final String docId = DocumentUtil.getValue(doc, fessConfig.getIndexFieldId(), String.class);
            throw new FessSystemException("configId is null in document. docId: " + docId);
        }
        if (configId.length() < 2) {
            throw new FessSystemException("Invalid configId length: " + configId + ". ConfigId must be at least 2 characters long.");
        }