public synchronized boolean forceAllocateFreeMemoryForOperators(long memoryInBytes) {
    // TODO @spricoder: consider a better way
    if (OPERATORS_MEMORY_BLOCK.getFreeMemoryInBytes() - memoryInBytes
        <= MIN_REST_MEMORY_FOR_QUERY_AFTER_LOAD) {
      return false;
    } else {
      OPERATORS_MEMORY_BLOCK.forceAllocateWithoutLimitation(memoryInBytes);
      return true;
    }
  }
Used to plan a fragment instance. One fragment instance could be split into multiple pipelines so
that a fragment instance could be run in parallel, and thus we can take full advantages of
multi-cores.
iotdb-core/datanode/src/main/java/org/apache/iotdb/db/queryengine/plan/planner/LocalExecutionPlanner.java