Module: FromSetOperator

Defined in:
app/models/concerns/from_set_operator.rb

Instance Method Summary collapse

Instance Method Details

#define_set_operator(operator) ⇒ Object

Define a high level method to more easily work with the SQL set operations of UNION, INTERSECT, and EXCEPT as defined by Gitlab::SQL::Union, Gitlab::SQL::Intersect, and Gitlab::SQL::Except respectively.



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# File 'app/models/concerns/from_set_operator.rb', line 7

def define_set_operator(operator)
  method_name = 'from_' + operator.name.demodulize.downcase
  method_name = method_name.to_sym

  raise "Trying to redefine method '#{method(method_name)}'" if methods.include?(method_name)

  define_method(method_name) do |*members, remove_duplicates: true, remove_order: true, alias_as: table_name|
    members = flatten_ar_array(members)

    operator_sql =
      if members.any?
        operator.new(members, remove_duplicates: remove_duplicates, remove_order: remove_order).to_sql
      else
        where("1=0").to_sql
      end

    from(Arel.sql("(#{operator_sql}) #{alias_as}"))
  end

  # Array#flatten with ActiveRecord::Relation items will load the ActiveRecord::Relation.
  # Therefore we need to roll our own flatten method.
  unless method_defined?(:flatten_ar_array) # rubocop:disable Style/GuardClause
    define_method :flatten_ar_array do |ary|
      arrays = ary.dup
      result = []

      until arrays.empty?
        item = arrays.shift
        if item.is_a?(Array)
          arrays.concat(item.dup)
        else
          result.push(item)
        end
      end

      result
    end
    private :flatten_ar_array
  end
end