private PlanNode reserveMemoryForSeriesSourceNode(final SeriesSourceNode sourceNode) {
    this.context.reserveMemoryForFrontEnd(
        MemoryEstimationHelper.getEstimatedSizeOfAccountableObject(sourceNode));
    return sourceNode;
  }
There could be a lot of SeriesSourceNodes if there are too many series involved in one query.
We need to check the memory used by SeriesSourceNodes.(Number of other PlanNodes are rather
small compared to SourceNodes and could be safely ignored for now.)
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/planner/LogicalPlanBuilder.java