the adapter if the "url" protocol is "jdbc", "http", or "https". Previously only urls with the "jdbc" prefix were passed to the Active Record Adapter, others are assumed to be adapter specification urls.

  Fixes #41137.

  Jonathan Bracy

• Allow to opt-out of strict_loading mode on a per-record base.

  This is useful when strict loading is enabled application wide or on a model level.

  class User < ApplicationRecord
    has_many :bookmarks
    has_many :articles, strict_loading: true
  end
  
  user = User.first
  user.articles                        # => ActiveRecord::StrictLoadingViolationError
  user.bookmarks                       # => #<ActiveRecord::Associations::CollectionProxy>
  
  user.strict_loading!(true)           # => true
  user.bookmarks                       # => ActiveRecord::StrictLoadingViolationError
  
  user.strict_loading!(false)          # => false
  user.bookmarks                       # => #<ActiveRecord::Associations::CollectionProxy>
  user.articles.strict_loading!(false) # => #<ActiveRecord::Associations::CollectionProxy>
  

  Ayrton De Craene

• Add FinderMethods#sole and #find_sole_by to find and assert the presence of exactly one record.

  Used when you need a single row, but also want to assert that there aren't multiple rows matching the condition; especially for when database constraints aren't enough or are impractical.

  Product.where(["price = %?", price]).sole
  # => ActiveRecord::RecordNotFound      (if no Product with given price)
  # => #<Product ...>                    (if one Product with given price)
  # => ActiveRecord::SoleRecordExceeded  (if more than one Product with given price)
  
  user.api_keys.find_sole_by(key: key)
  # as above
  

  Asherah Connor

• Makes ActiveRecord::AttributeMethods::Query respect the getter overrides defined in the model.

  Before:

  class User
    def admin
      false # Overriding the getter to always return false
    end
  end
  
  user = User.first
  user.update(admin: true)
  
  user.admin # false (as expected, due to the getter overwrite)
  user.admin? # true (not expected, returned the DB column value)
  

  After this commit, user.admin? above returns false, as expected.

  Fixes #40771.

  Felipe

• Allow delegated_type to be specified primary_key and foreign_key.

  Since delegated_type assumes that the foreign_key ends with _id, singular_id defined by it does not work when the foreign_key does not end with id. This change fixes it by taking into account primary_key and foreign_key in the options.

  Ryota Egusa

• Expose an invert_where method that will invert all scope conditions.

  class User
    scope :active, -> { where(accepted: true, locked: false) }
  end
  
  User.active
  # ... WHERE `accepted` = 1 AND `locked` = 0
  
  User.active.invert_where
  # ... WHERE NOT (`accepted` = 1 AND `locked` = 0)
  

  Kevin Deisz

• Restore possibility of passing false to :polymorphic option of belongs_to.

  Previously, passing false would trigger the option validation logic to throw an error saying :polymorphic would not be a valid option.

  glaszig

• Remove deprecated database kwarg from connected_to.

  Eileen M. Uchitelle, John Crepezzi

• Allow adding nonnamed expression indexes to be revertible.

  Previously, the following code would raise an error, when executed while rolling back, and the index name should be specified explicitly. Now, the index name is inferred automatically.

  add_index(:items, "to_tsvector('english', description)")
  

  Fixes #40732.

  fatkodima

• Only warn about negative enums if a positive form that would cause conflicts exists.

  Fixes #39065.

  Alex Ghiculescu

• Add option to run default_scope on all queries.

  Previously, a default_scope would only run on select or insert queries. In some cases, like non-Rails tenant sharding solutions, it may be desirable to run default_scope on all queries in order to ensure queries are including a foreign key for the shard (i.e. blog_id).

  Now applications can add an option to run on all queries including select, insert, delete, and update by adding an all_queries option to the default scope definition.

  class Article < ApplicationRecord
    default_scope -> { where(blog_id: Current.blog.id) }, all_queries: true
  end
  

  Eileen M. Uchitelle

• Add where.associated to check for the presence of an association.

  # Before:
  account.users.joins(:contact).where.not(contact_id: nil)
  
  # After:
  account.users.where.associated(:contact)
  

  Also mirrors where.missing.

  Kasper Timm Hansen

• Allow constructors (build_association and create_association) on has_one :through associations.

  Santiago Perez Perret

Please check 6-1-stable for previous changes.