1 files changed, 162 insertions, 2 deletions
diff --git a/activerecord/CHANGELOG.md b/activerecord/CHANGELOG.md
index d1ae41ab97..96fd6a62c6 100644
--- a/activerecord/CHANGELOG.md
+++ b/activerecord/CHANGELOG.md
@@ -1,3 +1,163 @@
+*   Added `index` option for `change_table` migration helpers.
+    With this change you can create indexes while adding new
+    columns into the existing tables.
+
+    Example:
+
+        change_table(:languages) do |t|
+          t.string :country_code, index: true
+        end
+
+    *Mehmet Emin İNAÇ*
+
+*   Fix `transaction` reverting for migrations.
+
+    Before: Commands inside a `transaction` in a reverted migration ran uninverted.
+    Now: This change fixes that by reverting commands inside `transaction` block.
+
+    *fatkodima*, *David Verhasselt*
+
+*   Raise an error instead of scanning the filesystem root when `fixture_path` is blank.
+
+    *Gannon McGibbon*, *Max Albrecht*
+
+*   Allow `ActiveRecord::Base.configurations=` to be set with a symbolized hash.
+
+    *Gannon McGibbon*
+
+*   Don't update counter cache unless the record is actually saved.
+
+    Fixes #31493, #33113, #33117.
+
+    *Ryuta Kamizono*
+
+*   Deprecate `ActiveRecord::Result#to_hash` in favor of `ActiveRecord::Result#to_a`.
+
+    *Gannon McGibbon*, *Kevin Cheng*
+
+*   SQLite3 adapter supports expression indexes.
+
+    ```
+    create_table :users do |t|
+      t.string :email
+    end
+
+    add_index :users, 'lower(email)', name: 'index_users_on_email', unique: true
+    ```
+
+    *Gray Kemmey*
+
+*   Allow subclasses to redefine autosave callbacks for associated records.
+
+    Fixes #33305.
+
+    *Andrey Subbota*
+
+*   Bump minimum MySQL version to 5.5.8.
+
+    *Yasuo Honda*
+
+*   Use MySQL utf8mb4 character set by default.
+
+    `utf8mb4` character set with 4-Byte encoding supports supplementary characters including emoji.
+    The previous default 3-Byte encoding character set `utf8` is not enough to support them.
+
+    *Yasuo Honda*
+
+*   Fix duplicated record creation when using nested attributes with `create_with`.
+
+    *Darwin Wu*
+
+*   Configuration item `config.filter_parameters` could also filter out
+    sensitive values of database columns when call `#inspect`.
+    We also added `ActiveRecord::Base::filter_attributes`/`=` in order to
+    specify sensitive attributes to specific model.
+
+    ```
+    Rails.application.config.filter_parameters += [:credit_card_number]
+    Account.last.inspect # => #<Account id: 123, name: "DHH", credit_card_number: [FILTERED] ...>
+    SecureAccount.filter_attributes += [:name]
+    SecureAccount.last.inspect # => #<SecureAccount id: 42, name: [FILTERED], credit_card_number: [FILTERED] ...>
+    ```
+
+    *Zhang Kang*
+
+*   Deprecate `column_name_length`, `table_name_length`, `columns_per_table`,
+    `indexes_per_table`, `columns_per_multicolumn_index`, `sql_query_length`,
+    and `joins_per_query` methods in `DatabaseLimits`.
+
+    *Ryuta Kamizono*
+
+*   `ActiveRecord::Base.configurations` now returns an object.
+
+    `ActiveRecord::Base.configurations` used to return a hash, but this
+    is an inflexible data model. In order to improve multiple-database
+    handling in Rails, we've changed this to return an object. Some methods
+    are provided to make the object behave hash-like in order to ease the
+    transition process. Since most applications don't manipulate the hash
+    we've decided to add backwards-compatible functionality that will throw
+    a deprecation warning if used, however calling `ActiveRecord::Base.configurations`
+    will use the new version internally and externally.
+
+    For example, the following `database.yml`:
+
+    ```
+    development:
+      adapter: sqlite3
+      database: db/development.sqlite3
+    ```
+
+    Used to become a hash:
+
+    ```
+    { "development" => { "adapter" => "sqlite3", "database" => "db/development.sqlite3" } }
+    ```
+
+    Is now converted into the following object:
+
+    ```
+    #<ActiveRecord::DatabaseConfigurations:0x00007fd1acbdf800 @configurations=[
+      #<ActiveRecord::DatabaseConfigurations::HashConfig:0x00007fd1acbded10 @env_name="development",
+        @spec_name="primary", @config={"adapter"=>"sqlite3", "database"=>"db/development.sqlite3"}>
+      ]
+    ```
+
+    Iterating over the database configurations has also changed. Instead of
+    calling hash methods on the `configurations` hash directly, a new method `configs_for` has
+    been provided that allows you to select the correct configuration. `env_name`, and
+    `spec_name` arguments are optional. For example these return an array of
+    database config objects for the requested environment and a single database config object
+    will be returned for the requested environment and specification name respectively.
+
+    ```
+    ActiveRecord::Base.configurations.configs_for(env_name: "development")
+    ActiveRecord::Base.configurations.configs_for(env_name: "development", spec_name: "primary")
+    ```
+
+    *Eileen M. Uchitelle*, *Aaron Patterson*
+
+*   Add database configuration to disable advisory locks.
+
+    ```
+    production:
+      adapter: postgresql
+      advisory_locks: false
+    ```
+
+    *Guo Xiang*
+
+*   SQLite3 adapter `alter_table` method restores foreign keys.
+
+    *Yasuo Honda*
+
+*   Allow `:to_table` option to `invert_remove_foreign_key`.
+
+    Example:
+
+       remove_foreign_key :accounts, to_table: :owners
+
+    *Nikolay Epifanov*, *Rich Chen*
+
 *   Add environment & load_config dependency to `bin/rake db:seed` to enable
     seed load in environments without Rails and custom DB configuration
 
@@ -64,8 +224,8 @@
 
     *Eddie Lebow*
 
-*   Add ActiveRecord::Base.create_or_find_by/! to deal with the SELECT/INSERT race condition in
-    ActiveRecord::Base.find_or_create_by/! by leaning on unique constraints in the database.
+*   Add `ActiveRecord::Base.create_or_find_by`/`!` to deal with the SELECT/INSERT race condition in
+    `ActiveRecord::Base.find_or_create_by`/`!` by leaning on unique constraints in the database.
 
     *DHH*