Class: DeltaForce::ChangeProxy

Inherits:
Object
  • Object
show all
Defined in:
lib/delta_force/change_proxy.rb

Instance Attribute Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(klass) ⇒ ChangeProxy

Returns a new instance of ChangeProxy.



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# File 'lib/delta_force/change_proxy.rb', line 7

def initialize(klass)
  @klass = klass
end

Instance Attribute Details

#klass ⇒ Object (readonly)

Returns the value of attribute klass.



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# File 'lib/delta_force/change_proxy.rb', line 5

def klass
  @klass
end

Instance Method Details

#values(*value_fields) ⇒ Object Also known as: value 



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# File 'lib/delta_force/change_proxy.rb', line 11

def values(*value_fields)
  options = value_fields.extract_options!.symbolize_keys

  partition_key = options[:by].to_s
  partition_column = "#{table_name}.#{partition_key}"
  id_column = "#{table_name}.id"

  period_field_name = options[:over].to_s
  period_column = "#{table_name}.#{period_field_name}"

  scope_name = options[:scope_name] || default_scope_name(value_fields, options)

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

  value_expressions = value_fields.collect do |value_field|
    value_field_name = value_field.to_s
    value_column = "#{table_name}.#{value_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.flatten

  klass.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},
    #{value_expressions.join ','}
  "

  value_fields.each do |value_field|
    klass.class.send :define_method, "#{value_field}_by_#{options[:by].to_s}_as_of_#{options[:over].to_s}" do |period|
      Hash[
        scoped(
          :select => "distinct #{partition_column},
            first_value(#{table_name}.#{value_field.to_s}) over #{window} as #{value_field.to_s}",
          :conditions => [ "#{period_column} <= ?", period]
        ).index_by(&partition_key.to_sym).map{|k,v| [k, v[value_field]]}
      ]
    end
  end
end