def includeme(config):
    tables = config.registry['metadata'].tables

    config.include('amnesia.modules.authentication.mapper')
    config.include('amnesia.modules.state.mapper')
    config.include('amnesia.modules.content_type.mapper')
    config.include('amnesia.modules.tag.mapper')

    _count_alias = tables['content'].alias('_count_children')

    orm.mapper(
        Content, tables['content'],
        polymorphic_on=tables['content'].c.content_type_id,
        properties={

            # no need to load this column by default
            'fts': orm.deferred(tables['content'].c.fts),

            #################
            # RELATIONSHIPS #
            #################

            'owner': orm.relationship(
                Account,
                lazy='joined',
                innerjoin=True,
                backref=orm.backref('contents', lazy='dynamic',
                                    cascade='all, delete-orphan')
            ),

            'state': orm.relationship(
                State,
                lazy='joined',
                innerjoin=True
            ),

            'type': orm.relationship(
                ContentType,
                lazy='joined',
                innerjoin=True
            ),

            'tags': orm.relationship(
                Tag,
                secondary=tables['content_tag']
            ),

            'parent': orm.relationship(
                Folder,
                foreign_keys=tables['content'].c.container_id,
                innerjoin=True,
                uselist=False,
                backref=orm.backref('children', cascade='all, delete-orphan')
            ),

            #####################
            # COLUMN PROPERTIES #
            #####################

            'position_in_container': orm.column_property(
                sql.func.row_number().
                over(partition_by=tables['content'].c.container_id,
                     order_by=tables['content'].c.weight.desc()),
                deferred=True,
                group='window_func'
            ),

            # FIXME: move to folder mapper with a LATERAL expression
            'count_children' : orm.column_property(
                sql.select([sql.func.count()]).where(
                    _count_alias.c.container_id == tables['content'].c.id
                ).correlate(tables['content']).label('count_children'),
                deferred = True
            ),

        })