New Features¶ ↑

An :extensions Database option is now supported, which will load the named extensions into the Database before any connections are initiated:

DB = Sequel.connect('mock:///', :extensions=>[:error_sql, :synchronize_sql])
DB = Sequel.connect('mock:///?extensions=error_sql,synchronize_sql')

A :connect_sqls Database option is now supported, which will issue the given queries on all new connections:

DB = Sequel.connect('postgres:///', :connect_sqls=>[
    'SET random_page_cost = 1.0',
    "SET default_tablespace = 'foo'"
  ])

DatasetModule#reverse has been added for simpler use of descending orders:

class Foo < Sequel::Model
  dataset_module do
    reverse :newest_first, :created_at
  end
end
Foo.newest_first.first(10)

A synchronize_sql extension has been added. This extension checks out a connection around SQL string creation, and is useful in the cases where escaping values in the query requires a connection and a large number of values need to be escaped.
The following features are now supported on MariaDB 10.2+:
- Common table expressions.
- Window functions.
- Dropping CHECK constraints. Older versions of MariaDB/MySQL ignored CHECK constraints that were added, and Sequel did not attempt to filter them out, so Sequel did not require changes to add CHECK constraints. MariaDB 10.2 CHECK constraints work correctly with Sequel’s constraint_validations extension/plugin.
- Raising CHECK constraint violations as Sequel::CheckConstraintViolation instances.
- Recognizing curdate() as Sequel::CURRENT_DATE when used as the default value for a date column.
Date::Infinity values are now supported in the pg_extended_date_support extension:
```
DB.convert_infinite_timestamps = :date
```
This returns infinite dates/timestamps as Date::Infinity instances, and literalizes Date::Infinity instances correctly.

Improvements¶ ↑

Database#reset_primary_key_sequence now works correctly on PostgreSQL 10.
If a commit or rollback raises an exception when using the postgres adapter, Sequel will check the connection’s current transaction status and only send another rollback if the connection is currently inside a transaction. This fixes a warning that is issued in most cases if a commit or rollback fails.
The jdbc/postgresql adapter now forces JDBC PreparedStatement instances created by Dataset#call to never be prepared server side, working around an caching issue in the jdbc-postgres drier in versions greater than 9.4.1200.
Database#indexes will no longer return indexes which are in the process of being dropped on PostgreSQL 9.3+. Additionally, Database#indexes will now return indexes that have indcheckxmin set. The previous removal of indexes with indcheckxmin set is more likely to cause false negatives than correctly remove indexes not yet valid.
Common table expressions are no longer hoisted from subqueries on SQLite. They are still hoisted from queries used in UNION/INSERT/EXCEPT, since SQLite does not support common table expressions at that level.
On Microsoft SQL Server, using an INSERT query with a subquery that uses a common table expression now hoists the common table expression from subquery level to main query level, allowing such queries to work.
An additional disconnect error is now recognized in the oracle adapter.
bin/sequel now adds a Database logger before the initial connection is made, allowing you to see any connection setup statements issued to the database.

Backwards Compatibility¶ ↑

Calling a filtering method with no argument and a virtual row block that returns nil on a dataset with no existing filter is deprecated in this version and will emit a warning. The behavior in this version remains the same, where the dataset is not modified. The behavior will change in Sequel 5.4.0 so that a WHERE NULL filter will be added in that case, instead of the filter being ignored, so that the behavior is similar to calling the filtering method with a nil argument.
```
# Sequel 5.3.0
DB[:a].where{nil}
# SELECT * FROM a

# Sequel 5.4.0
DB[:a].where{nil}
# SELECT * FROM a WHERE NULL
```
Support for PostgreSQL <8.1 has been dropped from Database#indexes. Sequel’s PostgreSQL support requires >=8.2 for Dataset#insert to work, so it doesn’t make sense to support earlier versions in other cases.