mvcc/watcher_group.go
func (wg *watcherGroup) delete(wa *watcher) bool {
	if _, ok := wg.watchers[wa]; !ok {
		return false
	}
	wg.watchers.delete(wa)
	if wa.end == nil {
		wg.keyWatchers.delete(wa)
		return true
	}

	ivl := adt.NewStringAffineInterval(string(wa.key), string(wa.end))
	iv := wg.ranges.Find(ivl)
	if iv == nil {
		return false
	}

	ws := iv.Val.(watcherSet)
	delete(ws, wa)
	if len(ws) == 0 {
		// remove interval missing watchers
		if ok := wg.ranges.Delete(ivl); !ok {
			panic("could not remove watcher from interval tree")
		}
	}

	return true
}
func (wg *watcherGroup) delete(wa *watcher) bool {
	if _, ok := wg.watchers[wa]; !ok {
		return false
	}
	wg.watchers.delete(wa)
	if wa.end == nil {
		wg.keyWatchers.delete(wa)
		return true
	}

	ivl := adt.NewStringAffineInterval(string(wa.key), string(wa.end))
	iv := wg.ranges.Find(ivl)
	if iv == nil {
		return false
	}

	ws := iv.Val.(watcherSet)
	delete(ws, wa)
	if len(ws) == 0 {
		// remove interval missing watchers
		if ok := wg.ranges.Delete(ivl); !ok {
			panic("could not remove watcher from interval tree")
		}
	}

	return true
}
// delete removes a watcher from the group.