= New Features

* Model#qualified_pk_hash has been added, which is similar to
  Model#pk_hash, but uses qualified keys.

* Dataset#distinct now accepts a virtual row block.

* Database#drop_view with :foreign=>true option now drops foreign
  tables on PostgreSQL.  Database#create_table with :foreign option
  is now reversible on PostgreSQL.

= Other Improvements

* Sequel::Model.cache_associations = false now skips the database's
  schema cache when loading the schema for a model.  This fixes
  some issues in environments that use code reloading.

* Database#create_table? and #create_join_table? no longer use
  IF NOT EXISTS if indexes are being created.

* Model.primary_key_hash and .qualified_primary_key_hash have been
  optimized.

* validates_unique in the validation_helpers plugin now uses a
  qualified primary key if the model's dataset is joined.  This fixes
  a case when the auto_validations and class_table_inheritance
  plugins are used together.

* Disconnect errors are now recognized in the postgres adapter when
  SSL is used for connecting.

* Empty string default values are no longer converted to nil default
  values on MySQL.

* Database#foreign_key_list now works correctly on Microsoft SQL
  Server 2005.