The property _operatorStores is a dangerous optimisation to share the stores between the fields of the same type.
Indeed, store is data but also filtering and sorting...
we should replace these constants by a method _createStore(type)
sprieul : a quick search, only _logicalOperatorStore and _operatorStores are used. _andOperatorStore, _enumerationStores and _languagesEnumerationStore seems to be unused.