Error: Unauthorized assignment to lft: it's an internal field handled by acts_as_nested_set code, use move_to_* methods instead

[redminechick]

I am getting this error: "Unauthorized assignment to lft: it's an internal field handled by acts_as_nested_set code, use move_to_* methods instead." whilst running this code: rake redmine:merge_redmine RAILS_ENV=production (the aim to to merge 2 databases with different data and both databases have the same schema. ) via Bitnami Redmine Stacks version 2.2.1-0 in windows 7 platform and on windows server 2008 r2. I am very new to Ruby on Rails and do not know what the error means and how to fix it. Any pointers / guidance would be very much appreciated!

Thank you for you time!

[skyeagle]

First of all. The redmine uses custom vendored awesome nested set plugin and it is not related to this one. This error mean that you are trying to manipulate with field of db that is used only for internal needs of the plugin.

[redminechick]

Thank you skyeagle for your comment. What do I need to do or how to fix it? Any pointers is very much appreciated. :) Have a good day.

[skyeagle]

Take a look on your code, search for accessors like lft=, rgt=. Replace them with the self['lft'] = and self['rgt']= accordingly.

UPD: self['rgt']= will be properly

[redminechick]

I have followed your instructions and the above error is solved, however its given me a different error :( and it did stop 2 of my Redmine services. If you dont mind, please have a quick at this code I have (original code:)

module CollectiveIdea #:nodoc:
module Acts #:nodoc:
module NestedSet #:nodoc:

  # This acts provides Nested Set functionality. Nested Set is a smart way to implement
  # an _ordered_ tree, with the added feature that you can select the children and all of their
  # descendants with a single query. The drawback is that insertion or move need some complex
  # sql queries. But everything is done here by this module!
  #
  # Nested sets are appropriate each time you want either an orderd tree (menus,
  # commercial categories) or an efficient way of querying big trees (threaded posts).
  #
  # == API
  #
  # Methods names are aligned with acts_as_tree as much as possible to make replacment from one
  # by another easier.
  #
  #   item.children.create(:name => "child1")
  #

  # Configuration options are:
  #
  # * +:parent_column+ - specifies the column name to use for keeping the position integer (default: parent_id)
  # * +:left_column+ - column name for left boundry data, default "lft"
  # * +:right_column+ - column name for right boundry data, default "rgt"
  # * +:scope+ - restricts what is to be considered a list. Given a symbol, it'll attach "_id"
  #   (if it hasn't been already) and use that as the foreign key restriction. You
  #   can also pass an array to scope by multiple attributes.
  #   Example: <tt>acts_as_nested_set :scope => [:notable_id, :notable_type]</tt>
  # * +:dependent+ - behavior for cascading destroy. If set to :destroy, all the
  #   child objects are destroyed alongside this object by calling their destroy
  #   method. If set to :delete_all (default), all the child objects are deleted
  #   without calling their destroy method.
  # * +:counter_cache+ adds a counter cache for the number of children.
  #   defaults to false.
  #   Example: <tt>acts_as_nested_set :counter_cache => :children_count</tt>
  #
  # See CollectiveIdea::Acts::NestedSet::Model::ClassMethods for a list of class methods and
  # CollectiveIdea::Acts::NestedSet::Model for a list of instance methods added
  # to acts_as_nested_set models
  def acts_as_nested_set(options = {})
    options = {
      :parent_column => 'parent_id',
      :left_column => 'lft',
      :right_column => 'rgt',
      :dependent => :delete_all, # or :destroy
      :counter_cache => false,
      :order => 'id'
    }.merge(options)

    if options[:scope].is_a?(Symbol) && options[:scope].to_s !~ /_id$/
      options[:scope] = "#{options[:scope]}_id".intern
    end

    class_attribute :acts_as_nested_set_options
    self.acts_as_nested_set_options = options

    include CollectiveIdea::Acts::NestedSet::Model
    include Columns
    extend Columns

    belongs_to :parent, :class_name => self.base_class.to_s,
      :foreign_key => parent_column_name,
      :counter_cache => options[:counter_cache],
      :inverse_of => :children
    has_many :children, :class_name => self.base_class.to_s,
      :foreign_key => parent_column_name, :order => left_column_name,
      :inverse_of => :parent,
      :before_add    => options[:before_add],
      :after_add     => options[:after_add],
      :before_remove => options[:before_remove],
      :after_remove  => options[:after_remove]

    attr_accessor :skip_before_destroy

    before_create  :set_default_left_and_right
    before_save    :store_new_parent
    after_save     :move_to_new_parent
    before_destroy :destroy_descendants

    # no assignment to structure fields
    [left_column_name, right_column_name].each do |column|
      module_eval <<-"end_eval", __FILE__, __LINE__
        def #{column}=(x)
          raise ActiveRecord::ActiveRecordError, "Unauthorized assignment to #{column}: it's an internal field handled by acts_as_nested_set code, use move_to_* methods instead."
        end
      end_eval
    end

    define_model_callbacks :move
  end

  module Model
    extend ActiveSupport::Concern

    module ClassMethods
      # Returns the first root
      def root
        roots.first
      end

      def roots
        where(parent_column_name => nil).order(quoted_left_column_name)
      end

      def leaves
        where("#{quoted_right_column_name} - #{quoted_left_column_name} = 1").order(quoted_left_column_name)
      end

      def valid?
        left_and_rights_valid? && no_duplicates_for_columns? && all_roots_valid?
      end

      def left_and_rights_valid?
        joins("LEFT OUTER JOIN #{quoted_table_name} AS parent ON " +
            "#{quoted_table_name}.#{quoted_parent_column_name} = parent.#{primary_key}").
        where(
            "#{quoted_table_name}.#{quoted_left_column_name} IS NULL OR " +
            "#{quoted_table_name}.#{quoted_right_column_name} IS NULL OR " +
            "#{quoted_table_name}.#{quoted_left_column_name} >= " +
              "#{quoted_table_name}.#{quoted_right_column_name} OR " +
            "(#{quoted_table_name}.#{quoted_parent_column_name} IS NOT NULL AND " +
              "(#{quoted_table_name}.#{quoted_left_column_name} <= parent.#{quoted_left_column_name} OR " +
              "#{quoted_table_name}.#{quoted_right_column_name} >= parent.#{quoted_right_column_name}))"
        ).count == 0
      end

      def no_duplicates_for_columns?
        scope_string = Array(acts_as_nested_set_options[:scope]).map do |c|
          connection.quote_column_name(c)
        end.push(nil).join(", ")
        [quoted_left_column_name, quoted_right_column_name].all? do |column|
          # No duplicates
          select("#{scope_string}#{column}, COUNT(#{column})").
              group("#{scope_string}#{column}").
              having("COUNT(#{column}) > 1").
              first.nil?
        end
      end

      # Wrapper for each_root_valid? that can deal with scope.
      def all_roots_valid?
        if acts_as_nested_set_options[:scope]
          roots.group(scope_column_names).group_by{|record| scope_column_names.collect{|col| record.send(col.to_sym)}}.all? do |scope, grouped_roots|
            each_root_valid?(grouped_roots)
          end
        else
          each_root_valid?(roots)
        end
      end

      def each_root_valid?(roots_to_validate)
        left = right = 0
        roots_to_validate.all? do |root|
          (root.left > left && root.right > right).tap do
            left = root.left
            right = root.right
          end
        end
      end

      # Rebuilds the left & rights if unset or invalid.
      # Also very useful for converting from acts_as_tree.
      def rebuild!(validate_nodes = true)
        # Don't rebuild a valid tree.
        return true if valid?

        scope = lambda{|node|}
        if acts_as_nested_set_options[:scope]
          scope = lambda{|node|
            scope_column_names.inject(""){|str, column_name|
              str << "AND #{connection.quote_column_name(column_name)} = #{connection.quote(node.send(column_name.to_sym))} "
            }
          }
        end
        indices = {}

        set_left_and_rights = lambda do |node|
          # set left
          node[left_column_name] = indices[scope.call(node)] += 1
          # find
          where(["#{quoted_parent_column_name} = ? #{scope.call(node)}", node]).order(acts_as_nested_set_options[:order]).each{|n| set_left_and_rights.call(n) }
          # set right
          node[right_column_name] = indices[scope.call(node)] += 1
          node.save!(:validate => validate_nodes)
        end

        # Find root node(s)
        root_nodes = where("#{quoted_parent_column_name} IS NULL").order(acts_as_nested_set_options[:order]).each do |root_node|
          # setup index for this scope
          indices[scope.call(root_node)] ||= 0
          set_left_and_rights.call(root_node)
        end
      end

      # Iterates over tree elements and determines the current level in the tree.
      # Only accepts default ordering, odering by an other column than lft
      # does not work. This method is much more efficent than calling level
      # because it doesn't require any additional database queries.
      #
      # Example:
      #    Category.each_with_level(Category.root.self_and_descendants) do |o, level|
      #
      def each_with_level(objects)
        path = [nil]
        objects.each do |o|
          if o.parent_id != path.last
            # we are on a new level, did we decent or ascent?
            if path.include?(o.parent_id)
              # remove wrong wrong tailing paths elements
              path.pop while path.last != o.parent_id
            else
              path << o.parent_id
            end
          end
          yield(o, path.length - 1)
        end
      end
    end

    # Any instance method that returns a collection makes use of Rails 2.1's named_scope (which is bundled for Rails 2.0), so it can be treated as a finder.
    #
    #   category.self_and_descendants.count
    #   category.ancestors.find(:all, :conditions => "name like '%foo%'")

    # Value of the parent column
    def parent_id
      self[parent_column_name]
    end

    # Value of the left column
    def left
      self[left_column_name]
    end

    # Value of the right column
    def right
      self[right_column_name]
    end

    # Returns true if this is a root node.
    def root?
      parent_id.nil?
    end

    def leaf?
      new_record? || (right - left == 1)
    end

    # Returns true is this is a child node
    def child?
      !parent_id.nil?
    end

    # Returns root
    def root
      self_and_ancestors.where(parent_column_name => nil).first
    end

    # Returns the array of all parents and self
    def self_and_ancestors
      nested_set_scope.where([
        "#{self.class.quoted_table_name}.#{quoted_left_column_name} <= ? AND #{self.class.quoted_table_name}.#{quoted_right_column_name} >= ?", left, right
      ])
    end

    # Returns an array of all parents
    def ancestors
      without_self self_and_ancestors
    end

    # Returns the array of all children of the parent, including self
    def self_and_siblings
      nested_set_scope.where(parent_column_name => parent_id)
    end

    # Returns the array of all children of the parent, except self
    def siblings
      without_self self_and_siblings
    end

    # Returns a set of all of its nested children which do not have children
    def leaves
      descendants.where("#{self.class.quoted_table_name}.#{quoted_right_column_name} - #{self.class.quoted_table_name}.#{quoted_left_column_name} = 1")
    end

    # Returns the level of this object in the tree
    # root level is 0
    def level
      parent_id.nil? ? 0 : ancestors.count
    end

    # Returns a set of itself and all of its nested children
    def self_and_descendants
      nested_set_scope.where([
        "#{self.class.quoted_table_name}.#{quoted_left_column_name} >= ? AND #{self.class.quoted_table_name}.#{quoted_right_column_name} <= ?", left, right
      ])
    end

    # Returns a set of all of its children and nested children
    def descendants
      without_self self_and_descendants
    end

    def is_descendant_of?(other)
      other.left < self.left && self.left < other.right && same_scope?(other)
    end

    def is_or_is_descendant_of?(other)
      other.left <= self.left && self.left < other.right && same_scope?(other)
    end

    def is_ancestor_of?(other)
      self.left < other.left && other.left < self.right && same_scope?(other)
    end

    def is_or_is_ancestor_of?(other)
      self.left <= other.left && other.left < self.right && same_scope?(other)
    end

    # Check if other model is in the same scope
    def same_scope?(other)
      Array(acts_as_nested_set_options[:scope]).all? do |attr|
        self.send(attr) == other.send(attr)
      end
    end

    # Find the first sibling to the left
    def left_sibling
      siblings.where(["#{self.class.quoted_table_name}.#{quoted_left_column_name} < ?", left]).
              order("#{self.class.quoted_table_name}.#{quoted_left_column_name} DESC").last
    end

    # Find the first sibling to the right
    def right_sibling
      siblings.where(["#{self.class.quoted_table_name}.#{quoted_left_column_name} > ?", left]).first
    end

    # Shorthand method for finding the left sibling and moving to the left of it.
    def move_left
      move_to_left_of left_sibling
    end

    # Shorthand method for finding the right sibling and moving to the right of it.
    def move_right
      move_to_right_of right_sibling
    end

    # Move the node to the left of another node (you can pass id only)
    def move_to_left_of(node)
      move_to node, :left
    end

    # Move the node to the left of another node (you can pass id only)
    def move_to_right_of(node)
      move_to node, :right
    end

    # Move the node to the child of another node (you can pass id only)
    def move_to_child_of(node)
      move_to node, :child
    end

    # Move the node to root nodes
    def move_to_root
      move_to nil, :root
    end

    def move_possible?(target)
      self != target && # Can't target self
      same_scope?(target) && # can't be in different scopes
      # !(left..right).include?(target.left..target.right) # this needs tested more
      # detect impossible move
      !((left <= target.left && right >= target.left) or (left <= target.right && right >= target.right))
    end

    def to_text
      self_and_descendants.map do |node|
        "#{'*'*(node.level+1)} #{node.id} #{node.to_s} (#{node.parent_id}, #{node.left}, #{node.right})"
      end.join("\n")
    end

  protected

    def without_self(scope)
      scope.where(["#{self.class.quoted_table_name}.#{self.class.primary_key} != ?", self])
    end

    # All nested set queries should use this nested_set_scope, which performs finds on
    # the base ActiveRecord class, using the :scope declared in the acts_as_nested_set
    # declaration.
    def nested_set_scope(options = {})
      options = {:order => "#{self.class.quoted_table_name}.#{quoted_left_column_name}"}.merge(options)
      scopes = Array(acts_as_nested_set_options[:scope])
      options[:conditions] = scopes.inject({}) do |conditions,attr|
        conditions.merge attr => self[attr]
      end unless scopes.empty?
      self.class.base_class.scoped options
    end

    def store_new_parent
      @move_to_new_parent_id = send("#{parent_column_name}_changed?") ? parent_id : false
      true # force callback to return true
    end

    def move_to_new_parent
      if @move_to_new_parent_id.nil?
        move_to_root
      elsif @move_to_new_parent_id
        move_to_child_of(@move_to_new_parent_id)
      end
    end

    # on creation, set automatically lft and rgt to the end of the tree
    def set_default_left_and_right
      highest_right_row = nested_set_scope(:order => "#{quoted_right_column_name} desc").find(:first, :limit => 1,:lock => true )
      maxright = highest_right_row ? (highest_right_row[right_column_name] || 0) : 0
      # adds the new node to the right of all existing nodes
      self[left_column_name] = maxright + 1
      self[right_column_name] = maxright + 2
    end

    def in_tenacious_transaction(&block)
      retry_count = 0
      begin
        transaction(&block)
      rescue ActiveRecord::StatementInvalid => error
        raise unless connection.open_transactions.zero?
        raise unless error.message =~ /Deadlock found when trying to get lock|Lock wait timeout exceeded/
        raise unless retry_count < 10
        retry_count += 1
        logger.info "Deadlock detected on retry #{retry_count}, restarting transaction"
        sleep(rand(retry_count)*0.1) # Aloha protocol
        retry
      end
    end

    # Prunes a branch off of the tree, shifting all of the elements on the right
    # back to the left so the counts still work.
    def destroy_descendants
      return if right.nil? || left.nil? || skip_before_destroy

      in_tenacious_transaction do
        reload_nested_set
        # select the rows in the model that extend past the deletion point and apply a lock
        self.class.base_class.find(:all,
          :select => "id",
          :conditions => ["#{quoted_left_column_name} >= ?", left],
          :lock => true
        )

        if acts_as_nested_set_options[:dependent] == :destroy
          descendants.each do |model|
            model.skip_before_destroy = true
            model.destroy
          end
        else
          nested_set_scope.delete_all(
            ["#{quoted_left_column_name} > ? AND #{quoted_right_column_name} < ?",
              left, right]
          )
        end

        # update lefts and rights for remaining nodes
        diff = right - left + 1
        nested_set_scope.update_all(
          ["#{quoted_left_column_name} = (#{quoted_left_column_name} - ?)", diff],
          ["#{quoted_left_column_name} > ?", right]
        )
        nested_set_scope.update_all(
          ["#{quoted_right_column_name} = (#{quoted_right_column_name} - ?)", diff],
          ["#{quoted_right_column_name} > ?", right]
          )

reload
# Don't allow multiple calls to destroy to corrupt the set
self.skip_before_destroy = true
end
end

    # reload left, right, and parent
    def reload_nested_set
      reload(
        :select => "#{quoted_left_column_name}, #{quoted_right_column_name}, #{quoted_parent_column_name}",
        :lock => true
      )
    end

    def move_to(target, position)
      raise ActiveRecord::ActiveRecordError, "You cannot move a new node" if self.new_record?
      run_callbacks :move do
        in_tenacious_transaction do
          if target.is_a? self.class.base_class
            target.reload_nested_set
          elsif position != :root
            # load object if node is not an object
            target = nested_set_scope.find(target)
          end
          self.reload_nested_set

          unless position == :root || move_possible?(target)
            raise ActiveRecord::ActiveRecordError, "Impossible move, target node cannot be inside moved tree."
          end

          bound = case position
            when :child;  target[right_column_name]
            when :left;   target[left_column_name]
            when :right;  target[right_column_name] + 1
            when :root;   1
            else raise ActiveRecord::ActiveRecordError, "Position should be :child, :left, :right or :root ('#{position}' received)."
          end

          if bound > self[right_column_name]
            bound = bound - 1
            other_bound = self[right_column_name] + 1
          else
            other_bound = self[left_column_name] - 1
          end

          # there would be no change
          return if bound == self[right_column_name] || bound == self[left_column_name]

          # we have defined the boundaries of two non-overlapping intervals,
          # so sorting puts both the intervals and their boundaries in order
          a, b, c, d = [self[left_column_name], self[right_column_name], bound, other_bound].sort

          # select the rows in the model between a and d, and apply a lock
          self.class.base_class.select('id').lock(true).where(
            ["#{quoted_left_column_name} >= :a and #{quoted_right_column_name} <= :d", {:a => a, :d => d}]
          )

          new_parent = case position
            when :child;  target.id
            when :root;   nil
            else          target[parent_column_name]
          end

          self.nested_set_scope.update_all([
            "#{quoted_left_column_name} = CASE " +
              "WHEN #{quoted_left_column_name} BETWEEN :a AND :b " +
                "THEN #{quoted_left_column_name} + :d - :b " +
              "WHEN #{quoted_left_column_name} BETWEEN :c AND :d " +
                "THEN #{quoted_left_column_name} + :a - :c " +
              "ELSE #{quoted_left_column_name} END, " +
            "#{quoted_right_column_name} = CASE " +
              "WHEN #{quoted_right_column_name} BETWEEN :a AND :b " +
                "THEN #{quoted_right_column_name} + :d - :b " +
              "WHEN #{quoted_right_column_name} BETWEEN :c AND :d " +
                "THEN #{quoted_right_column_name} + :a - :c " +
              "ELSE #{quoted_right_column_name} END, " +
            "#{quoted_parent_column_name} = CASE " +
              "WHEN #{self.class.base_class.primary_key} = :id THEN :new_parent " +
              "ELSE #{quoted_parent_column_name} END",
            {:a => a, :b => b, :c => c, :d => d, :id => self.id, :new_parent => new_parent}
          ])
        end
        target.reload_nested_set if target
        self.reload_nested_set
      end
    end

  end

  # Mixed into both classes and instances to provide easy access to the column names
  module Columns
    def left_column_name
      acts_as_nested_set_options[:left_column]
    end

    def right_column_name
      acts_as_nested_set_options[:right_column]
    end

    def parent_column_name
      acts_as_nested_set_options[:parent_column]
    end

    def scope_column_names
      Array(acts_as_nested_set_options[:scope])
    end

    def quoted_left_column_name
      connection.quote_column_name(left_column_name)
    end

    def quoted_right_column_name
      connection.quote_column_name(right_column_name)
    end

    def quoted_parent_column_name
      connection.quote_column_name(parent_column_name)
    end

    def quoted_scope_column_names
      scope_column_names.collect {|column_name| connection.quote_column_name(column_name) }
    end
  end

end

end
end

I have edited:
module CollectiveIdea #:nodoc:
module Acts #:nodoc:
module NestedSet #:nodoc:

  # This acts provides Nested Set functionality. Nested Set is a smart way to implement
  # an _ordered_ tree, with the added feature that you can select the children and all of their
  # descendants with a single query. The drawback is that insertion or move need some complex
  # sql queries. But everything is done here by this module!
  #
  # Nested sets are appropriate each time you want either an orderd tree (menus,
  # commercial categories) or an efficient way of querying big trees (threaded posts).
  #
  # == API
  #
  # Methods names are aligned with acts_as_tree as much as possible to make replacment from one
  # by another easier.
  #
  #   item.children.create(:name => "child1")
  #

  # Configuration options are:
  #
  # * +:parent_column+ - specifies the column name to use for keeping the position integer (default: parent_id)
  # * +:left_column+ - column name for left boundry data, default "lft"
  # * +:right_column+ - column name for right boundry data, default "rgt"
  # * +:scope+ - restricts what is to be considered a list. Given a symbol, it'll attach "_id"
  #   (if it hasn't been already) and use that as the foreign key restriction. You
  #   can also pass an array to scope by multiple attributes.
  #   Example: <tt>acts_as_nested_set :scope => [:notable_id, :notable_type]</tt>
  # * +:dependent+ - behavior for cascading destroy. If set to :destroy, all the
  #   child objects are destroyed alongside this object by calling their destroy
  #   method. If set to :delete_all (default), all the child objects are deleted
  #   without calling their destroy method.
  # * +:counter_cache+ adds a counter cache for the number of children.
  #   defaults to false.
  #   Example: <tt>acts_as_nested_set :counter_cache => :children_count</tt>
  #
  # See CollectiveIdea::Acts::NestedSet::Model::ClassMethods for a list of class methods and
  # CollectiveIdea::Acts::NestedSet::Model for a list of instance methods added
  # to acts_as_nested_set models
  def acts_as_nested_set(options = {})
    options = {
      :parent_column => 'parent_id',
      :left_column => 'lft',
      :right_column => 'rgt',
      :dependent => :delete_all, # or :destroy
      :counter_cache => false,
      :order => 'id'
    }.merge(options)

    if options[:scope].is_a?(Symbol) && options[:scope].to_s !~ /_id$/
      options[:scope] = "#{options[:scope]}_id".intern
    end

    class_attribute :acts_as_nested_set_options
    self.acts_as_nested_set_options = options

    include CollectiveIdea::Acts::NestedSet::Model
    include Columns
    extend Columns

    belongs_to :parent, :class_name => self.base_class.to_s,
      :foreign_key => parent_column_name,
      :counter_cache => options[:counter_cache],
      :inverse_of => :children
    has_many :children, :class_name => self.base_class.to_s,
      :foreign_key => parent_column_name, :order => left_column_name,
      :inverse_of => :parent,
      :before_add    => options[:before_add],
      :after_add     => options[:after_add],
      :before_remove => options[:before_remove],
      :after_remove  => options[:after_remove]

    attr_accessor :skip_before_destroy

    before_create  :set_default_left_and_right
    before_save    :store_new_parent
    after_save     :move_to_new_parent
    before_destroy :destroy_descendants

    # no assignment to structure fields
    [left_column_name, right_column_name].each do |column|
      module_eval <<-"end_eval", __FILE__, __LINE__
        def #{column}=(x)
          raise ActiveRecord::ActiveRecordError, "Unauthorized assignment to #{column}: it's an internal field handled by acts_as_nested_set code, use move_to_* methods instead."
        end
      end_eval
    end

    define_model_callbacks :move
  end

  module Model
    extend ActiveSupport::Concern

    module ClassMethods
      # Returns the first root
      def root
        roots.first
      end

      def roots
        where(parent_column_name => nil).order(quoted_left_column_name)
      end

      def leaves
        where("#{quoted_right_column_name} - #{quoted_left_column_name} = 1").order(quoted_left_column_name)
      end

      def valid?
        left_and_rights_valid? && no_duplicates_for_columns? && all_roots_valid?
      end

      def left_and_rights_valid?
        joins("LEFT OUTER JOIN #{quoted_table_name} AS parent ON " +
            "#{quoted_table_name}.#{quoted_parent_column_name} = parent.#{primary_key}").
        where(
            "#{quoted_table_name}.#{quoted_left_column_name} IS NULL OR " +
            "#{quoted_table_name}.#{quoted_right_column_name} IS NULL OR " +
            "#{quoted_table_name}.#{quoted_left_column_name} >= " +
              "#{quoted_table_name}.#{quoted_right_column_name} OR " +
            "(#{quoted_table_name}.#{quoted_parent_column_name} IS NOT NULL AND " +
              "(#{quoted_table_name}.#{quoted_left_column_name} <= parent.#{quoted_left_column_name} OR " +
              "#{quoted_table_name}.#{quoted_right_column_name} >= parent.#{quoted_right_column_name}))"
        ).count == 0
      end

      def no_duplicates_for_columns?
        scope_string = Array(acts_as_nested_set_options[:scope]).map do |c|
          connection.quote_column_name(c)
        end.push(nil).join(", ")
        [quoted_left_column_name, quoted_right_column_name].all? do |column|
          # No duplicates
          select("#{scope_string}#{column}, COUNT(#{column})").
              group("#{scope_string}#{column}").
              having("COUNT(#{column}) > 1").
              first.nil?
        end
      end

      # Wrapper for each_root_valid? that can deal with scope.
      def all_roots_valid?
        if acts_as_nested_set_options[:scope]
          roots.group(scope_column_names).group_by{|record| scope_column_names.collect{|col| record.send(col.to_sym)}}.all? do |scope, grouped_roots|
            each_root_valid?(grouped_roots)
          end
        else
          each_root_valid?(roots)
        end
      end

      def each_root_valid?(roots_to_validate)
        left = right = 0
        roots_to_validate.all? do |root|
          (root.left > left && root.right > right).tap do
            left = root.left
            right = root.right
          end
        end
      end

      # Rebuilds the left & rights if unset or invalid.
      # Also very useful for converting from acts_as_tree.
      def rebuild!(validate_nodes = true)
        # Don't rebuild a valid tree.
        return true if valid?

        scope = lambda{|node|}
        if acts_as_nested_set_options[:scope]
          scope = lambda{|node|
            scope_column_names.inject(""){|str, column_name|
              str << "AND #{connection.quote_column_name(column_name)} = #{connection.quote(node.send(column_name.to_sym))} "
            }
          }
        end
        indices = {}

        set_left_and_rights = lambda do |node|
          # set left
          node[left_column_name] = indices[scope.call(node)] += 1
          # find
          where(["#{quoted_parent_column_name} = ? #{scope.call(node)}", node]).order(acts_as_nested_set_options[:order]).each{|n| set_left_and_rights.call(n) }
          # set right
          node[right_column_name] = indices[scope.call(node)] += 1
          node.save!(:validate => validate_nodes)
        end

        # Find root node(s)
        root_nodes = where("#{quoted_parent_column_name} IS NULL").order(acts_as_nested_set_options[:order]).each do |root_node|
          # setup index for this scope
          indices[scope.call(root_node)] ||= 0
          set_left_and_rights.call(root_node)
        end
      end

      # Iterates over tree elements and determines the current level in the tree.
      # Only accepts default ordering, odering by an other column than lft
      # does not work. This method is much more efficent than calling level
      # because it doesn't require any additional database queries.
      #
      # Example:
      #    Category.each_with_level(Category.root.self_and_descendants) do |o, level|
      #
      def each_with_level(objects)
        path = [nil]
        objects.each do |o|
          if o.parent_id != path.last
            # we are on a new level, did we decent or ascent?
            if path.include?(o.parent_id)
              # remove wrong wrong tailing paths elements
              path.pop while path.last != o.parent_id
            else
              path << o.parent_id
            end
          end
          yield(o, path.length - 1)
        end
      end
    end

    # Any instance method that returns a collection makes use of Rails 2.1's named_scope (which is bundled for Rails 2.0), so it can be treated as a finder.
    #
    #   category.self_and_descendants.count
    #   category.ancestors.find(:all, :conditions => "name like '%foo%'")

    # Value of the parent column
    def parent_id
      self[parent_column_name]
    end

    # Value of the left column
    def left
      self[left_column_name]
    end

    # Value of the right column
    def right
      self[right_column_name]
    end

    # Returns true if this is a root node.
    def root?
      parent_id.nil?
    end

    def leaf?
      new_record? || (right - left == 1)
    end

    # Returns true is this is a child node
    def child?
      !parent_id.nil?
    end

    # Returns root
    def root
      self_and_ancestors.where(parent_column_name => nil).first
    end

    # Returns the array of all parents and self
    def self_and_ancestors
      nested_set_scope.where([
        "#{self.class.quoted_table_name}.#{quoted_left_column_name} <= ? AND #{self.class.quoted_table_name}.#{quoted_right_column_name} >= ?", left, right
      ])
    end

    # Returns an array of all parents
    def ancestors
      without_self self_and_ancestors
    end

    # Returns the array of all children of the parent, including self
    def self_and_siblings
      nested_set_scope.where(parent_column_name => parent_id)
    end

    # Returns the array of all children of the parent, except self
    def siblings
      without_self self_and_siblings
    end

    # Returns a set of all of its nested children which do not have children
    def leaves
      descendants.where("#{self.class.quoted_table_name}.#{quoted_right_column_name} - #{self.class.quoted_table_name}.#{quoted_left_column_name} = 1")
    end

    # Returns the level of this object in the tree
    # root level is 0
    def level
      parent_id.nil? ? 0 : ancestors.count
    end

    # Returns a set of itself and all of its nested children
    def self_and_descendants
      nested_set_scope.where([
        "#{self.class.quoted_table_name}.#{quoted_left_column_name} >= ? AND #{self.class.quoted_table_name}.#{quoted_right_column_name} <= ?", left, right
      ])
    end

    # Returns a set of all of its children and nested children
    def descendants
      without_self self_and_descendants
    end

    def is_descendant_of?(other)
      other.left < self.left && self.left < other.right && same_scope?(other)
    end

    def is_or_is_descendant_of?(other)
      other.left <= self.left && self.left < other.right && same_scope?(other)
    end

    def is_ancestor_of?(other)
      self.left < other.left && other.left < self.right && same_scope?(other)
    end

    def is_or_is_ancestor_of?(other)
      self.left <= other.left && other.left < self.right && same_scope?(other)
    end

    # Check if other model is in the same scope
    def same_scope?(other)
      Array(acts_as_nested_set_options[:scope]).all? do |attr|
        self.send(attr) == other.send(attr)
      end
    end

    # Find the first sibling to the left
    def left_sibling
      siblings.where(["#{self.class.quoted_table_name}.#{quoted_left_column_name} < ?", left]).
              order("#{self.class.quoted_table_name}.#{quoted_left_column_name} DESC").last
    end

    # Find the first sibling to the right
    def right_sibling
      siblings.where(["#{self.class.quoted_table_name}.#{quoted_left_column_name} > ?", left]).first
    end

    # Shorthand method for finding the left sibling and moving to the left of it.
    def move_left
      move_to_left_of left_sibling
    end

    # Shorthand method for finding the right sibling and moving to the right of it.
    def move_right
      move_to_right_of right_sibling
    end

    # Move the node to the left of another node (you can pass id only)
    def move_to_left_of(node)
      move_to node, :left
    end

    # Move the node to the left of another node (you can pass id only)
    def move_to_right_of(node)
      move_to node, :right
    end

    # Move the node to the child of another node (you can pass id only)
    def move_to_child_of(node)
      move_to node, :child
    end

    # Move the node to root nodes
    def move_to_root
      move_to nil, :root
    end

    def move_possible?(target)
      self != target && # Can't target self
      same_scope?(target) && # can't be in different scopes
      # !(left..right).include?(target.left..target.right) # this needs tested more
      # detect impossible move
      !((left <= target.left && right >= target.left) or (left <= target.right && right >= target.right))
    end

    def to_text
      self_and_descendants.map do |node|
        "#{'*'*(node.level+1)} #{node.id} #{node.to_s} (#{node.parent_id}, #{node.left}, #{node.right})"
      end.join("\n")
    end

  protected

    def without_self(scope)
      scope.where(["#{self.class.quoted_table_name}.#{self.class.primary_key} != ?", self])
    end

    # All nested set queries should use this nested_set_scope, which performs finds on
    # the base ActiveRecord class, using the :scope declared in the acts_as_nested_set
    # declaration.
    def nested_set_scope(options = {})
      options = {:order => "#{self.class.quoted_table_name}.#{quoted_left_column_name}"}.merge(options)
      scopes = Array(acts_as_nested_set_options[:scope])
      options[:conditions] = scopes.inject({}) do |conditions,attr|
        conditions.merge attr => self[attr]
      end unless scopes.empty?
      self.class.base_class.scoped options
    end

    def store_new_parent
      @move_to_new_parent_id = send("#{parent_column_name}_changed?") ? parent_id : false
      true # force callback to return true
    end

    def move_to_new_parent
      if @move_to_new_parent_id.nil?
        move_to_root
      elsif @move_to_new_parent_id
        move_to_child_of(@move_to_new_parent_id)
      end
    end

    # on creation, set automatically lft and rgt to the end of the tree
    def set_default_left_and_right
      highest_right_row = nested_set_scope(:order => "#{quoted_right_column_name} desc").find(:first, :limit => 1,:lock => true )
      maxright = highest_right_row ? (highest_right_row[right_column_name] || 0) : 0
      # adds the new node to the right of all existing nodes
      self[left_column_name] = maxright + 1
      self[right_column_name] = maxright + 2
    end

    def in_tenacious_transaction(&block)
      retry_count = 0
      begin
        transaction(&block)
      rescue ActiveRecord::StatementInvalid => error
        raise unless connection.open_transactions.zero?
        raise unless error.message =~ /Deadlock found when trying to get lock|Lock wait timeout exceeded/
        raise unless retry_count < 10
        retry_count += 1
        logger.info "Deadlock detected on retry #{retry_count}, restarting transaction"
        sleep(rand(retry_count)*0.1) # Aloha protocol
        retry
      end
    end

    # Prunes a branch off of the tree, shifting all of the elements on the right
    # back to the left so the counts still work.
    def destroy_descendants
      return if right.nil? || left.nil? || skip_before_destroy

      in_tenacious_transaction do
        reload_nested_set
        # select the rows in the model that extend past the deletion point and apply a lock
        self.class.base_class.find(:all,
          :select => "id",
          :conditions => ["#{quoted_left_column_name} >= ?", left],
          :lock => true
        )

        if acts_as_nested_set_options[:dependent] == :destroy
          descendants.each do |model|
            model.skip_before_destroy = true
            model.destroy
          end
        else
          nested_set_scope.delete_all(
            ["#{quoted_left_column_name} > ? AND #{quoted_right_column_name} < ?",
              left, right]
          )
        end

        # update lefts and rights for remaining nodes
        diff = right - left + 1
        nested_set_scope.update_all(
          ["#{quoted_left_column_name} = (#{quoted_left_column_name} - ?)", diff],
          ["#{quoted_left_column_name} > ?", right]
        )
        nested_set_scope.update_all(
          ["#{quoted_right_column_name} = (#{quoted_right_column_name} - ?)", diff],
          ["#{quoted_right_column_name} > ?", right]
          )

reload
# Don't allow multiple calls to destroy to corrupt the set
self.skip_before_destroy = true
end
end

    # reload left, right, and parent
    def reload_nested_set
      reload(
        :select => "#{quoted_left_column_name}, #{quoted_right_column_name}, #{quoted_parent_column_name}",
        :lock => true
      )
    end

    def move_to(target, position)
      raise ActiveRecord::ActiveRecordError, "You cannot move a new node" if self.new_record?
      run_callbacks :move do
        in_tenacious_transaction do
          if target.is_a? self.class.base_class
            target.reload_nested_set
          elsif position != :root
            # load object if node is not an object
            target = nested_set_scope.find(target)
          end
          self.reload_nested_set

          unless position == :root || move_possible?(target)
            raise ActiveRecord::ActiveRecordError, "Impossible move, target node cannot be inside moved tree."
          end

          bound = case position
            when :child;  target[right_column_name]
            when :left;   target[left_column_name]
            when :right;  target[right_column_name] + 1
            when :root;   1
            else raise ActiveRecord::ActiveRecordError, "Position should be :child, :left, :right or :root ('#{position}' received)."
          end

          if bound > self[right_column_name]
            bound = bound - 1
            other_bound = self[right_column_name] + 1
          else
            other_bound = self[left_column_name] - 1
          end

          # there would be no change
          return if bound == self[right_column_name] || bound == self[left_column_name]

          # we have defined the boundaries of two non-overlapping intervals,
          # so sorting puts both the intervals and their boundaries in order
          a, b, c, d = [self[left_column_name], self[right_column_name], bound, other_bound].sort

          # select the rows in the model between a and d, and apply a lock
          self.class.base_class.select('id').lock(true).where(
            ["#{quoted_left_column_name} >= :a and #{quoted_right_column_name} <= :d", {:a => a, :d => d}]
          )

          new_parent = case position
            when :child;  target.id
            when :root;   nil
            else          target[parent_column_name]
          end

          self.nested_set_scope.update_all([
            "#{quoted_left_column_name} = CASE " +
              "WHEN #{quoted_left_column_name} BETWEEN :a AND :b " +
                "THEN #{quoted_left_column_name} + :d - :b " +
              "WHEN #{quoted_left_column_name} BETWEEN :c AND :d " +
                "THEN #{quoted_left_column_name} + :a - :c " +
              "ELSE #{quoted_left_column_name} END, " +
            "#{quoted_right_column_name} = CASE " +
              "WHEN #{quoted_right_column_name} BETWEEN :a AND :b " +
                "THEN #{quoted_right_column_name} + :d - :b " +
              "WHEN #{quoted_right_column_name} BETWEEN :c AND :d " +
                "THEN #{quoted_right_column_name} + :a - :c " +
              "ELSE #{quoted_right_column_name} END, " +
            "#{quoted_parent_column_name} = CASE " +
              "WHEN #{self.class.base_class.primary_key} = :id THEN :new_parent " +
              "ELSE #{quoted_parent_column_name} END",
            {:a => a, :b => b, :c => c, :d => d, :id => self.id, :new_parent => new_parent}
          ])
        end
        target.reload_nested_set if target
        self.reload_nested_set
      end
    end

  end

  # Mixed into both classes and instances to provide easy access to the column names
  module Columns
    def left_column_name
      acts_as_nested_set_options[:left_column]
    end

    def right_column_name
      acts_as_nested_set_options[:right_column]
    end

    def parent_column_name
      acts_as_nested_set_options[:parent_column]
    end

    def scope_column_names
      Array(acts_as_nested_set_options[:scope])
    end

    def quoted_left_column_name
      connection.quote_column_name(left_column_name)
    end

    def quoted_right_column_name
      connection.quote_column_name(right_column_name)
    end

    def quoted_parent_column_name
      connection.quote_column_name(parent_column_name)
    end

    def quoted_scope_column_names
      scope_column_names.collect {|column_name| connection.quote_column_name(column_name) }
    end
  end

end

end
end

i have edited line 44, 45, 419 and 420 with your instructions, have I got this right?

the above screen dump is the new error complaining about [] is missing. Could you please give me more pointers? Thank you very much for your time, very much appreciated.

[skyeagle]

You are doing something wrong. When I said your code I meant your rake task that are doing merge but not the plugin functionality. It would be very dangerous to do modifications without understanding what are you doing. I will recommend you to contact with somebody who has real experience in programming.

[redminechick]

Thank you skyeagle for the comment. I have tried contacting everyone on internet to help me and no luck. Was given some links and it helped me to get to this last stage which is the only problem I have. Do you know anyone who can help me? Or can you offer me more guidance?

Thank you so much for replying.

[skyeagle]

I'm really sorry but your problem is more complicated and needs in direct participation of professional.

[redminechick]

Ok thank you.