Help:Remnant entities

Remnant entities (or ghosts) are assignments in tables without a corresponding entry in a the field of database table.

The  field for an entity contains the collective hash of those values that the tables (hereby annotations) currently suppose to have assignments for to provide an efficient diffing mechanism for the updater to decided which tables require an insert/delete without reading each single table and compare its values.

The occurrence of remnant entities should rarely happen but has been observed CiteRef::gh:smw:3849 and is most likely caused by an aborted update with an unsuccessful rollback which under some circumstances can create an imbalance in the record of the field.

CiteRef::gh:smw:3866 is provided to help remove entities classified as remnant by running additional table queries during an update. This may have a performance impact therefore see the configuration parameters documentation for further information.