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diff --git a/activerecord/CHANGELOG.md b/activerecord/CHANGELOG.md
index 8875b7ae25..e1cace7d88 100644
--- a/activerecord/CHANGELOG.md
+++ b/activerecord/CHANGELOG.md
@@ -1,3 +1,232 @@
+*   Use SQL COUNT and LIMIT 1 queries for `none?` and `one?` methods if no block or limit is given,
+    instead of loading the entire collection to memory.
+    This applies to relations (e.g. `User.all`) as well as associations (e.g. `account.users`)
+
+        # Before:
+
+        users.none?
+        # SELECT "users".* FROM "users"
+
+        users.one?
+        # SELECT "users".* FROM "users"
+
+        # After:
+
+        users.none?
+        # SELECT 1 AS one FROM "users" LIMIT 1
+
+        users.one?
+        # SELECT COUNT(*) FROM "users"
+
+    *Eugene Gilburg*
+
+*   Allow `:precision` option for time type columns.
+
+    *Ryuta Kamizono*
+
+*   Have `enum` perform type casting consistently with the rest of Active
+    Record, such as `where`.
+
+    *Sean Griffin*
+
+*   `scoping` no longer pollutes the current scope of sibling classes when using
+    STI. e.x.
+
+    StiOne.none.scoping do
+      StiTwo.all
+    end
+
+    Fixes #18806.
+
+    *Sean Griffin*
+
+*   `remove_reference` with `foreign_key: true` removes the foreign key before
+    removing the column. This fixes a bug where it was not possible to remove
+    the column on MySQL.
+
+    Fixes #18664.
+
+    *Yves Senn*
+
+*   `find_in_batches` now accepts an `:end_at` parameter that complements the `:start`
+     parameter to specify where to stop batch processing.
+
+    *Vipul A M*
+
+*   Fix rounding problem for PostgreSQL timestamp column.
+
+    If timestamp column have the precision, it need to format according to
+    the precision of timestamp column.
+
+    *Ryuta Kamizono*
+
+*   Respect the database default charset for `schema_migrations` table.
+
+    The charset of `version` column in `schema_migrations` table is depend
+    on the database default charset and collation rather than the encoding
+    of the connection.
+
+    *Ryuta Kamizono*
+
+*   Raise `ArgumentError` when passing `nil` or `false` to `Relation#merge`.
+
+    These are not valid values to merge in a relation so it should warn the users
+    early.
+
+    *Rafael Mendonça França*
+
+*   Use `SCHEMA` instead of `DB_STRUCTURE` for specifying structure file.
+
+    This makes the db:structure tasks consistent with test:load_structure.
+
+    *Dieter Komendera*
+
+*   Respect custom primary keys for associations when calling `Relation#where`
+
+    Fixes #18813.
+
+    *Sean Griffin*
+
+*   Fixed several edge cases which could result in a counter cache updating
+    twice or not updating at all for `has_many` and `has_many :through`.
+
+    Fixes #10865.
+
+    *Sean Griffin*
+
+*   Foreign keys added by migrations were given random, generated names. This
+    meant a different `structure.sql` would be generated every time a developer
+    ran migrations on their machine.
+
+    The generated part of foreign key names is now a hash of the table name and
+    column name, which is consistent every time you run the migration.
+
+    *Chris Sinjakli*
+
+*   Validation errors would be raised for parent records when an association
+    was saved when the parent had `validate: false`. It should not be the
+    responsibility of the model to validate an associated object unless the
+    object was created or modified by the parent.
+
+    This fixes the issue by skipping validations if the parent record is
+    persisted, not changed, and not marked for destruction.
+
+    Fixes #17621.
+
+    *Eileen M. Uchitelle, Aaron Patterson*
+
+*   Fix n+1 query problem when eager loading nil associations (fixes #18312)
+
+    *Sammy Larbi*
+
+*   Change the default error message from `can't be blank` to `must exist` for
+    the presence validator of the `:required` option on `belongs_to`/`has_one` associations.
+
+    *Henrik Nygren*
+
+*   Fixed ActiveRecord::Relation#group method when argument is SQL reserved key word:
+
+    Example:
+
+        SplitTest.group(:key).count
+        Property.group(:value).count
+
+    *Bogdan Gusiev*
+
+*   Added the `#or` method on ActiveRecord::Relation, allowing use of the OR
+    operator to combine WHERE or HAVING clauses.
+
+    Example:
+
+        Post.where('id = 1').or(Post.where('id = 2'))
+        # => SELECT * FROM posts WHERE (id = 1) OR (id = 2)
+
+    *Sean Griffin*, *Matthew Draper*, *Gael Muller*, *Olivier El Mekki*
+
+*   Don't define autosave association callbacks twice from
+    `accepts_nested_attributes_for`.
+
+    Fixes #18704.
+
+    *Sean Griffin*
+
+*   Integer types will no longer raise a `RangeError` when assigning an
+    attribute, but will instead raise when going to the database.
+
+    Fixes several vague issues which were never reported directly. See the
+    commit message from the commit which added this line for some examples.
+
+    *Sean Griffin*
+
+*   Values which would error while being sent to the database (such as an
+    ASCII-8BIT string with invalid UTF-8 bytes on SQLite3), no longer error on
+    assignment. They will still error when sent to the database, but you are
+    given the ability to re-assign it to a valid value.
+
+    Fixes #18580.
+
+    *Sean Griffin*
+
+*   Don't remove join dependencies in `Relation#exists?`
+
+    Fixes #18632.
+
+    *Sean Griffin*
+
+*   Invalid values assigned to a JSON column are assumed to be `nil`.
+
+    Fixes #18629.
+
+    *Sean Griffin*
+
+*   Add `ActiveRecord::Base#accessed_fields`, which can be used to quickly
+    discover which fields were read from a model when you are looking to only
+    select the data you need from the database.
+
+    *Sean Griffin*
+
+*   Introduce the `:if_exists` option for `drop_table`.
+
+    Example:
+
+        drop_table(:posts, if_exists: true)
+
+    That would execute:
+
+        DROP TABLE IF EXISTS posts
+
+    If the table doesn't exist, `if_exists: false` (the default) raises an
+    exception whereas `if_exists: true` does nothing.
+
+    *Cody Cutrer*, *Stefan Kanev*, *Ryuta Kamizono*
+
+*   Don't run SQL if attribute value is not changed for update_attribute method.
+
+    *Prathamesh Sonpatki*
+
+*   `time` columns can now get affected by `time_zone_aware_attributes`. If you have
+    set `config.time_zone` to a value other than `'UTC'`, they will be treated
+    as in that time zone by default in Rails 5.1. If this is not the desired
+    behavior, you can set
+
+        ActiveRecord::Base.time_zone_aware_types = [:datetime]
+
+    A deprecation warning will be emitted if you have a `:time` column, and have
+    not explicitly opted out.
+
+    Fixes #3145.
+
+    *Sean Griffin*
+
+*   Tests now run after_commit callbacks. You no longer have to declare
+    `uses_transaction ‘test name’` to test the results of an after_commit.
+
+    after_commit callbacks run after committing a transaction whose parent
+    is not `joinable?`: un-nested transactions, transactions within test cases,
+    and transactions in `console --sandbox`.
+
+    *arthurnn*, *Ravil Bayramgalin*, *Matthew Draper*
+
 *   `nil` as a value for a binary column in a query no longer logs as
     "<NULL binary data>", and instead logs as just "nil".