ANN: Sequel 3.31.0 Released

Sequel is a lightweight database access toolkit for Ruby.

  • Sequel provides thread safety, connection pooling and a concise
    DSL for constructing SQL queries and table schemas.
  • Sequel includes a comprehensive ORM layer for mapping records to
    Ruby objects and handling associated records.
  • Sequel supports advanced database features such as prepared
    statements, bound variables, stored procedures, savepoints,
    two-phase commit, transaction isolation, master/slave
    configurations, and database sharding.
  • Sequel currently has adapters for ADO, Amalgalite, DataObjects,
    DB2, DBI, Firebird, IBM_DB, Informix, JDBC, MySQL, Mysql2, ODBC,
    OpenBase, Oracle, PostgreSQL, SQLite3, Swift, and TinyTDS.

Sequel 3.31.0 has been released and should be available on the gem

= New Features

  • The serialization plugin can now support custom serialization
    formats, by supplying a serializer/deserializer pair of
    callable objects. You can also register custom deserializers
    via Sequel::Plugins::Serialization.register_format, so that
    they can be referenced by name. Example:

    lambda{|v| v.reverse},
    lambda{|v| v.reverse})
    class User < Sequel::Model
    serialize_attributes :reverse, :password

  • Dataset#import and #multi_insert now support a
    :return=>:primary_key option. When this option is used, the
    methods return an array of primary key values, one for each
    inserted row. Usage of this option on MySQL requires that a
    separate query be issued per row (instead of the single
    query for all rows that MySQL would usually use).

  • PostgreSQL can now use Dataset#returning in conjunction with
    import/multi_insert to set a custom column to return.

  • Microsoft SQL Server can now use Dataset#output in conjection with
    import/multi_insert to set a custom column to return.

  • Dataset#import and #multi_insert now respect a :server option to
    set the server/shard on which to execute the queries.
    Additionally, options given to this method are also passed to

  • Dataset#insert_multiple now returns an array of inserted primary

  • Model.def_column_alias has been added to make it easy to create
    alias methods for columns. This is useful if you have a legacy
    database and want to create friendly method names for the
    underlying columns. Note that this alias only affects the setter
    and getter methods. This does not affect the dataset level, so you
    still need to use the actual column names in dataset filters.

  • many_to_one associations can now have the same name as the related
    foreign key column, using the :key_column option. Use of this
    feature is not recommended, as it is much better to either rename
    the column or rename the association. Here’s an example of usage:

    Example schema:

    albums artists

    :id /–> :id

    :artist --/ :name


    class Album < Sequel::Model
    def_column_alias(:artist_id, :artist)
    many_to_one :artist, :key_column=>:artist

  • The mock adapter can now mock out database types, by providing a
    shared adapter name as the host (e.g. mock://postgres). This
    emulation is not perfect, but in most cases it allows you to see
    what SQL Sequel would generate on a given database without needing
    to install the required database driver.

  • Sequel now supports creating full text indexes on Microsoft SQL
    Server. Before using it, you must have previously setup a default
    full text search catalog, and you need to provide a :key_index
    option with an index name symbol.

  • Dataset#group_rollup and #group_cube methods have been added for
    GROUP BY ROLLUP and GROUP BY CUBE support. These features are in
    a recent SQL standard, and they are supported to various degrees on
    Microsoft SQL Server, DB2, Oracle, MySQL, and Derby.

  • Dataset#full_text_search on Microsoft SQL Server now supports
    multiple search terms.

  • The jdbc adapter now supports a :login_timeout option, giving the
    timeout in seconds.

= Other Improvements

  • Dataset#exists can now be used with prepared statement

  • Dataset#full_text_search can now be used with prepared statement
    placeholders on PostgreSQL, MySQL, and Microsoft SQL Server.

  • If tables from two separate schema are detected when parsing the
    schema for a table on PostgreSQL, an error is now raised.
    Previously, no error was raised, which led to weird errors later,
    such as duplicate columns in a model’s primary_key.

  • RETURNING is now supported with UPDATE/DELETE on PostgreSQL 8.2+.
    Previously, Sequel only supported it on 9.1+, but PostgreSQL
    introduced support for it in 8.2.

  • The shared postgres adapter now correctly handles the return value
    for Dataset#insert if you provide a separate column array and value
    array on PostgreSQL < 8.2.

  • Handle case in the PostgreSQL adapter where the server version
    cannot be determined via a query.

  • H2 clob types are now treated as string instead of as blob.
    Treating clob as blob breaks on H2, as it doesn’t automatically
    hex-unescape the input for clobs as it does for blobs.

  • Dataset#empty? now works correctly when the dataset has an offset
    and offset support is being emulated.

  • The mock adapter no longer defaults to downcasing identifiers on

= Backwards Compatibility

  • Dataset#exists now returns a PlaceholderLiteralString instead of a
    LiteralString, which could potentially break some code. If you
    would like a String returned, you can pass the returned object to


  • Dataset#from no longer handles :a__b__c___d as “a.b.c AS d”. This
    was not the intended behavior, and nowhere else in Sequel is a
    symbol treated that way. Now, Dataset#from is consistent with the
    rest of Sequel, using “a.b__c AS d”. This should only affect
    people in very rare cases, as most databases don’t use three level
    qualified tables. One exception is Microsoft SQL Server, which can
    use three level qualified tables for cross-database access.

  • Previously, Dataset#insert_multiple returned an array of hashes, now
    it returns an array of primary key values.

  • Dataset#EXRACT_CLOSE in the shared sqlite adapter has been renamed to

  • Dataset::StoredProcedureMethods::SQL_QUERY_TYPE and
    Dataset::ArgumentMapper::SQL_QUERY_TYPE constants have been removed,
    as have related sql_query_type private methods.

  • The serialization plugin was significantly refactored.
    Model.serialization_map now contains a callable object instead of a
    Symbol, and Model.serialization_format has been removed.
    Model.define_serialized_attribute_accessors private method now takes
    two callable objects before the columns, instead of a single symbol.