@Override
  public long calculateMaxPeekMemory() {
    long maxPeekMemory = 0;
    long childrenMaxPeekMemory = 0;
    for (Operator child : children) {
      childrenMaxPeekMemory =
          Math.max(
              childrenMaxPeekMemory, maxPeekMemory + child.calculateMaxPeekMemoryWithCounter());
      maxPeekMemory +=
          (child.calculateMaxReturnSize() + child.calculateRetainedSizeAfterCallingNext());
    }

    maxPeekMemory += calculateMaxReturnSize();
    return Math.max(maxPeekMemory, childrenMaxPeekMemory);
  }
This field indicates each data type for output columns(not including time column) of
TimeJoinOperator its size should be equal to outputColumnCount.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/execution/operator/process/join/FullOuterTimeJoinOperator.java