protected List<DatabaseObject> mergeDatabaseObjects(List<DatabaseObject> objects) { int maxIdx = -1; for (DatabaseObject object : objects) { maxIdx = Math.max(maxIdx, object.getOrder()); } final List<DatabaseObject> orderedObjects = createListAndFillNull(maxIdx); final List<DatabaseObject> unorderedObjects = new ArrayList<>(); final List<DatabaseObject> mergedObjects = new ArrayList<>(); for (DatabaseObject object : objects) { if (object.getOrder() > -1) { int objIdx = object.getOrder(); if (objIdx < orderedObjects.size() && orderedObjects.get(objIdx) != null) { throw new TajoInternalError( "This catalog configuration contains duplicated order of DatabaseObject"); } orderedObjects.add(objIdx, object); } else { unorderedObjects.add(object); } } for (DatabaseObject object : orderedObjects) { if (object != null) { mergedObjects.add(object); } } for (DatabaseObject object : unorderedObjects) { if (object != null) { mergedObjects.add(object); } } return mergedObjects; }