@Override
    public boolean isVirtual(MetaField metaField) {
        return true;
    }
the primary key must be "_id"

@see <a href="https://ververica.github.io/flink-cdc-connectors/release-2.1/content/connectors/mongodb-cdc.html#">MongoDB CDC Connector</a>
inlong-sort/sort-common/src/main/java/org/apache/inlong/sort/protocol/node/extract/MongoExtractNode.java