docs: add about DB transactions in changelog

Author: kenjis

user_guide_src/source/changelogs/v4.3.0.rst

@@ -27,16 +27,22 @@ Exceptions when Database Errors Occur
 
 - The exceptions thrown by the database connection classes have been changed to ``CodeIgniter\Database\Exceptions\DatabaseException``. Previously, different database drivers threw different exception classes, but these have been unified into ``DatabaseException``.
 - The exceptions thrown by the ``execute()`` method of Prepared Queries have been changed to ``DatabaseException``. Previously, different database drivers might throw different exception classes or did not throw exceptions, but these have been unified into ``DatabaseException``.
-- ``DBDebug`` and ``CI_DEBUG``
+- ``DBDebug`` and ``CI_DEBUG`` Changes
 
     - To be consistent in behavior regardless of environments, ``Config\Database::$default['DBDebug']``
       and ``Config\Database::$tests['DBDebug']`` has been changed to ``true`` by default. With these
-      settings, an exception is always thrown when a database error occurs.
+      settings, an exception is always thrown when a database error occurs. Previously, it is ``false``
+      **only in the production environment**.
     - Now ``DatabaseException`` thrown in ``BaseBuilder`` is thrown if ``$DBDebug`` is true.
       Previously, it is thrown if ``CI_DEBUG`` is true.
     - The default value of ``BaseConnection::$DBDebug`` has been changed to ``true``.
     - With these changes, ``DBDebug`` **now means whether or not to throw an exception when an error occurs**.
       Although unrelated to debugging, the name has not been changed.
+    - When running transactions with ``DBDebug`` is ``true``, if a query error occurs, all the queries
+      will be rolled backed, and an exception will be thrown. :ref:`transactions-managing-errors` or
+      :ref:`transactions-manual-transactions` won't work. This is no different from previous versions,
+      but changing the ``DBDebug`` setting from the previous default value to ``true`` will change the
+      behavior in the production environment.
     - Now when you delete without WHERE clause in ``Model``, ``DatabaseException`` is thrown even if
       ``CI_DEBUG`` is false. Previously, it is thrown if ``CI_DEBUG`` is true.
 

user_guide_src/source/database/transactions.rst

@@ -72,6 +72,8 @@ Strict Mode can be disabled as follows:
     and different database drivers might throw different exception classes
     or did not throw exceptions.
 
+.. _transactions-managing-errors:
+
 Managing Errors
 ===============
 
@@ -111,6 +113,8 @@ a valid result. To use test mode simply set the first parameter in the
 
 .. literalinclude:: transactions/005.php
 
+.. _transactions-manual-transactions:
+
 Running Transactions Manually
 =============================