public void setFirstFileVersionId(long firstFileVersionId) {
    this.firstFileVersionId = firstFileVersionId;
  }
MemTableInfo records brief info of one memTable, including memTable id, tsFile path, and .wal
file version id of its first {@link WALEntry}.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/storageengine/dataregion/wal/checkpoint/MemTableInfo.java