@Override
  public long ramBytesUsed() {
    return INSTANCE_SIZE
        + MemoryEstimationHelper.getEstimatedSizeOfAccountableObject(operatorContext)
        + RamUsageEstimator.sizeOf(inputIndex)
        + RamUsageEstimator.sizeOf(noMoreTsBlocks)
        + (children == null
            ? 0
            : children.stream()
                .mapToLong(MemoryEstimationHelper::getEstimatedSizeOfAccountableObject)
                .sum())
        + tsBlockBuilder.getRetainedSizeInBytes();
  }
prepare next batch

@return true if need to break current loop, otherwise false
@throws Exception errors happened while fetching next batch data
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/execution/operator/process/last/LastQueryMergeOperator.java