ANN: Sequel 2.10.0 Released

Sequel is a lightweight database access toolkit for Ruby.

  • Sequel provides thread safety, connection pooling and a concise DSL
    for constructing database queries and table schemas.
  • Sequel also includes a lightweight but 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, master/slave
    configurations, and database sharding.
  • Sequel makes it easy to deal with multiple records without having
    to break your teeth on SQL.
  • Sequel currently has adapters for ADO, DataObjects, DB2, DBI,
    Firebird, Informix, JDBC, MySQL, ODBC, OpenBase, Oracle, PostgreSQL
    and SQLite3.

Sequel 2.10.0 has been released and should be available on the gem
mirrors. The 2.10.0 release adds numerous improvements:

New Supported Adapters and Databases

  • A DataObjects adapter was added that supports PostgreSQL,
    MySQL, and SQLite. DataObjects is the underlying database
    library used by DataMapper, and has potential performance
    advantages by doing all typecasting in C.

  • A Firebird Adapter was added, it requires the modified Ruby
    Fb adapter found at GitHub - wishdev/fb: Firebird Extension Library for Ruby.

  • An H2 JDBC subadapter was added, based on the code used in JotBot.
    H2 is an embeddable Java database, and may be preferable to using
    SQLite on JDBC because SQLite requires native code.

New Core Features

  • Sequel now has database independent migrations. Before, column
    types in migrations were not translated per database, so it was
    difficult to set up a migration that worked on multiple databases.
    Sequel now accepts ruby classes as database types, in addition to
    symbols and strings. If a ruby class is used, it is translated
    to the most appropriate database type. Here is an example using
    all supported classes (with Sequel’s default database type):

    DB.create_table(:cats) do
    primary_key :id, :type=>Integer # integer
    String :a # varchar(255)
    column :b, File # blob
    Fixnum :c # integer
    foreign_key :d, :other_table, :type=>Bignum # bigint
    Float :e # double precision
    BigDecimal :f # numeric
    Date :g # date
    DateTime :h # timestamp
    Time :i # timestamp
    Numeric :j # numeric
    TrueClass :k # boolean
    FalseClass :l # boolean

    Type translations were tested on the PostgreSQL, MySQL, SQLite,
    and H2 databases. The default translations should work OK for
    most databases, but there will probably be a type or two that
    doesn’t work. Please send in a patch if Sequel uses a column type
    that doesn’t work on your database.

    Note that existing migrations still work fine, in most cases. If
    you were using strings or symbols for types before, they should
    still work. See the Backwards Compatibility section below for

    Also note that this doesn’t relate solely to migrations, as any
    database schema modification method that accepts types will
    accept one of the above classes.

  • A ton of internal work was done to better support databases that
    fold unqouted identifiers to uppercase (which is the SQL standard).
    Sequel now allows you to set a method to call on identifiers going
    both into and out of the database. The default is to downcase
    identifiers coming out, and upcase identifiers going in, though
    this is overridden by the PostgreSQL, MySQL, and SQLite adapters
    to not do anything (since they fold to lowercase by default).

    The settings are called identifier_input_method and
    identifier_output_method, and like most Sequel settings, they can
    be set globally, per database, or per dataset:

    Global (use uppercase in ruby and lowercase in the database)

    Sequel.identifier_input_method = :downcase
    Sequel.identifier_output_method = :upcase

    Per Database (use camelized names in the database, and

    underscored names in ruby)

    DB.identifier_input_method = :camelize
    DB.identifier_output_method = :underscore

    Per Dataset (obfuscate your database columns!)

    class String; def rot_13; tr(‘A-Za-z’, ‘N-ZA-Mn-za-m’) end end
    ds = DB[:table]
    ds.identifier_input_method = :rot_13
    ds.identifier_output_method = :rot_13

  • Schema parsing support was added to the JDBC adapter, using the
    JDBC metadata methods. This means that models that use the
    JDBC adapter will typecast data in their column setters and
    automatically select the correct primary key column(s). This is
    currently the only adapter that supports schema parsing when using
    an MSSQL or Oracle database.

  • Database#create_table now takes options, which you can use to
    specify a MySQL engine, charset, and/or collation. You can also
    set a default engine, charset, and collation for MySQL to use:

    Sequel::MySQL.default_engine = ‘InnoDB’
    Sequel::MySQL.default_charset = ‘utf8’
    Sequel::MySQL.default_collate = ‘utf8’

    The defaults will be used if the options are not provided. If a
    default engine is set, you can specify :engine=>nil to not use it
    (same goes for charset and collate).

  • The Sequel::DatabaseConnectionError exception class was added. It
    is raised by the connection pool if there is an error attempting
    to instantiate a database connection. Also, if the adapter returns
    nil instead of raising an error for faulty connection parameters,
    DatabaseConnectionError will be raised immediately, instead of the
    connection pool busy waiting until if gives up with a

  • Database#tables is now supported on the JDBC adapter, returning
    an Array of table name symbols.

  • Sequel now converts the following Java types returned by the JDBC
    adapter into ruby types: Java::JavaSQL::Timestamp,
    Java::JavaSQL::Time, Java::JavaSQL::Date,
    Java::JavaMath::BigDecimal, and Java::JavaIo::BufferedReader.

  • When using the PostgreSQL adapter with the postgres-pr driver,
    Sequel will use a custom string escaping routine unless
    force_standard_strings = false. This means that using Sequel’s
    defaults, postgres-pr will correctly escape strings now.

  • The SQLite adapter now returns float, real, and double precision
    columns as Floats.

  • The SQLite adapter logs beginning, committing, and rolling back

  • Sequel now has an internal version (before, the only way to tell
    the version was to look at the gem being used). It is accessible
    at Sequel.version.

New Model Features

  • A new validates_not_string validation was added for Sequel Models.
    It is intended to be used with the raise_on_typecast_failure =
    false setting. In this case, for a non-string database column,
    if there is a string value when the record is going to be
    saved, it is due to the fact that Sequel was not able to typecast
    the given data correctly (so it is almost certainly not valid).
    This should make Sequel easier to use with web applications.

  • An :allow_missing validation option was added to all standard
    validations. This option skips the validation if the attribute
    is not in the object’s values. It is different from :allow_nil,
    which will skip the value if it is present but nil in the values.
    The intended use case for this option is when the database provides
    a good default. If the attribute is not present in values, the
    database will use its default. If the attribute is present in
    the values but equals nil, Sequel will attempt to insert it into
    the database as a NULL value, instead of using the database’s
    default. If you don’t want Sequel to insert a NULL value in the
    database, but you want the database to provide the default, this
    is the option to use.

  • validates_each now accepts :allow_nil and :allow_blank options,
    so it is easier to create custom validations with the same options
    as the standard validations.

  • Before_* hooks now run in the reverse order that they were added.
    The purpose of hooks is to wrap existing functionality, and making
    later before_* hooks run before previous before_* hooks is the
    correct behavior.

  • You can now add you own hook types, via Model.add_hook_type. This
    is intended for plugin use. All of the standard hooks are now
    implemented using this method.

  • The value of new? in a after_save hook now reflects the
    previous state of the model (so true for a create and false for an
    update), instead of always being false. This makes it easier
    to have a complex after_save hook that still needs to
    differentiate between a newly created record and an updated record,
    without having to add separate after_create and after_update

  • The value of changed_columns in an after_update hook now reflects
    the value before the update occurred, instead of usually being
    empty. Previously, to have this functionality, you generally had
    to save the value to an instance variable in a before_update hook
    so you could reference it in the after_update hook.

Other Improvements

  • Sequel now longer overwrites the following Symbol instance methods
    when running on ruby 1.9: [], <, <=, >, and >=. One of Sequel’s
    principals is that it does not override methods defined by ruby,
    and now that ruby 1.9 defines the above methods on Symbol, Sequel
    shouldn’t be overwriting them.

    Sequel already provides a way to work around this issue when
    another library adds the same methods to Symbol that Sequel does.
    For example, you need to change the following:

    dataset.filter(:number > 1)
    dataset.filter(:number >= 2)
    dataset.filter(:name < ‘M’)
    dataset.filter(:name <= ‘I’)


    dataset.filter{|o| o.number > 1}
    dataset.filter{|o| o.number >= 2}
    dataset.filter{|o| < ‘M’}
    dataset.filter{|o| <= ‘I’}
    dataset.filter{|o| o.is_bool(:x)}

    The argument provided to the block is a Sequel::SQL::VirtualRow.
    This class uses method_missing so that any methods called on it
    return Sequel::SQL::Identifiers (if no arguments are provided)
    or Sequel::SQL::Function (if arguments are provided).

    If you were using one of the above symbol methods outside of a
    filter, you can to call sql_string, sql_number, or sql_function
    on the symbol. So the following would also work:

    dataset.filter(:number.sql_number > 1)
    dataset.filter(:number.sql_number >= 2)
    dataset.filter(:name.sql_string < ‘M’)
    dataset.filter(:name.sql_number <= ‘I’)

    Using the block argument makes for a nicer API, though, so I
    recommend using it when possible.

    Note that if you are running ruby 1.8 or jruby without the --1.9
    flag, you don’t need to worry. If you are running ruby 1.9 or
    jruby --1.9, or you plan to at some point in the future, you
    should inspect your code for existing uses of these methods.
    Here are a couple command lines that should find most uses:

    Find :symbol[]

    egrep -nr ‘:[’'‘"]?[a-zA-Z_0-9]*[’'‘"]?[’ *

    Find :symbol (<|>|<=|>=)

    egrep -nr ‘[^:]:[’'‘"]?[a-zA-Z_0-9]*[’'‘"]? *[<>]=?’ *

  • Database#quote_identifiers now affects future schema modifications
    when using the database. Previous, it only affected future
    schema modifications if a schema modification method had not yet
    been called.

  • Literalization of Times and DateTimes is now correct when using the
    MySQL JDBC subadapter.

  • Literalization of Blobs is now correct when using the PostgreSQL
    JDBC subadapter.

  • Index and table names are quoted when creating indices in the
    PostgreSQL adapter.

  • Dataset#delete was changed in the SQLite adapter to add a
    where clause that is always true, instead of doing an explicit
    count first and the deleting. This is simpler, though it
    could potentially have performance implications.

  • The sequel command line tool now supports symbol keys and unnested
    hashes in YAML files, so it should work with Merb’s database.yml.
    It also includes the error class in the case of an error.

  • The integration type tests were greatly expanded. Generally,
    running the integration tests is a good way to determine how well
    your database is supported.

  • Dataset#quote_identifier now returns LiteralStrings as-is, instead
    of treating them as regular strings.

  • Sequel no longer modifies the MySQL::Result class when using the
    MySQL adapter.

Backwards Compatibilty

  • If you were previously using a database that returned uppercase
    identifiers, it will probably return lowercase identifiers by
    default now. To get back the old behavior:

    DB.identifier_output_method = nil

  • The module hierarchy under Sequel::SQL has changed. Now,
    modules do not include other modules, and the following modules
    were removed since they would have been empty after removing
    the modules they included: Sequel::SQL::SpecificExpressionMethods
    and Sequel::SQL::GenericExpressionMethods.

  • Sequel no longer assumes the public schema by default when
    connecting to PostgreSQL. You can still set the default
    schema to use (even to public).

  • The ability to load schema information for all tables at once
    was removed from the PostgreSQL adapter. While it worked, it had
    some issues, and it was difficult to keep it working when some
    new features were used. This ability wasn’t exposed to the user,
    and was purely an optimization. If you have any code like:


    by itself after the Database object was instantiated, you should
    remove it.

  • The Database#primary_key API changed in the PostgreSQL shared
    adapter, it now accepts an options hash with :server and :conn keys
    instead of a server symbol. Also, quite a few private Database
    instance methods changed, as well as some constants in the

  • It is possible that some migrations will break, though it is
    unlikely. If you were using any of the classes mentioned above
    as a method inside a migration, it might be broken. However,
    since String, Float, and Integer wouldn’t have worked as methods
    before, it is unlikely that anyone used this.

  • The meaning of #String, #Integer, and #Float inside
    Sequel::SQL::Generator (i.e. inside a Database#create_table
    block) has changed. Before, these used to call private Kernel
    methods, now, they set up columns with the appropriate database

  • The Database#lowercase method in the DBI adapter was removed,
    as its use case is now met by the identifier_output_method support.

  • Database#uri is now aliased explicitly via a real method, to
    allow for easier subclassing.

  • You can no longer pass nil as the second argument to


Very nice, congrats. And a very nice release announcement too :slight_smile:

Jeremy E. wrote:

Sequel 2.10.0 has been released and should be available on the gem
mirrors. The 2.10.0 release adds numerous improvements:

Very cool! Thanks for the hard work.

James B. - Wicked Cool Coding - Playing with Better Toys - Ruby Help & Documentation - The Ruby Store for Ruby Stuff