New Features¶ ↑

A before_after_save plugin has been added, which for newly created objects refreshes the object before calling after_create, and resets the modified flag before calling after_update. Previously, these actions were not taken until after after_save was called. This will be the default behavior in Sequel 5.
In create_table blocks, primary_key now supports a :keep_order option, which will not change the order in which the primary key is added. Without this option, Sequel’s historical behavior of making the primary key column the first column is used.
```
DB.create_table(:foo) do
  Integer :a
  primary_key :b, :keep_order=>true
end
# CREATE TABLE foo
# (a integer, b integer PRIMARY KEY AUTOINCREMENT)
```
The schema dumper now uses this option if necessary, allowing it to correctly dump tables where the primary key column is not the first column.
Dataset#single_record! and single_value! have been added. These are faster versions of single_record and single_value that don’t require cloning the dataset. If you are sure the dataset will only return a single row or a single value, you can use these methods for better performance.

The new jsonb and json functions added in PostgreSQL 9.5 are now supported by the pg_json_ops extension.

Sequel.pg_jsonb_op(:metadata).set(%w'a b', [1,2,3])
# jsonb_set("metadata", ARRAY['a','b'], '[1,2,3]'::jsonb, true)

Other Improvements¶ ↑

Sequel.synchronize is no longer a stub on MRI. Testing has shown that relying on the global interpreter lock to protect multi-threaded access to hashes is not safe in all environments, so Sequel now uses a mutex on MRI just as it does on other ruby interpreters.
Database#schema now sets the :auto_increment option correctly for auto incrementing primary keys if they are not the first column in the table.
Dataset#single_value and with_sql_single_value are now slightly faster by avoiding an array allocation.
Model datasets can now use with_sql_single_value and return a single value, instead of an array in [:column_name, value] format.
Model#persisted? in the active_model plugin will now return false if the transaction that inserts the row for the object is rolled back.
bin/sequel now warns if additional arguments are passed that it ignores. In Sequel 5, bin/sequel will raise an error in these cases.
Database#foreign_key_list on PostgreSQL now returns referenced composite keys in the correct order.
The postgres adapter now works with postgres-pr 0.7.0. Note that postgres adapter users that want a pure-ruby driver are encouraged to use jeremyevans-postgres-pr as that has many additional bugfixes and is the version tested with Sequel on a regular basis.
The jdbc/postgresql adapter now recognizes an additional disconnect error.

Users who were relying on with_sql_single_value returning an array instead of a single value for model datasets need to update their code.