New Features
------------

* Common table expressions (CTEs) are now supported.  CTEs use the
  SQL WITH clause, and specify inline views that queries can use.
  They also support a recursive mode, where the CTE can recursively
  query its own output, allowing you do do things like load all
  branches for a given node in a plain tree structure.
  
  The standard with takes an alias and a dataset:
  
    DB[:vw].with(:vw, DB[:table].filter{col < 1})
    # WITH vw AS (SELECT * FROM table WHERE col < 1)
    # SELECT * FROM vw
    
  The recursive with takes an alias, a nonrecursive dataset, and a
  recursive dataset:
    
    DB[:vw].with_recursive(:vw,
      DB[:tree].filter(:id=>1),
      DB[:tree].join(:vw, :id=>:parent_id).
                select(:vw__id, :vw__parent_id))
    # WITH RECURSIVE vw AS (SELECT * FROM tree
    #     WHERE (id = 1)
    #     UNION ALL
    #     SELECT vw.id, vw.parent_id
    #     FROM tree
    #     INNER JOIN vw ON (vw.id = tree.parent_id))
    # SELECT * FROM vw

  CTEs are supported by Microsoft SQL Server 2005+, DB2 7+,
  Firebird 2.1+, Oracle 9+, and PostgreSQL 8.4+.
  
* SQL window functions are now supported, and a DSL has been added to
  ease their creation.  Window functions act similarly to aggregate
  functions but operate on sliding ranges of rows.
  
  In virtual row blocks (blocks passed to filter, select, order, etc.)
  you can now provide a block to method calls to change the default
  behavior to create functions that weren't possible previously.  The
  blocks aren't called, but their presence serves as a flag.
  
  What function is created depends on the arguments to the method:
  
  * If there are no arguments, an SQL::Function is created with the
    name of method used, and no arguments.  Previously, it was not
    possible to create functions without arguments using the virtual
    row block DSL.  Example:
    
      DB.dataset.select{version{}} # SELECT version()
    
  * If the first argument is :*, an SQL::Function is created with a
    single wildcard argument (*).  This is mostly useful for count:
    
      DB[:t].select{count(:*){}} # SELECT count(*) FROM t
    
  * If the first argument is :distinct, an SQL::Function is created
    with the keyword DISTINCT prefacing all remaining arguments. This
    is useful for aggregate functions such as count:
    
      DB[:t].select{count(:distinct, col1){}}
      # SELECT count(DISTINCT col1) FROM t
    
  * If the first argument is :over, the second argument, if provided,
    should be a hash of options to pass to SQL::Window.  The options
    hash can also contain :*=>true to use a wildcard argument as the
    function argument, or :args=>... to specify an array of arguments
    to use as the function arguments.

      DB[:t].select{rank(:over){}} # SELECT rank() OVER ()
      DB[:t].select{count(:over, :*=>true){}} # SELECT count(*) OVER ()
      DB[:t].select{sum(:over, :args=>col1,
                    :partition=>col2, :order=>col3){}}
      # SELECT sum(col1) OVER (PARTITION BY col2 ORDER BY col3)
      
  PostgreSQL also supports named windows.  Named windows can be
  specified by Dataset#window, and window functions can reference
  them using the :window option.
  
* Schema information for columns now includes a :ruby_default entry
  which contains a ruby object that represents the default given by
  the database (which is stored in :default).  Not all :default
  entries can be parsed into a :ruby_default, but if the
  schema_dumper extension previously supported it, it should work.

* Methods to create compound datasets (union, intersect, except), now
  take an options hash instead of a true/false flag.  The previous
  API is still supported, but switching to specifying the ALL setting
  using :all=>true is recommended.
  
  Additionally, you can now set :from_self=>false to not wrap the
  returned dataset in a "SELECT * FROM (...)".
  
* Dataset#ungraphed was added that removes the graphing information
  from the dataset.  This allows you to use Dataset#graph for the
  automatic aliasing, or #eager_graph for the automatic aliasing and
  joining, and then remove the graphing information so that the
  resulting objects will not be split into subhashes or associations.

* There were some introspection methods added to Dataset to describe
  which capabilities that dataset does or does not support:
  
    supports_cte?
    supports_distinct_on?
    supports_intersect_except?
    supports_intersect_except_all?
    supports_window_functions?

  In addition to being available for the user to use, these are also
  used internally, so attempting to use a CTE on a dataset that
  doesn't support it will raise an Error.

* Dataset#qualify was added, which is like qualify_to with a default
  of first_source.

  Additionally, qualify now affects PlaceholderLiteralStrings.  It
  doesn't scan the string (as Sequel never attempts to parse SQL),
  but if you provide the column as a symbol placeholder argument, it
  will qualify it.
  
* You can now specify the table and column Sequel::Migrator will use
  to record the current schema version.  The new Migrator.run method
  must be used to use these new options.
  
* The JDBC adapter now accepts :user and :password options, instead
  of requiring them to be specified in the connection string and 
  handled by the JDBC driver.  This should allow connections to
  Oracle using the Thin JDBC driver.
  
* You can now specify the max_connections, pool_timeout, and
  single_threaded settings directly in the connection string:
  
    postgres:///database?single_threaded=t
    postgres:///database?max_connections=10&pool_timeout=20

* Dataset#on_duplicate_key_update now affects Dataset#insert when
  using MySQL.

* You can now specify the :opclass option when creating PostgreSQL
  indexes.  Currently, this only supports a single operator class
  for all columns.  If you need different operator classes per
  column, please post on sequel-talk.
  
* Model#autoincrementing_primary_key was added and can be used if
  the autoincrementing key isn't the same as the primary key.  The
  only likely use for this is on MySQL MyISAM tables with composite
  primary keys where only one of the composite parts is
  autoincrementing.

* You can now use database column values as search patterns and
  specify the text to search as a String or Regexp:
  
    String.send(:include, Sequel::SQL::StringMethods)
    Regexp.send(:include, Sequel::SQL::StringMethods)

    'a'.like(:x)  # ('a' LIKE x)
    /a/.like(:x)  # ('a' ~ x)
    /a/i.like(:x) # ('a' ~* x)
    /a/.like(:x, 'b') # (('a' ~ x) OR ('a' ~ 'b'))

* The Dataset#dataset_alias private method was added.  It can be
  overridden if you have tables named t0, t1, etc., and want to make
  sure the default dataset aliases that Sequel uses do not clash
  with existing table names.
  
* Sequel now raises an Error if you call Sequel.connect with
  something that is not a Hash or String.
  
* bin/sequel now accepts a -N option to not test the database
  connection.
  
* An opening_databases.rdoc file was added to the documentation
  directory, which should be a good introduction for new users about
  how to set up your Database connection.

Other Improvements
------------------

* MySQL native adapter SELECT is much faster than before, up to 75%
  faster.

* JDBC SELECT is about 10% faster than before.  It's still much
  slower than the native adapters, due to conversion issues.

* bin/sequel now works with a YAML file on ruby 1.9.

* MySQL foreign key table constraints have been fixed.

* Database#indexes now works on PostgreSQL if the schema used is a
  Symbol.  It also works on PostgreSQL versions all the way back to
  7.4.

* Graphing of datasets with dataset sources has been fixed.

* Changing a columns name, type, or NULL status on MySQL now
  supports a much wider selection of column defaults.
  
* The stored procedure code is now thread-safe.  Sequel is
  thread-safe in general, but due to a bug the previous stored 
  procedure code was not thread-safe.

* The ODBC adapter now drops statements automatically instead of
  requiring the user to do so manually, making it more similar
  to other adapters.

* The single_table_inheritance plugin no longer overwrites the STI
  field if the field already has a value.  This allows you to use
  create in the generic class to insert a value that will be
  returned as a subclass:
  
    Person.create(:kind => "Manager")
    
* When altering colums on MySQL, :unsigned, :elements, :size and other
  options given are no longer ignored.

* The PostgreSQL shared adapter's explain and analyze methods have
  been fixed, they had been broken in 3.0.
  
* Parsing of the server's version is more robust on PostgreSQL.
  It should now work correctly for 8.4 and 8.4rc1 type versions.

Backwards Compatibility
-----------------------

* Dataset#table_exists? has been removed, since it never worked
  perfectly.  Use Database#table_exists? instead.
  
* Model.grep now calls Dataset#grep instead of Enumerable#grep.
  If you are using Model.grep, you need to modify your application.

* The MSSQL shared adapter previously used the :with option for
  storing the NOLOCK setting of the query.  That option has been
  renamed to :table_options, since :with is now used for CTEs.
  This should not have an effect unless you where using the option
  manually.

* Previously, providing a block to a method calls in virtual row
  blocks did not change behavior, where now it causes a different
  code path to be used.  In both cases, the block is not evaluated,
  but that may change in a future version.
  
* Dataset#to_table_reference protected method was removed, as it was
  no longer used.
  
* The pool_timeout setting is now converted to an Integer, so if you
  used to pass in a Float, it no longer works the same way.
  
* Most files in adapters/utils have been removed, in favor of 
  integrating the code directly into Database and Dataset.  If you
  were previously checking for the UnsupportedIntersectExcept or
  related modules, use the Dataset introspection methods instead
  (e.g. supports_intersect_except?).
  
* If you were using the ODBC adapter and manually dropping returned
  statements, you should note that now statements are dropped
  automatically, and the execute method doesn't return a statement
  object.
  
* The MySQL adapter on_duplicate_key_update_sql is now a private
  method.
  
* If you were modifying the :from dataset option directly, note that
  Sequel now expects this option to be preprocessed.  See the new
  implementation of Dataset#from for an idea of the changes
  required.
  
* Dataset#simple_select_all? now returns false instead of true for a
  dataset that selects from another dataset.
