String parentId = Utils.getParentIdFromLowerLimit(fromKey);
TreeLock lock = acquireExclusive(parentId != null ? parentId : "");
long start = start();
try {
DBCursor cursor = dbCollection.find(query).sort(BY_ID_ASC).hint(hint);
ReadPreference readPreference =
getMongoReadPreference(collection, parentId, getDefaultReadPreference(collection));
if(readPreference.isSlaveOk()){
LOG.trace("Routing call to secondary for fetching children from [{}] to [{}]", fromKey, toKey);
}
cursor.setReadPreference(readPreference);