Forward Compatibility¶ ↑

Sequel 4.49.0 will be the last minor release of Sequel 4. While the vast majority of backwards incompatible changes in Sequel 5 have deprecation warnings in 4.49.0, there are a few changes that do not. Here is a brief list of changes coming in Sequel 5 that do not have deprecation warnings (note that this list may not be exhaustive):

The {before,after,around}_validation hooks will always be called when saving, even if the validate: false option is used. This will allow you to use the before_validation hook to make changes to the model instance that are required before validation and before saving even if not validating. Currently, you would have to use both a before_save and before_validation hook, which would both be run on normal instance saving.
Getting values for newly created model instances after insertion now happens before after_create is called, instead of after. This behavior is currently available via the before_after_save plugin, and and will become the default behavior.
Sequel will now immediately attempt to the connect to the database when a Database instance is created, in order to fail fast. This behavior is currently available via the test: true option, and will become the default behavior. You can force not testing the connection by using the test: false option.
The validates_unique method in the validation_helpers plugin will now only check for uniqueness by default if the record is new or one of the related columns has been modified by default. You can use only_if_modified: false to force the uniqueness check.
Database schema methods and schema generator methods will return nil instead of some internal value.
Many cases where Sequel uses send internally will be switched to public_send so they only call public methods, unless it is specifically expected that they will call private methods.
Model association hooks will be nil instead of empty arrays by default. They will only be arrays if that hook has been set for the association.
Internal uses of instance_eval with a block will be changed to instance_exec. This will allow them to be used with lambdas that take no arguments. Unfortunately, it will break the case where a lambda is currently used that takes one argument.
Most internal constants will be frozen, unless there is a requirement that they be modified at runtime.
The @was_new instance variable set during model instance creation will be removed.

Deprecated Features¶ ↑

Model association before callbacks returning false canceling the action is now deprecated. The callbacks should now call Model#cancel_action to cancel the action.
Loading plugins by requiring them via sequel_#{plugin} is now deprecated. Affected plugins should move the plugin file so it can be required via sequel/plugins/#{plugin}.
In the mock adapter, Dataset#autoid=, _fetch=, and numrows= are now deprecated. They modified the dataset itself, which would not work for frozen datasets. Dataset#with_autoid, with_fetch, and with_numrows should be used instead, which return a modified copy.
In the null_dataset extension, Dataset#nullify! is now deprecated. It modified the dataset itself, which would not work for frozen datasets. Dataset#nullify should be used instead, which returns a modified copy.
Modifying the validation_helpers plugin DEFAULT_OPTIONS hash is now deprecated. Any change to the default options should be done by overriding the Model#default_validation_helpers_options private method.
Modifying ConnectionPool::CONNECTION_POOL_MAP to support an external connection pool is now deprecated. To use an external connection pool, pass the pool class via the :pool_class Database option. Additionally, using a :pool_class option that is not a class or a symbol for one of the default connection pools is also deprecated.
ConnectionPool#created_count is now deprecated. This method was misnamed, as it was in alias to size, but the name implies it returns how many connections have been created, as opposed to how many connections are still in the pool.
Sequel::SQL::Function#f is now deprecated, switch to using name instead.
Sequel::SQL::AliasedExpression#aliaz is now deprecated, switch to using alias instead.
The :eager_loading_predicate_key association option and eager_loading_predicate_key association method are now deprecated. The predicate_key option and method should be used instead.
The cti_columns class method in the class_table_inheritance plugin is now deprecated.
The serialized_columns class method in the serialization plugin is now deprecated.
Having ds.join_table(:table, :cross, :a=>:b) be treated as an inner join on MySQL is now deprecated.
Sequel::IBMDB::Connection#prepared_statements= in the ibmdb adapter is now deprecated.
Additional internal constants are now deprecated.

New Features¶ ↑

Database#extend_datasets and Database#with_extend if given a block now use a Dataset::DatasetModule instance instead of a plain Module instance. Dataset::DatasetModule is a subset of Model::DatasetModule, and allows for the easy creation of dataset methods that can perform caching for frozen datasets.

Defining dataset methods is done by calling methods with the same name as dataset methods inside the extend_datasets or with_extend block:
```
DB.extend_datasets do
  order :by_id, :id
  select :with_id_and_name, :id, :name
  where :active, :active
end
```
This is equivalent to:
```
DB.extend_datasets do
  def by_id
    order(:id)
  end

  def with_id_and_name
    select(:id, :name)
  end

  def active
    where(:active)
  end
end
```
Except that for frozen datasets (the default in Sequel 5), code like:
```
100.times do
  DB[:table].active.with_id_and_name.by_id
end
```
will only allocate 4 datasets instead of 400, and can be 3-4 times faster.
Dataset#where_{all,each,single_value} are now core dataset methods instead of just model dataset methods. These methods allow you to replace:
```
dataset.where(cond).all
dataset.where(cond).each{}
dataset.where(cond).single_value
```
with:
```
dataset.where_all(cond)
dataset.where_each(cond){}
dataset.where_single_value(cond)
```
The advantage of where_{all,each,single_value} is that frozen datasets can take potentially advantage of caching and perform 70%-300% faster.
Oracle 12 native limit/offset support is now supported, which in particular makes offset queries much faster as they don’t have to be emulated using the row_number window function.
Dataset#paged_each in the mysql2 adapter now supports a :stream=>false option to disable streaming and fallback to the default implementation.
The postgres adapter now supports the :sslrootcert option directly, you no longer need to specify it using the :driver_options hash.
The single_table_inheritance plugin now supports an sti_class_from_sti_key method for getting the appropriate subclass for the given key.

Other Improvements¶ ↑

Using the dataset_associations plugin with a many_through_many association that joins to the same table multiple times is now handled correctly by automatically aliasing the table appropriately.
On Ruby 2.1+, Sequel::Error#cause will use wrapped_exception if one is set. This doesn’t result in different behavior in most cases, but it can in cases where nested exception handling is done and Sequel tries to raise the most relevant exception.
Using the composition plugin with the :mapping option now works correctly when using the column_conflicts plugin.
The validation_helpers plugin’s validates_max_length method now correctly gets the default :nil_message option from the default_validation_helpers_options method instead of looking at the plugin defaults.
The duplicate_columns_handler extension no longer makes the Dataset#columns= method public.
On H2 1.4+, alter_table add_primary_key now works correctly.
The jdbc/sqlserver adapter’s datetimeoffset type handling now works with more JDBC driver versions.

4.49.0.txt

Forward Compatibility¶ ↑

Deprecated Features¶ ↑

New Features¶ ↑

Other Improvements¶ ↑