= New Features

* The serialization plugin can now support custom serialization
  formats, by supplying a serializer/deserializer pair of
  callable objects.  You can also register custom deserializers
  via Sequel::Plugins::Serialization.register_format, so that
  they can be referenced by name.  Example:
  
    Sequel::Plugins::Serialization.register_format(:reverse,
      lambda{|v| v.reverse},
      lambda{|v| v.reverse})
    class User < Sequel::Model
      serialize_attributes :reverse, :password
    end

* Dataset#import and #multi_insert now support a
  :return=>:primary_key option.  When this option is used, the
  methods return an array of primary key values, one for each
  inserted row.  Usage of this option on MySQL requires that a
  separate query be issued per row (instead of the single
  query for all rows that MySQL would usually use).
  
* PostgreSQL can now use Dataset#returning in conjunction with
  import/multi_insert to set a custom column to return.
  
* Microsoft SQL Server can now use Dataset#output in conjection with
  import/multi_insert to set a custom column to return.
  
* Dataset#import and #multi_insert now respect a :server option to
  set the server/shard on which to execute the queries.
  Additionally, options given to this method are also passed to
  Dataset#transaction.

* Dataset#insert_multiple now returns an array of inserted primary
  keys.

* Model.def_column_alias has been added to make it easy to create
  alias methods for columns.  This is useful if you have a legacy
  database and want to create friendly method names for the
  underlying columns.  Note that this alias only affects the setter
  and getter methods.  This does not affect the dataset level, so you
  still need to use the actual column names in dataset filters.

* many_to_one associations can now have the same name as the related
  foreign key column, using the :key_column option.  Use of this
  feature is not recommended, as it is much better to either rename
  the column or rename the association.  Here's an example of usage:
  
    # Example schema:
    #  albums           artists
    #   :id        /-->  :id
    #   :artist --/      :name
    #   :name
    class Album < Sequel::Model
      def_column_alias(:artist_id, :artist)
      many_to_one :artist, :key_column=>:artist
    end

* The mock adapter can now mock out database types, by providing a
  shared adapter name as the host (e.g. mock://postgres).  This
  emulation is not perfect, but in most cases it allows you to see
  what SQL Sequel would generate on a given database without needing
  to install the required database driver.

* Sequel now supports creating full text indexes on Microsoft SQL
  Server.  Before using it, you must have previously setup a default
  full text search catalog, and you need to provide a :key_index
  option with an index name symbol.
  
* Dataset#group_rollup and #group_cube methods have been added for
  GROUP BY ROLLUP and GROUP BY CUBE support.  These features are in
  a recent SQL standard, and they are supported to various degrees on
  Microsoft SQL Server, DB2, Oracle, MySQL, and Derby.

* Dataset#full_text_search on Microsoft SQL Server now supports
  multiple search terms.
  
* The jdbc adapter now supports a :login_timeout option, giving the
  timeout in seconds.

= Other Improvements

* Dataset#exists can now be used with prepared statement
  placeholders.

* Dataset#full_text_search can now be used with prepared statement
  placeholders on PostgreSQL, MySQL, and Microsoft SQL Server.
  
* If tables from two separate schema are detected when parsing the
  schema for a table on PostgreSQL, an error is now raised.
  Previously, no error was raised, which led to weird errors later,
  such as duplicate columns in a model's primary_key.

* RETURNING is now supported with UPDATE/DELETE on PostgreSQL 8.2+.
  Previously, Sequel only supported it on 9.1+, but PostgreSQL
  introduced support for it in 8.2.

* The shared postgres adapter now correctly handles the return value
  for Dataset#insert if you provide a separate column array and value
  array on PostgreSQL < 8.2.
  
* Handle case in the PostgreSQL adapter where the server version
  cannot be determined via a query.
  
* H2 clob types are now treated as string instead of as blob.
  Treating clob as blob breaks on H2, as it doesn't automatically
  hex-unescape the input for clobs as it does for blobs.
  
* Dataset#empty? now works correctly when the dataset has an offset
  and offset support is being emulated.

* The mock adapter no longer defaults to downcasing identifiers on
  output.

= Backwards Compatibility

* Dataset#exists now returns a PlaceholderLiteralString instead of a
  LiteralString, which could potentially break some code.  If you
  would like a String returned, you can pass the returned object to
  Dataset#literal:
  
    dataset.literal(dataset.exists)

* Dataset#from no longer handles :a__b__c___d as "a.b.c AS d".  This
  was not the intended behavior, and nowhere else in Sequel is a
  symbol treated that way.  Now, Dataset#from is consistent with the
  rest of Sequel, using "a.b__c AS d".  This should only affect
  people in very rare cases, as most databases don't use three level
  qualified tables.  One exception is Microsoft SQL Server, which can
  use three level qualified tables for cross-database access.
  
* Previously, Dataset#insert_multiple returned an array of hashes, now
  it returns an array of primary key values.

* Dataset#EXRACT_CLOSE in the shared sqlite adapter has been renamed to
  Dataset#EXTRACT_CLOSE.
  
* Dataset::StoredProcedureMethods::SQL_QUERY_TYPE and
  Dataset::ArgumentMapper::SQL_QUERY_TYPE constants have been removed,
  as have related sql_query_type private methods.

* The serialization plugin was significantly refactored.
  Model.serialization_map now contains a callable object instead of a
  Symbol, and Model.serialization_format has been removed.
  Model.define_serialized_attribute_accessors private method now takes
  two callable objects before the columns, instead of a single symbol.
