return "";
            }

            @Override
            public String getIndexFieldId() {
                return "_id";
            }

            @Override
            public String getIndexFieldVersion() {
                return "_version";
            }

            @Override
            public String getIndexFieldSeqNo() {
                return "_seq_no";
            }

            @Override

                if (!newId.equals(oldId)) {
                    entity.put(fessConfig.getIndexFieldId(), newId);
                    entity.remove(fessConfig.getIndexFieldVersion());
                    final Long seqNo = (Long) entity.remove(fessConfig.getIndexFieldSeqNo());
                    final Long primaryTerm = (Long) entity.remove(fessConfig.getIndexFieldPrimaryTerm());

     * The value is, e.g. _version <br>
     * comment: Field name for version in the index.
     * @return The value of found property. (NotNull: if not found, exception but basically no way)
     */
    String getIndexFieldVersion();

    /**
     * Get the value for the key 'index.field.seq_no'. <br>
     * The value is, e.g. _seq_no <br>
     * comment: Field name for sequence number in the index.