@Override
  public int hashCode() {
    return Objects.hash(type, memTableInfos);
  }
Checkpoint is the basic element of .checkpoint file, including type, number of memTables, and
brief information of each memTable.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/storageengine/dataregion/wal/checkpoint/Checkpoint.java