= New Features

* The defaults_setter plugin now supports a :cache option, which
  will cache default values in the model object's values hash:

    Model.plugin :defaults_setter
    o = Model.new
    o.column # => 1 # default value
    o.values # => {}

    Model.plugin :defaults_setter, cache: true
    o = Model.new
    o.column # => 1 # default value
    o.values # => {:column => 1}

* The pg_array extension now sets a :callable_default schema entry
  for recognized empty array defaults.

* The pg_hstore extension now sets a :callable_default schema entry
  for recognized empty hstore defaults.

* The pg_json extension now sets a :callable_default schema entry for
  recognized empty json/jsonb array/hash defaults. 

* The pg_inet extension now sets a :ruby_default schema entry for
  recognized inet/cidr defaults.

* The pg_range extension now sets a :ruby_default schema entry for
  recognized range defaults.

* The defaults_setter plugin will now give preference to a
  :callable_default schema entry over a :ruby_default schema entry.
  Combined with the other changes listed above, this makes default
  values recognized by the pg_array, pg_hstore, and pg_json extensions
  work well if the defaults_setter :cache option is also used.

= Other Improvements

* The modification_detection plugin no longer breaks column change
  detection for new objects.

* Database#copy_table in the postgres adapter now handles errors that
  occur when processing rows.  Previously, an exception could be
  raised on the next query in that case.

* The results of the changed_columns method are now cached in many
  places internally where they are called in a loop.  This results
  in better performance, especially if the modification_detection or
  serialization_modification_detection plugins are used.

= Backwards Compatibility

* The pg_interval extension now sets a :ruby_default schema entry for
  recognized interval defaults to the same value Sequel would return
  if the default value was returned.  Previously, Sequel would use a
  string in the :ruby_schema schema value.

* String values in hashes returned by Database#schema are now frozen
  to prevent possible thread-safety issues and issues with
  unintentional modification of a shared string.  The hashes
  themselves are not frozen and can still be modified.