Module: TreeNodes::ClassMethods

Defined in:
backend/app/model/mixins/tree_nodes.rb

Instance Method Summary collapse

Instance Method Details

#calculate_has_unpublished_ancestor(obj, check_root_record = true) ⇒ Object 



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# File 'backend/app/model/mixins/tree_nodes.rb', line 492

def calculate_has_unpublished_ancestor(obj, check_root_record = true)
  if check_root_record && obj.root_record_id
    root = root_model[obj.root_record_id]
    return true if root.publish == 0 || root.suppressed == 1
  end

  if obj.parent_id
    parent = node_model[obj.parent_id]
    if parent.publish == 0 || parent.suppressed == 1
      return true
    else
      return calculate_has_unpublished_ancestor(parent, false)
    end
  end

  false
end

#calculate_logical_ao_positions(objs) ⇒ Object 



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# File 'backend/app/model/mixins/tree_nodes.rb', line 444

def calculate_logical_ao_positions(objs)
  # For each AO in our set, we want to know how many have the same parent
  # but a smaller position.  Which is another way of saying "how many
  # records are before me in the list?"
  #
  # Previously we would do each as a query:
  #
  #   self.class.dataset.filter(:parent_name => self.parent_name).where { position < relative_position }.count
  #
  # but when you're dealing with trees containing hundreds of thousands of
  # records under a single node, this calculation gets slower (100+ ms) as
  # you get further down the list.
  #
  # We can speed things up for batches of records by ordering our records by
  # their DB position (say that gives us [A, B, C]), and then using the
  # following method:
  #
  #   * A's logical position is count(< A.position) -- as before
  #   * B's position is A.logical_position + count(< B.position && >= A.position)
  #   * C's position is B.logical_position + count(< C.position && >= B.position)
  #
  # Calculating the position for A incurs the same cost as before, but B
  # only needs to count the records between itself and A, and C only needs
  # to count the records between itself and B.  These ranges will be much
  # smaller in many cases.

  result = {}

  objs.group_by(&:parent_name).each do |parent_name, obj_group|
    next if parent_name.nil?

    sorted = obj_group.sort_by(&:position)

    last_physical_position = 0
    last_logical_position = 0

    sorted.each do |ao|
      c = self.dataset.filter(:parent_name => ao.parent_name).where { (position < ao.position) & (position >= last_physical_position) }.count

      last_logical_position = result[ao] = last_logical_position + c
      last_physical_position = ao.position
    end
  end

  result
end

#calculate_object_graph(object_graph, opts = {}) ⇒ Object 



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# File 'backend/app/model/mixins/tree_nodes.rb', line 511

def calculate_object_graph(object_graph, opts = {})
  object_graph.each do |model, id_list|
    next if self != model

    ids = self.any_repo.filter(:parent_id => id_list).
               select(:id).map {|row|
      row[:id]
    }

    object_graph.add_objects(self, ids)
  end

  super
end

#create_from_json(json, extra_values = {}) ⇒ Object 



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# File 'backend/app/model/mixins/tree_nodes.rb', line 337

def create_from_json(json, extra_values = {})
  obj = nil

  retry_db_update do
    DB.open do
      position_values = determine_tree_position_for_new_node(json)
      obj = super(json, extra_values.merge(position_values))
    end
  end

  if obj.nil?
    Log.error("Failed to set the position for #{node_model}: #{last_error}")
    raise last_error
  end

  migration = extra_values[:migration] ? extra_values[:migration].value : false
  if json.position && !migration
    obj.set_position_in_list(json.position)
  end

  ensure_consistent_tree(obj)

  obj
end

#determine_tree_position_for_new_node(json) ⇒ Object 



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# File 'backend/app/model/mixins/tree_nodes.rb', line 363

def determine_tree_position_for_new_node(json)
  result = {}

  root_record_uri = json[root_record_type]['ref']
  result["root_record_id"] = JSONModel.parse_reference(root_record_uri).fetch(:id)

  # 'parent_name' is a bit funny.  We need this column because the combination
  # of (parent, position) needs to be unique, to ensure that two siblings
  # don't occupy the same position when ordering them.  However, parent_id can
  # be NULL, meaning that the current node is at the top level of the tree.
  # This prevents the uniqueness check for working against top-level elements.
  #
  # So, parent_name gets used as a stand in in this case: it always has a
  # value for any node belonging to a hierarchy, and this value gets used in
  # the uniqueness check.
  #
  if json.parent
    parent_id = JSONModel.parse_reference(json.parent['ref']).fetch(:id)

    result["parent_id"] = parent_id
    result["parent_name"] = "#{parent_id}@#{self.node_record_type}"
  else
    result["parent_id"] = nil
    result["parent_name"] = "root@#{root_record_uri}"
  end

  # We'll add this new node to the end of the list.  To do that, find the
  # maximum position assigned so far and go TreeNodes::POSITION_STEP places
  # after that.  If another create_from_json gets in first, we'll have to
  # retry, but that's fine.
  result["position"] = next_position_for_parent(result['root_record_id'], result['parent_id'])

  result
end

#ensure_consistent_tree(obj) ⇒ Object 



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# File 'backend/app/model/mixins/tree_nodes.rb', line 326

def ensure_consistent_tree(obj)
  if obj.parent_id
    parent_root_record_id = node_model.filter(:id => obj.parent_id).get(:root_record_id)
    unless obj.root_record_id == parent_root_record_id
      raise "Consistency check failed: " \
            "#{node_model} #{obj.id} is in #{root_model} #{obj.root_record_id}," \
            " but its parent is in #{root_model} #{parent_root_record_id}."
    end
  end
end

#handle_delete(ids_to_delete) ⇒ Object 



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# File 'backend/app/model/mixins/tree_nodes.rb', line 527

def handle_delete(ids_to_delete)
  ids = self.filter(:id => ids_to_delete )

  # Update the root record's mtime so that any tree-related records are reindexed
  root_model.filter(:id => ids.select(:root_record_id)).update(:system_mtime => Time.now)

  # lets get a group of records that have unique parents or root_records
  parents = ids.select_group(:parent_id, :root_record_id).all
  # we then nil out the parent id so deletes can do its thing
  ids.update(:parent_id => nil)
  # trigger the deletes...
  super
end

#next_position_for_parent(root_record_id, parent_id) ⇒ Object 



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# File 'backend/app/model/mixins/tree_nodes.rb', line 398

def next_position_for_parent(root_record_id, parent_id)
  max_position = DB.open do |db|
    db[node_model.table_name]
      .filter(:root_record_id => root_record_id, :parent_id => parent_id)
      .select(:position)
      .max(:position)
  end
  max_position ||= 0

  max_position + TreeNodes::POSITION_STEP
end

#node_model ⇒ Object 



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# File 'backend/app/model/mixins/tree_nodes.rb', line 322

def node_model
  Kernel.const_get(node_record_type.camelize)
end

#node_record_type ⇒ Object 



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# File 'backend/app/model/mixins/tree_nodes.rb', line 312

def node_record_type
  @node_record_type
end

#ordered_record_properties(record_ids) ⇒ Object

Default: to be overriden by implementing models



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# File 'backend/app/model/mixins/tree_nodes.rb', line 542

def ordered_record_properties(record_ids)
  {}
end

#retry_db_update(&block) ⇒ Object 



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# File 'backend/app/model/mixins/tree_nodes.rb', line 285

def retry_db_update(&block)
  finished = false
  last_error = nil

  TreeNodes::DB_RETRIES.times do
    break if finished

    DB.attempt {
      block.call
      return
    }.and_if_constraint_fails {|err|
      last_error = err
    }
  end

  raise last_error
end

#root_model ⇒ Object 



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# File 'backend/app/model/mixins/tree_nodes.rb', line 317

def root_model
  Kernel.const_get(root_record_type.camelize)
end

#root_record_type ⇒ Object 



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# File 'backend/app/model/mixins/tree_nodes.rb', line 308

def root_record_type
  @root_record_type
end

#sequel_to_jsonmodel(objs, opts = {}) ⇒ Object 



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# File 'backend/app/model/mixins/tree_nodes.rb', line 410

def sequel_to_jsonmodel(objs, opts = {})
  jsons = super

  positions = calculate_logical_ao_positions(objs)

  jsons.zip(objs).each do |json, obj|
    if obj.root_record_id
      json[root_record_type] = {'ref' => uri_for(root_record_type, obj.root_record_id)}

      if obj.parent_id
        json.parent = {'ref' => uri_for(node_record_type, obj.parent_id)}
      end

      if obj.parent_name
        # Calculate the logical (gapless) position of this node.  This
        # bridges the gap between the DB's view of position, which only
        # cares that the positions order correctly, with the API's view,
        # which speaks in logical numbering (i.e. the first position is 0,
        # the second position is 1, etc.)

        json.position = positions.fetch(obj)
      end

    end

    if node_model.publishable?
      json['has_unpublished_ancestor'] = calculate_has_unpublished_ancestor(obj)
    end
  end

  jsons
end

#tree_record_types(root, node) ⇒ Object 



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# File 'backend/app/model/mixins/tree_nodes.rb', line 303

def tree_record_types(root, node)
  @root_record_type = root.to_s
  @node_record_type = node.to_s
end