ANN: Sequel 3.0.0 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 3.0.0 has been released and should be available on the gem
mirrors. The 3.0.0 release adds numerous improvements:

Deprecated Methods/Features Removed

Methods and features that were deprecated in 2.12.0 have been removed
in 3.0.0. Many features were moved into plugins or extensions, so in
many cases you just need to require an extension or use Model.plugin
and not make any changes to your code. See the 2.12.0 release notes
for the list of methods/features deprecated in 2.12.0.

If you are upgrading from a previous 2.x release, please upgrade to
2.12.0 first, fix your code to remove all deprecation warnings, and
then upgrade to 3.0.0.

New Adapter

  • Sequel now has an Amalgalite adapter. Amalgalite is a ruby
    extension that embeds SQLite without requiring a separate SQLite
    installation. The adapter is functionality complete but
    significantly slower than the native SQLite adapter.

New Features

  • The JDBC, PostgreSQL, MySQL, and SQLite adapters all now have a
    Database#indexes method that returns indexes for a given table:

    => {:songs_name_index=>{:unique=>true, :columns=>[:name]},
    :songs_lyricid_index=>{:unique=>false, :columns=>[:lyricid]}}

  • A schema_dumper extension was added to Sequel. It supports dumping
    the schema of a table (including indexes) as a string that can be
    evaluated in the context of a Database object to create the table.
    It also supports dumping all tables in the database as a string
    containing a Migration subclass that will rebuild the database.

    require ‘sequel/extensions/schema_dumper’

    The :same_db option causes Sequel to not translate column types
    to generic column types. By default, the migration created will
    use generic types so it will run on other databases. However, if
    you only want to support a single database, using the :same_db
    option will make the migration use the exact database type parsed
    from the database.

    The :indexes=>false option causes indexes not be included in the
    migration. The dump_indexes_migration can be used to create a
    separate migration with the indexes. This can be useful if you
    plan on loading a lot of data right after creating the tables,
    since it is faster to add indexes after the data has been added.

  • Using options with the generic database types is now supported to
    a limited extent. For example, the following code now works:

    DB.create_table(:table) do
    String :a, :size=>50 # varchar(50)
    String :b, :text=>true # text
    String :c, :fixed=>true, :size=>30 # char(30)
    Time :ts # timestamp
    Time :t, :only_time=>true # time

  • Using Dataset#filter and related methods with multiple arguments
    now works much more intuitively:


    dataset.filter(:a, :b=>1) # a IS NULL AND (b = 1) IS NULL


    dataset.filter(:a, :b=>1) # a AND b = 1

  • You can now create temporary tables by passing the :temp=>true
    option to Database#create_table.

  • The Oracle shared adapter now supports emulation of
    autoincrementing primary keys by creating a sequence and a trigger,
    similar to how the Firebird adapter works.

  • The Database#database_type method was added that returns a symbol
    specifying the database type being used. This can be different
    than Database.adapter_scheme if you are using an adapter like
    JDBC that allows connecting to multiple different types of

  • Database#drop_index and related methods now support an options
    hash that respects the :name option, so they can now be used to
    drop an index that doesn’t use the default index name.

  • The PostgreSQL shared adapter now supports a
    Database#reset_primary_key_sequence method to reset the
    primary key sequence for a given table, based on code from

  • SQL::QualifiedIdentifiers can now be qualified, allowing you to do:


  • Using the :db_type=>‘mssql’ option with the DBI adapter will now
    load the MSSQL support.

  • The MySQL shared adapter now supports Dataset#full_text_sql, which
    you can use in queries like the following:*, ds.full_text_sql(:column, ‘value’).as(:ft))

Other Improvements

  • Sequel will now release connections from the connection pool
    automatically if they are held by a dead thread. This can happen
    if you are using MRI 1.8 and you are heavily multithreaded or
    you call Thread#exit! or similar method explicitly. Those methods
    skip the execution of ensure blocks which normally release the
    connections when the threads exit.

  • Model#save will now always use the same server when refreshing data
    after an insert. This fixes an issue when Sequel’s master/slave
    database support is used with models.

  • SQL Array references are now quoted correctly, so code like this
    now works:


  • The PostgreSQL shared adapter now handles sequences that need to be
    quoted correctly (previously these were quoted twice).

  • String quoting on Oracle no longer doubles backslashes.

  • Database#count now works correctly when used on MSSQL when using
    an adapter that doesn’t handle unnamed columns.

  • Full text searching in the MySQL adapter now works correctly when
    multiple search terms are used.

  • Altering a column’s name, type, default, or NULL/NOT NULL status
    on MySQL now keeps other relevent column information. For example,
    if you alter a column’s type, it’ll keep an existing default. This
    functionality isn’t complete, there may be other column information
    that is lost.

  • Fix creation of an index with a given type on MySQL, since MySQL’s
    documentation lies.

  • The schema parser now handles decimal types with size specifiers,
    fixing use on MySQL.

  • Dataset#quote_identifier now works correctly when given an
    SQL::Identifier. This allows you to do:{sum(hours).as(hours)}

Backwards Compatibility

  • Sequel will now use instance_eval on all virtual row blocks without
    an argument. This can lead to much nicer code:

    dataset.filter{(number > 10) & (name > ‘M’)}

    WHERE number > 10 AND name > ‘M’

    2.12.0 raised a deprecation warning if you used a virtual row block
    without an argument and you hadn’t set
    Sequel.virtual_row_instance_eval = true.

  • Dataset#exclude now inverts the given argument, instead of negating
    it. This only changes its behavior if it is called with a hash or
    array of all two pairs that have more than one element.


    dataset.exclude(:a=>1, :b=>1) # a != 1 AND b != 1


    dataset.exclude(:a=>1, :b=>1) # a != 1 OR b != 1

    This was done for consistency, since exclude would only negate a
    hash if it was given an argument, it would invert the same hash
    if you used a block:


    dataset.exclude{{:a=>1, :b=>1}} # a != 1 OR b != 1

    If you want the previous behavior,
    change the code to the following:

    dataset.filter({:a=>1, :b=>1}.sql_negate)

  • As noted above, the methods/features deprecated in 2.12.0 were

  • The private Dataset#select_*_sql methods now only take a single
    argument, the SQL string being built.

  • Dataset#from when called without arguments would previously cause an
    error to be raised when the SQL string is generated. Now it causes
    no FROM clause to be used, similar to how Dataset#select with no
    arguments causes SELECT * to be used.

  • The internals of the generic type support and the schema generators
    were changed significantly, which could have some fallout in terms
    of old migrations breaking if they used the generic types and were
    relying on some undocumented behavior (such as using Integer as a
    type with the :unsigned option).

  • The Firebird adapter no longer translates the text database
    specific type. Use the following instead:

    String :column, :text=>true

  • The MySQL shared adapter used to use the timestamp type for Time,
    now it uses datetime. This is because the timestamp type cannot
    represent everything that the ruby Time class can represent.

  • Metaprogramming#metaattr_accessor and #metaattr_reader methods were

  • Dataset#irregular_function_sql was removed.


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