diff --git a/db/migrate/20130917131710_planning_element_data_to_work_packages.rb b/db/migrate/20130917131710_planning_element_data_to_work_packages.rb
new file mode 100644
index 000000000000..bdf131a7e7be
--- /dev/null
+++ b/db/migrate/20130917131710_planning_element_data_to_work_packages.rb
@@ -0,0 +1,338 @@
+#-- copyright
+# OpenProject is a project management system.
+#
+# Copyright (C) 2012-2013 the OpenProject Team
+#
+# This program is free software; you can redistribute it and/or
+# modify it under the terms of the GNU General Public License version 3.
+#
+# See doc/COPYRIGHT.rdoc for more details.
+#++
+#
+class PlanningElementDataToWorkPackages < ActiveRecord::Migration
+  def up
+    add_new_id_column
+
+    return if skip_on_no_planning_elements
+
+    say_with_time "Inserting planning elements into the work packages table" do
+      add_planning_elements_to_work_packages
+    end
+
+    say_with_time "Rebuilding the nested set attributes on the newly inserted work packages" do
+      rebuild_nested_set
+    end
+  end
+
+  def down
+    say_with_time "Removing work packages that where planning elements" do
+      remove_planning_elements_from_work_packages
+    end
+
+    remove_new_id_column
+  end
+
+  private
+
+  def add_new_id_column
+    add_column :legacy_planning_elements, :new_id, :integer
+  end
+
+  def remove_new_id_column
+    remove_column :legacy_planning_elements, :new_id
+  end
+
+  # Appends the planning elements stored in
+  # legacy_planning_elements to the work_packages table.
+  #
+  # Some values are reconstructed from other tables and some are set
+  # with default values.
+  def add_planning_elements_to_work_packages
+    default_status_id = get_default_status_id
+    default_priority_id = get_default_priority_id
+
+    with_temporary_legacy_id_column do
+
+      insert_legacy_planning_elements_entries_to_work_packages(default_status_id, default_priority_id)
+
+      update_legacy_planning_elements_with_new_id
+    end
+  end
+
+  # Sets the nested set attributes parent_id, root_id, lft and rgt value
+  # to their now correct values.
+  def rebuild_nested_set
+    update_parent_id
+
+    set_root_id
+
+    set_lft_and_rgt
+  end
+
+  def get_default_status_id
+    default_status = select_one <<-SQL
+      SELECT id
+      FROM #{db_statuses_table}
+      WHERE position = 1
+      LIMIT 1
+    SQL
+
+    default_status['id']
+  end
+
+  def get_default_priority_id
+    default_priority = select_one <<-SQL
+      SELECT id
+      FROM #{db_enumerations_table}
+      WHERE #{db_column('is_default')} = #{quoted_true}
+      AND #{db_column('type')} = #{quote('IssuePriority')}
+      LIMIT 1
+    SQL
+
+    default_priority['id']
+  end
+
+  # Apends all entries from the legacy_planning_elements table to
+  # the work_packages table.
+  #
+  # Take most of the values from legacy_planning_elements.
+  # But take:
+  # * what was provided for status_id and priority_id
+  # * the type_id value from the legacy_planning_element_types table that got
+  #   an updated id by 20130916123916_planning_element_types_data_to_types.rb
+  # * the author_id from the user_id column of the first journal
+  #   (legacy_journals)
+  # * the lock_version from the maximum value of the version column of all
+  #   a planning_element's journals
+  #
+  # In case a legacy planning element did not have a planning_element_type_id
+  # the new type_id will be 0. This will have to be fixed. The plan is to do this
+  # via seed. Look there and you will find the fix if this comment is still up to date.
+  #
+  # This method will create a false parent_id. The parent_id column is
+  # still set to the id, the now work package has in the legacy_planning_elements
+  # table.
+  def insert_legacy_planning_elements_entries_to_work_packages(default_status_id, default_priority_id)
+
+
+    insert <<-SQL
+      INSERT INTO #{db_work_packages_table}
+        (
+          subject,
+          description,
+          project_id,
+          type_id,
+          start_date,
+          due_date,
+          status_id,
+          priority_id,
+          author_id,
+          created_at,
+          updated_at,
+          deleted_at,
+          parent_id,
+          lock_version,
+          legacy_planning_element_id
+        )
+      SELECT
+        #{db_planning_elements_table}.#{db_column('name')},
+        #{db_planning_elements_table}.#{db_column('description')},
+        #{db_planning_elements_table}.#{db_column('project_id')},
+        COALESCE(#{db_planning_element_types_table}.#{db_column('new_id')}, 0),
+        #{db_planning_elements_table}.#{db_column('start_date')},
+        #{db_planning_elements_table}.#{db_column('end_date')},
+        #{default_status_id} AS status_id,
+        #{default_priority_id} AS priority_id,
+        #{db_journals_table}.#{db_column('user_id')} AS author_id,
+        #{db_planning_elements_table}.#{db_column('created_at')},
+        #{db_planning_elements_table}.#{db_column('updated_at')},
+        #{db_planning_elements_table}.#{db_column('deleted_at')},
+        #{db_planning_elements_table}.#{db_column('parent_id')},
+        MAX(version_journals.#{db_column('version')}) AS lock_version,
+        #{db_planning_elements_table}.#{db_column('id')}
+      FROM #{db_planning_elements_table}
+      LEFT JOIN #{db_planning_element_types_table}
+        ON #{db_planning_elements_table}.#{db_column('planning_element_type_id')} = #{db_planning_element_types_table}.#{db_column('id')}
+      LEFT JOIN #{db_journals_table}
+        ON #{db_journals_table}.#{db_column('journaled_id')} = #{db_planning_elements_table}.#{db_column('id')}
+        AND #{db_journals_table}.#{db_column('version')} = 1
+        AND #{db_journals_table}.#{db_column('type')} = #{quote('Timelines_PlanningElementJournal')}
+      LEFT JOIN #{db_journals_table} AS version_journals
+        ON version_journals.#{db_column('journaled_id')} = #{db_planning_elements_table}.#{db_column('id')}
+        AND version_journals.#{db_column('type')} = #{quote('Timelines_PlanningElementJournal')}
+      GROUP BY
+        #{db_journals_table}.#{db_column('version')},
+        #{db_planning_elements_table}.#{db_column('name')},
+        #{db_planning_elements_table}.#{db_column('description')},
+        #{db_planning_elements_table}.#{db_column('project_id')},
+        #{db_planning_element_types_table}.#{db_column('new_id')},
+        #{db_planning_elements_table}.#{db_column('start_date')},
+        #{db_planning_elements_table}.#{db_column('end_date')},
+        #{db_journals_table}.#{db_column('user_id')},
+        #{db_planning_elements_table}.#{db_column('created_at')},
+        #{db_planning_elements_table}.#{db_column('updated_at')},
+        #{db_planning_elements_table}.#{db_column('deleted_at')},
+        #{db_planning_elements_table}.#{db_column('parent_id')},
+        #{db_planning_elements_table}.#{db_column('id')}
+    SQL
+  end
+
+  # Adds a column to the work packages table and removes it
+  # once the block is executed.
+  def with_temporary_legacy_id_column
+    add_column :work_packages, :legacy_planning_element_id, :integer
+
+    yield
+
+    remove_column :work_packages, :legacy_planning_element_id
+  end
+
+  def update_legacy_planning_elements_with_new_id
+     update <<-SQL
+      UPDATE #{db_planning_elements_table}
+      SET new_id = (SELECT #{db_work_packages_table}.#{db_column('id')}
+                    FROM #{db_work_packages_table}
+                    WHERE #{db_work_packages_table}.#{db_column('legacy_planning_element_id')} = #{db_planning_elements_table}.#{db_column('id')})
+    SQL
+  end
+
+  # Set the parent_id column of every work package that used to be a
+  # planning element (has a corresponding entry in the legacy_planning_elements
+  # table) to the new id of the parent work package.
+  def update_parent_id
+    update <<-SQL
+      UPDATE #{db_work_packages_table}
+      SET parent_id = (SELECT #{db_planning_elements_table}.#{db_column('new_id')}
+                       FROM #{db_planning_elements_table}
+                       WHERE #{db_planning_elements_table}.#{db_column('id')} = #{db_work_packages_table}.#{db_column('parent_id')})
+      WHERE EXISTS (SELECT *
+                    FROM #{db_planning_elements_table}
+                    WHERE #{db_work_packages_table}.#{db_column('id')} = #{db_planning_elements_table}.#{db_column('new_id')})
+    SQL
+  end
+
+  def set_root_id
+    set_root_id_for_non_children
+
+    set_root_id_for_children
+  end
+
+  # Set the root_id column of every work package that used to be a planning
+  # element (has a corresponding entry in the legacy_planning_elements
+  # table) and that does not have a parent_id to it's id column value.
+  def set_root_id_for_non_children
+    update <<-SQL
+      UPDATE #{db_work_packages_table}
+      SET #{db_column('root_id')} = #{db_work_packages_table}.#{db_column('id')}
+      WHERE EXISTS (SELECT *
+                    FROM #{db_planning_elements_table}
+                    WHERE #{db_work_packages_table}.#{db_column('id')} = #{db_planning_elements_table}.#{db_column('new_id')})
+      AND #{db_work_packages_table}.#{db_column('parent_id')} IS NULL
+    SQL
+  end
+
+  # Set the root_id column of every work package that used to be a planning
+  # element (has a corresponding entry in the legacy_planning_elements
+  # table) and that does have a parent_id to the new id of the former planning element
+  # that is the last element in the work package's ancestor chain.
+  #
+  # The approach here is top-down. Each entry who's root_id is NULL receives
+  # the root_id of it's parent's root_id.
+  # If the parent's root_id is set (e.g. 3029), this value is set to be the entry's
+  # root_id.
+  # If the parent's root_id is not set (i.e. NULL), this value is also set to be the
+  # entry's root_id. This does no harm.
+  # This is than repeated until no more entries without a root_id exist, i.e. are updated.
+  #
+  # Expects the root_id column of every work package that does not
+  # need to be addressed to be set, e.g. by using
+  # set_root_id_for_children
+  def set_root_id_for_children
+    num_updated = 1
+
+    while num_updated != 0
+      num_updated = update <<-SQL
+        UPDATE #{db_work_packages_table}
+        SET #{db_column('root_id')} = (SELECT parent.#{db_column('root_id')}
+                                       FROM #{db_work_packages_table} AS parent
+                                       WHERE parent.#{db_column('id')} = #{db_work_packages_table}.#{db_column('parent_id')})
+        WHERE #{db_work_packages_table}.#{db_column('root_id')} IS NULL
+      SQL
+    end
+  end
+
+  # Sets the lft and rgt columns of the newly added work packages
+  #
+  # This employs a method of WorkPackage, i.e. of a patch applied to
+  # awesome_nested_set which is included by WorkPackage.
+  #
+  # The alternative would be to copy over the code.
+  def set_lft_and_rgt
+    WorkPackage.selectively_rebuild_silently!
+  end
+
+  # Removes all work packages that where planning elements (have a
+  # corresponding entry in the legacy_planning_elements table)
+  def remove_planning_elements_from_work_packages
+    delete <<-SQL
+      DELETE FROM #{db_work_packages_table}
+      WHERE
+        id IN (SELECT #{db_column('new_id')}
+               FROM #{db_planning_elements_table})
+    SQL
+  end
+
+  def skip_on_no_planning_elements
+    planning_element = suppress_messages do
+      select_one <<-SQL
+        SELECT #{db_column('id')}
+        FROM #{db_planning_elements_table}
+        LIMIT 1
+      SQL
+    end
+
+    if planning_element.present?
+      false
+    else
+      say "There are no legacy planning elements to migrate... skipping."
+
+      true
+    end
+  end
+
+  def db_statuses_table
+    @db_statuses_table ||= quote_table_name('issue_statuses')
+  end
+
+  def db_enumerations_table
+    @db_enumerations_table ||= quote_table_name('enumerations')
+  end
+
+  def db_work_packages_table
+    @db_work_packages_table ||= quote_table_name('work_packages')
+  end
+
+  def db_planning_elements_table
+    @db_planning_elements_table ||= quote_table_name('legacy_planning_elements')
+  end
+
+  def db_planning_element_types_table
+    @db_planning_element_types_table ||= quote_table_name('legacy_planning_element_types')
+  end
+
+  def db_journals_table
+    @db_journals_table ||= quote_table_name('legacy_journals')
+  end
+
+  def db_column(name)
+    quote_column_name(name)
+  end
+
+  def say_with_time message
+    super do
+      suppress_messages do
+        yield
+      end
+    end
+  end
+end
diff --git a/doc/CHANGELOG.md b/doc/CHANGELOG.md
index a9f015f0ba67..06fd9b5c0f4d 100644
--- a/doc/CHANGELOG.md
+++ b/doc/CHANGELOG.md
@@ -31,6 +31,7 @@ See doc/COPYRIGHT.rdoc for more details.
 
 * `#1913` [Timelines] Enable drag&drop for select2 items in order to rearrange the order of the columns
 * `#1978` Migrate legacy issues
+* `#1979` Migrate legacy planning elements
 * `#1982` Migrate planning element types
 * `#1983` Migrate queries
 * `#1987` Migrate user rights