Module: DeltaForce::ClassMethods

Defined in:
lib/delta_force/class_methods.rb

Instance Method Summary collapse

Instance Method Details

#calculates_changes_in(value_field_name, options = {}) ⇒ Object 



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# File 'lib/delta_force/class_methods.rb', line 10

def calculates_changes_in(value_field_name, options = {})
  options = options.symbolize_keys

  value_field_name = value_field_name.to_s

  partition_field_name = options[:partition_by]
  partition_column = "#{table_name}.#{partition_field_name.to_s}"

  value_column = "#{table_name}.#{value_field_name}"
  id_column = "#{table_name}.id"

  period_field_name = options[:period] || 'period'
  period_column = "#{table_name}.#{period_field_name}"

  scope_name = "changes_in_#{value_field_name}".to_sym 

  window = "
    (
       PARTITION BY #{partition_column}
       ORDER BY #{period_column} DESC, #{id_column} DESC ROWS
       BETWEEN UNBOUNDED PRECEDING AND UNBOUNDED FOLLOWING
    )"

  named_scope scope_name, :select => "distinct #{partition_column},
    last_value(#{period_column}) over #{window} as opening_#{period_field_name},
    first_value(#{period_column}) over#{window} as closing_#{period_field_name},
    last_value(#{value_column}) over #{window} as opening_#{value_field_name},
    first_value(#{value_column}) over #{window} as closing_#{value_field_name}
    "
end

#tracks_changes_over_time {|DeltaForce::ChangeProxy.new(self)| ... } ⇒ Object

Yields:



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# File 'lib/delta_force/class_methods.rb', line 6

def tracks_changes_over_time
  yield DeltaForce::ChangeProxy.new(self)
end