Database#copy_into in the jdbc/postgresql adapter now works correctly when using multibyte characters in strings.
The alter_table add_foreign_key method is now reversible when the :foreign_key_constraint_name option is used.
The jdbc/h2 and jdbc/hsqldb adapters now respect the :foreign_key_constraint_name option.
Calling Model.freeze on an already frozen model no longer raises an error.
An unnecessary database query is now avoided when loading the pg_inet extension when the pg_array extension is already loaded.
A better exception message is now used when migrating with an empty migration directory.
Model.allowed_columns has been removed. Use the whitelist_security plugin if you want to call it.
Model use_after_commit_rollback class and instance accessors have been removed.
Support for the Model#_before_validation method has been removed.
The private Model.plugin_module_defined? method has been removed.