Method: Factbase#txn

Defined in:

lib/factbase.rb

#txn ⇒ Factbase::Churn

Run an ACID transaction, which will either modify the factbase or rollback in case of an error.

If necessary to terminate a transaction and rollback all changes, you should raise the Factbase::Rollback exception:

fb = Factbase.new
fb.txn do |fbt|
  fbt.insert.bar = 42
  raise Factbase::Rollback
end

At the end of this script, the factbase will be empty. No facts will be inserted and all changes that happened in the block will be rolled back.

Returns:

• (Factbase::Churn) —

  How many facts have been changed (zero if rolled back)

# File 'lib/factbase.rb', line 167

def txn
  pairs = {}
  before =
    @maps.map do |m|
      n = m.transform_values(&:dup)
      # rubocop:disable Lint/HashCompareByIdentity
      pairs[n.object_id] = m.object_id
      # rubocop:enable Lint/HashCompareByIdentity
      n
    end
  require_relative 'factbase/taped'
  taped = Factbase::Taped.new(before)
  begin
    require_relative 'factbase/light'
    yield Factbase::Light.new(Factbase.new(taped))
  rescue Factbase::Rollback
    return 0
  end
  require_relative 'factbase/churn'
  churn = Factbase::Churn.new
  taped.inserted.each do |oid|
    b = taped.find_by_object_id(oid)
    next if b.nil?
    @maps << b
    churn.append(1, 0, 0)
  end
  garbage = []
  taped.added.each do |oid|
    b = taped.find_by_object_id(oid)
    next if b.nil?
    garbage << pairs[oid]
    @maps << b
    churn.append(0, 0, 1)
  end
  taped.deleted.each do |oid|
    garbage << pairs[oid]
    churn.append(0, 1, 0)
  end
  @maps.delete_if { |m| garbage.include?(m.object_id) }
  churn
end