ANN: Sequel 3.9.0 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, Amalgalite, DataObjects,
    DB2, DBI, Firebird, Informix, JDBC, MySQL, ODBC, OpenBase, Oracle,
    PostgreSQL and SQLite3.

Sequel 3.9.0 has been released and should be available on the gem

New Features

  • The ConnectionPool classes were refactored from 2 separate
    classes to a 5 class hierarchy, with one main class and 4
    subclasses, one for each combination of sharding and threading.

    The primary reason for this refactoring is to make it so that
    the user doesn’t have to pay a performance penalty for sharding
    if they aren’t using it. A connection pool that supports sharding
    is automatically used if the :servers option is used when setting
    up the database connection.

    In addition, the default connection pool no longer contains
    the code to schedule future disconnections of currently allocated
    connections. The sharded connection pool must be used if that
    feature is desired.

    The unsharded connection pools are about 25-30% faster than the
    sharded versions.

  • An optimistic_locking plugin was added to Sequel::Model. This
    plugin implements a simple database-independent locking mechanism
    to ensure that concurrent updates do not override changes:

    class Person < Sequel::Model
    plugin :optimistic_locking
    p1 = Person[1]
    p2 = Person[1]



    raises Sequel::Plugins::OptimisticLocking::Error


    In order for this plugin to work, you need to make sure that the
    database table has a lock_version column (or other column you name
    via the lock_column class level accessor) that defaults to 0.

    The optimistic_locking plugin does not work with the
    class_table_inheritance plugin.

  • Dataset#unused_table_alias was added, which takes a symbol and
    returns either that symbol or a new symbol which can be used as
    a table alias when joining a table to the dataset. The symbol
    returned is guaranteed to not already be used by the dataset:

    DB[:test].unused_table_alias(:blah) # => :blah
    DB[:test].unused_table_alias(:test) # => :test_0

    The use case is when you need to join a table to a dataset, where
    the table may already be used inside the dataset, and you want
    to generate a unique alias:

    ds.join(, …)

  • The Sequel::ValidationFailed exception now has an errors accessor
    which returns the Sequel::Model::Errors instance with the
    validation errors. This can be helpful in situations where a
    generalized rescue is done where the model object reference is
    not available.

  • bin/sequel now works without an argument, which is useful for
    testing SQL generation (and not much else).

  • Support SELECT … INTO in the MSSQL adapter, using Dataset#into,
    which takes a table argument.

  • You can now provide your own connection pool class via the
    :pool_class option when instantiating the database.

Other Improvements

  • IN/NOT IN constructs with an empty array are now handled properly.

    DB[:table].filter(:id=>[]) # IN
    DB[:table].exclude(:id=>[]) # NOT IN

    Before, the IN construct would mostly work, other than some minor
    differences in NULL semantics. However, the NOT IN construct
    would not work. Sequel now handles the NOT IN case using an
    expression that evaluates to true.

  • If using an IN/NOT IN construct with multiple columns and a dataset
    argument, where multiple column IN/NOT IN support is emulated, a
    separate query is done to get the records, which is then handled
    like an array of values. This means that the following type of
    query now works on all tested databases:

    DB[:table1].filter([:id1, :id2]=>DB[:table2].select(:id1, :id2))

  • Schemas and aliases are now handled correctly when eager graphing.

  • Implicitly qualified symbols are now handled correctly in update
    statements, useful if you are updating a joined dataset and need
    to reference a column that appears in multiple tables.

  • The active_model plugin has been brought up to date with
    activemodel 3.0 beta (though it doesn’t work on edge).
    Additionally, the active_model plugin now requires active_model
    in order to use ActiveModel::Naming.

  • In the schema_dumper extension, always include the varchar limit,
    even if it is 255 columns (the default). This makes it so that
    PostgreSQL will use a varchar(255) column instead of a text column
    when restoring a schema dump of a varchar(255) column from another

  • You can now load adapters from outside the Sequel lib directory,
    now they just need to be in a sequel/adapters directory somewhere
    in the LOAD_PATH.

  • You can now load extensions from outside the Sequel lib directory
    using Sequel.extension. External extensions need to be in a
    sequel/extensions directory somewhere in the LOAD_PATH.

  • Using bound variables for limit and offset in prepared statements
    now works correctly.

  • Performance of prepared statements was improved in the native
    SQLite adapter.

  • The schema_dumper extension now passes the options hash from
    dump_*_migration to Database#tables.

  • In the single_table_inheritance plugin, qualify the sti_key column
    with the table name, so that subclass datasets can safely be joined
    to other tables having the same column name.

  • In the single_table_inheritance plugin, handle case where the
    sti_key value is nil or ‘’ specially, so that those cases
    always return an instance of the main model class. This fixes
    issues if constantize(nil) returns Object instead of raising
    an exception.

  • No longer use Date#to_s for literalization, always use ISO8601
    format for dates.

  • A couple lambdas which were instance_evaled were changed to procs
    for ruby 1.9.2 compatibility.

  • MSSQL emulated offset support was simplified to only use one
    subquery, and made to work correctly on ruby 1.9.

  • Emulate multiple column IN/NOT IN on H2, since it doesn’t handle
    all cases correctly.

  • ODBC timestamps are now handled correctly if the database_timezone
    is nil.

  • ArgumentErrors raised when running queries in the ODBC adapter are
    now raised as DatabaseErrors.

  • Attempting to use DISTINCT ON on SQLite now raises an error before
    sending the query to the database.

  • The options hash passed to the database connection method is no
    longer modified. However, there may be additional options
    present in Database#opts that weren’t specified by the options
    hash passed to the database connection method.

  • Make Dataset#add_graph_aliases handle the case where the dataset
    has not yet been graphed.

  • You can now provide an SQL::Identifier as a 4th argument to
    Dataset#join_table, and unsupported arguments are caught and an
    exception is raised.

  • The gem specification has been moved out of the Rakefile, so
    that the gem can now be built without rake, and works well with
    gem build and bundler.

  • The Rakefile no longer assumes the current directory is in the
    $LOAD_PATH, so it should work correctly on ruby 1.9.2.

  • All internal uses of require are now thread safe.

  • Empty query parameter keys in connection strings are now ignored
    instead of raising an exception.

  • The specs were changed so that you can run them in parallel.
    Previously there was a race condition in the migration extension

Backwards Compatibility

  • If you plan on using sharding at any point, you now must pass
    a :servers option when connecting to the database, even if it is
    an empty hash. You can no longer just call Database#add_servers

  • The connection_proc and disconnection_proc accessors were removed
    from the connection pools, so you can no longer modify the procs
    after the connection pool has been instantiated. You must now
    provide the connection_proc as the block argument when
    instantiating the pool, and the disconnection_proc via the
    :disconnection_proc option.

  • In the hash passed to Dataset#update, symbol keys with a double
    embedded underscore are now considerated as implicit qualifiers,
    instead of being used verbatim. If you have a column that includes
    a double underscore, you now need to wrap it in an SQL::Identifier
    or use a String instead.

  • The connection pools no longer convert non-StandardError based
    exceptions to RuntimeErrors. Previously, all of the common adapters
    turned this feature off, so there is no change for most users.

  • Sequel::ConnectionPool is now considered an abstract class and
    should not be instantiated directly. Use ConnectionPool.get_pool
    to return an instance of the appropriate subclass.

  • The Sequel::SingleThreadedPool constant is no longer defined.

  • The private Dataset#eager_unique_table_alias method was removed,
    use the new public Dataset#unused_table_alias method instead, which
    has a slightly different API.

  • The private Dataset#eager_graph_qualify_order method was removed,
    used Dataset#qualified_expression instead.

  • The private Sequel::Model class methods plugin_gem_location and
    plugin_gem_location_old have been removed.

  • Gems built with the rake tasks now show up in the root directory
    instead of the pkg subdirectory, and no tarball package is created.

Other News


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