@Override
  public List<RowData> get(RowData key) throws IOException {
    Optional<RowData> record = recordState.get(key);
    return record.map(Collections::singletonList).orElse(Collections.emptyList());
  }
Use a unique index to lookup. Working for the situation where the join keys include the
mixed-format table's primary keys.
amoro-format-mixed/amoro-mixed-flink/amoro-mixed-flink-common/src/main/java/org/apache/amoro/flink/lookup/UniqueIndexTable.java