private void adjustIfBackingChanged() {
                if (owner.getItemCount()==initialOwnerLength) return;
                startIndex=owner.getItemIndex(startItem);
            }
Detects and attemts to compensate for a changed backing. Stop-gap measure until we get a through
design for this
container-search/src/main/java/com/yahoo/prelude/querytransform/PhraseMatcher.java