ANN: Sequel 3.37.0 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 3.37.0 has been released and should be available on the gem

= New Features

  • Database#extension and Dataset#extension have been added and
    make it much easier to use extensions that just define modules,
    where you previously had to manually extend a Database or
    Dataset object with the module to get the extension’s behavior.
    These methods operate similarly to model plugins, where you just
    specify the extension symbol, except that you can specify multiple
    extensions at once:

    DB.extension(:pg_array, :pg_hstore)

    For databases, these modify the Database itself (and
    potentially all of its datasets). Dataset#extension operates
    like other dataset methods, returning a modified clone of
    the dataset with the extension added:

    dataset = dataset.extension(:columns_introspection)

    Dataset#extension! has also been added for modifying the
    receiver instead of returning a clone.

    Not all extensions are usable by Database#extension or
    Dataset#extension, the extension has to have specific support
    for it. The following extensions support both
    Database#extension and Dataset#extension:

    • columns_introspection
    • query_literals
    • split_array_nil

    The following extensions support just Database#extension:

    • arbitrary_servers
    • looser_typecasting
    • pg_array
    • pg_auto_parameterize
    • pg_hstore
    • pg_inet
    • pg_interval
    • pg_json
    • pg_range
    • pg_statement_cache
    • server_block

    Any user that was loading these extensions with Sequel.extension
    and then manually extending objects with the extension’s module
    is encouraged to switch to Database#extension and/or

  • Dataset join methods now respect a :qualify=>:deep option
    to do deep qualification of expressions, allowing qualification
    of subexpressions in the expression tree. This can allow you
    to do things like:

    DB[:a].join(:b, {:c.cast(Integer)=>:d.cast(Integer)},



    For backwards compatibility, by default Sequel will only do
    automatic qualification if the arguments are simple symbols.
    This may change in a future version, if automatic qualification
    of only symbols is desired, switch to using :qualify=>:symbol.

    You can also choose to do no automatic qualification using the
    :qualify=>false option.

  • All of Sequel’s model associations now work with key expressions
    that are not simple column references, without creating a fully
    custom association. So you can create associations where the
    primary/foreign key values are stored in PostgreSQL array or
    hstore columns, for example.

  • The pg_array extension has now been made more generic, so that it
    is easy to support array types for any scalar type that is
    currently supported. All scalar types that Sequel’s postgres
    adapter supports now have corresponding array types supported in
    the pg_array extension. So if you load the pg_array extension and
    return a date array column, the returned values will be arrays of
    ruby Date objects.

    Other pg_* extensions that add support for PostgreSQL-specific
    scalar types now support array versions of those types if the
    pg_array extension is loaded first.

  • A pg_range extension has been added, making it easy to deal
    with PostgreSQL 9.2+'s range types. As ruby’s Range class does
    not support all PostgreSQL range type values (such as empty ranges,
    unbounded ranges, or ranges with an exlusive beginning), range
    types are returned as instances of Sequel::Postgres::PGRange, which
    has an API similar to Range. You can turn a PGRange into a Range
    using PGRange#to_range, assuming that the range type value does not
    use features that are incompatible with ruby’s Range class.

    The pg_range extension supports all range types supported by
    default in PostgreSQL 9.2, and makes it easy to support custom
    range types.

  • A pg_range_ops extension has been added, which adds DSL support for
    PostgreSQL range operators and functions, similar to the
    pg_array_ops and pg_hstore_ops extensions.

  • A pg_interval extension has been added, which makes Sequel return
    PostgreSQL interval types as instances of ActiveSupport::Duration.
    This is useful if you want to take the interval value and use it in
    calculations in ruby (assuming you load the appropriate parts of

  • A split_array_nil extension has been added, which changes how Sequel
    compiles IN/NOT IN expressions with arrays with nil values.

    where(:col=>[1, nil])


    WHERE (col IN (1, NULL))

    with split_array_nil extension:

    WHERE ((col IN (1)) OR (col IS NULL))

    exclude(:col=>[1, nil])


    WHERE (col NOT IN (1, NULL))

    with split_array_nil extension:

    WHERE ((col NOT IN (1)) AND (col IS NOT NULL))

  • The nested_attributes plugin now allows the :fields option to
    be a proc, which is called with the associated object and should
    return an array of allowable fields.

  • You can now specify the graph alias base when using eager_graph on
    a per-call basis. Previously, it could only be set on a per
    association basis. This is helpful if you have multiple
    associations to the same class, and are cascading the eager graph to
    dependent associations of that class for both of the associations.
    Previously, there was no way to manually give descriptive names to
    the tables in the cascaded associations, but you can now do so
    by passing the association as an Sequel::SQL::AliasedExpression
    instance instead of a plain Symbol. Here’s a usage example:

    ds = Game.eager_graph(:winner=>,

  • many_through_many associations now differentiate between column
    references and method references, by supporting the
    :left_primary_key_column and :right_primary_key_method options that
    many_to_many associations support.

  • Custom :eager_loader procs that accept a single hash argument now
    have an additional entry passed in the hash, :id_map, which is
    easier to use than the :key_hash entry (which is still present for
    backwards compatibility). Anyone with custom :eager_loader procs is
    encouraged to switch from using :key_hash to :id_map.

  • You can now override the create_table/alter_table schema generators
    per database/adapter. This allows for database specific generator
    subclasses, which have methods for unique features for that

  • You can now setup exclusion constraints on PostgreSQL using the
    create_table and alter_table schema generators:

    DB.create_table(:t) do

    exclusion_constraint([[:col1, ‘&&’], [:col2, ‘=’]])
    # EXCLUDE USING gist (col1 WITH &&, col2 WITH =)

    One common use for exclusion constraints is to make sure that no two
    rows have overlapping values/ranges/circles.

  • When adding foreign key constraints to an existing table on
    PostgreSQL, you can use the :not_valid option to mark the constraint
    as not yet valid. This will make it so that future changes to the
    table need to respect the foreign key constraint, but existing rows
    do not. After cleaning up the existing data, you can then use the
    alter_table validate_constraint method to mark the constraint as

  • An eval_inspect extension has been added that attempts to do
    do the following for Sequel::SQL::Expression instances:

    eval(obj.inspect) == obj # => true

    There are a lot of cases that this extension does not handle, but
    it does a decent job in most cases. This is currently only used
    internally in a specific case in the schema_dumper extension.

= Other Improvements

  • The filter by associations support now respects the method
    reference vs column reference distinction that other parts of the
    association code have respected since 3.32.0.

  • In the nested_attributes plugin, new one_to_one associated
    values are saved once instead of twice. Previously it attempted to
    save them before they were associated to the current model object,
    which can violate some validations/constraints.

  • When saving an associated object in the one_to_one association
    setter method, Sequel no longer adds an unnecessary filter
    condition when nullifying the foreign key for existing rows
    in the associated table.

  • The list plugin’s before_create method now calls super, which
    fixes usage when other plugins that define before_create are loaded
    before it.

  • In the pg_array extension, when typecasting an Array to PGArray,
    a recursive map is done on the input array to convert each value
    in the input array to the expected type, using the typecasting
    method that would be used for the scalar value. For example, for
    model objects, where ids is an integer array column:

    model.set(:ids=>[‘1’, ‘2’]).ids.to_a # => [1, 2]

  • The pg_array extension now correctly handles bytea arrays used
    in bound variables.

  • The pg_array extension no longer uses the JSON-based parser for
    floating point types, since it doesn’t handle NaN and Infinity
    values correctly.

  • When typecasting in the pg_array extension, PGArray values are
    only returned verbatim if they have a matching database type.
    Otherwise, the underlying array is rewrapped in a new PGArray
    value with the correct database type.

  • H2 clob types are now recognized as strings instead of blobs.
    Previously the code attempted to do this, but it didn’t do so

  • The jdbc/postgres adapter now converts scalar values of
    the array to the appropriate type. Previously, if you retrieved
    a date array, you got back a ruby array of JavaSQL::SQL::Date
    instances. Now, you get back a ruby array of ruby Date instances.

  • The schema_dumper extension now dumps migrations as change
    migrations, instead of separate up/down migrations, resulting in
    simpler code.

  • When dumping non-integer foreign keys in the schema dumper, an
    explicit type is now used. Previously, the column would have been
    dumped as an integer column.

  • When dumping unsigned integer columns in the schema dumper, add a
    column > 0 constraint in the dumped migration.

  • On Microsoft SQL Server, when updating a dataset with a limit,
    the limit is now respected.

  • When emulating offset using the ROW_NUMBER window function,
    do not require that the dataset be ordered. If an order is
    not provided, default to ordering on all of the columns in
    the dataset. If you want to override the default order used
    in such a case, you need to override the default_offset_order
    method for the dataset.

  • On SQLite, casting to Date/Time/DateTime now calls an SQLite
    date/datetime function instead of using a cast, as SQLite treats
    such a cast as a cast to integer.

  • When using JRuby 1.6 in ruby 1.9 mode and typecasting a time
    column, workaround a bug where Time#nsec is 0 even though
    Time#usec is not.

  • The odbc/mssql adapter now correctly handles the case where
    SCOPE_IDENTITY returns NULL after an insert.

  • bin/sequel now accepts multiple -l options for logging to multiple
    output files.

  • In addition to Sequel’s rigorous pre-push testing, Sequel now
    also uses TravisCI for continuous integration testing across
    a wider range of ruby implementations.

= Backwards Compatibility

  • The keys in the :key_hash entry passed to the :eager_loader proc
    are now method references instead of column references. For most
    associations, they are the same thing, but for associations using
    the :key_column/:primary_key_column/:left_primary_key_column
    options, the values could be different. If you were using one
    of those options and had a custom eager_loader, you should switch
    from indexing into the :key_hash option to just using the :id_map

  • The :key_hash entry passed to the :eager_loader proc is now no
    longer guaranteed to contain key maps for associations other than
    the one currently being eagerly loaded. Previously, it contained
    key maps for all associations that were being eagerly loaded. If
    you have a custom :eager_loader proc that accessed a key map for
    a separate association that was being loaded concurrently, you’ll
    now have to build the key map manually if it doesn’t exist.

  • If you previously explicitly specified an :eager_loader_key option
    when defining an association, you may need to change it so that it
    is a method reference instead of a column reference, or possibly
    just omit the option.

  • If you have a custom :eager_loader proc for an association where
    the default :eager_loader_key option references a method that
    the model does not respond to (or raises an exception), you may
    need to specify the :eager_loader_key=>nil option.

  • In the pg_auto_parameterize extension, String values are no longer
    automatically casted to text. This is because the default type of
    a string literal in PostgreSQL is unknown, not text. This makes it
    much less likely to require manual casts, but has the potential to
    break existing code relying on the automatic cast to text. As a
    work around, any query that can no longer be automatically
    parameterized after this query just needs to add manual casting
    to text.

  • Sequel now raises an exception if you attempt to clone associations
    with different types, except if one type is one_to_many and the
    other is one_to_one. Cloning from other types was usually a bug,
    and raising an exception early will make it much easier to track
    such bugs down.

  • When running the plugin/extension and PostgreSQL adapter specs,
    a json library is now required.

  • The json/postgres adapter array typecasting internals have been
    modified, if you were relying on the internals, you may need to
    update your code.

  • The pg_array extension internals changed significantly. PGArray
    no longer has any subclasses by default, as parsing is now done
    in separate objects. Anyone relying on the pg_array internals
    will need to update their code.

  • The postgres adapter no longer sets up type conversion of int2vector
    and money types, since in both cases the conversion was incorrect in
    most cases. These types will now be returned as strings. If you are
    relying on the conversion, you’ll need to add your own custom type