src\backend\executor\execUtils.c：
uint64 PlanStateOperatorMemKB(const PlanState *ps)
{
	Assert(ps);
	Assert(ps->plan);
	uint64 result = 0;
	if (ps->plan->operatorMemKB == 0)
	{
		/**
		 * There are some statements that do not go through the resource queue and these
		 * plans dont get decorated with the operatorMemKB. Someday, we should fix resource queues.
		 */
		result = work_mem;
	}
	else
	{
		if (IsA(ps, AggState))
		{
			/* Retrieve all relinquished memory (quota the other node not using) */
			result = ps->plan->operatorMemKB + (MemoryAccounting_RequestQuotaIncrease() >> 10);
		}
		else
			result = ps->plan->operatorMemKB;
	}
	
	return result;
}