In parallel real-time database systems, concurrency control protocols must satisfy time constraints as well as the integrity constraints. The authors present a validation concurrency control(VCC) protocol, which can e...In parallel real-time database systems, concurrency control protocols must satisfy time constraints as well as the integrity constraints. The authors present a validation concurrency control(VCC) protocol, which can enhance the performance of real-time concurrency control mechanism by reducing the number of transactions that might miss their deadlines, and compare the performance of validation concurrency control protocol with that of HP2PL(High priority two phase locking) protocol and OCC-TI-WAIT-50(Optimistic concurrency control-time interval-wait-50) protocol under shared-disk architecture by simulation. The simulation results reveal that the protocol the author presented can effectively reduce the number of transactions restarting which might miss their deadlines and performs better than HP2PL and OCC-TI-WAIT-50. It works well when arrival rate of transaction is lesser than threshold. However, due to resource contention the percentage of missing deadline increases sharply when arrival rate is greater than the threshold.展开更多
随着移动设备和物联网技术的普及,时空数据的收集和分析变得越来越重要。轨迹预测,尤其是实时轨迹预测,对于许多应用领域如智能交通和城市规划等至关重要。现有的轨迹预测方法往往无法在保证预测准确性的同时满足实时性的要求,且实时数...随着移动设备和物联网技术的普及,时空数据的收集和分析变得越来越重要。轨迹预测,尤其是实时轨迹预测,对于许多应用领域如智能交通和城市规划等至关重要。现有的轨迹预测方法往往无法在保证预测准确性的同时满足实时性的要求,且实时数据通常是不完整或带有噪声的,要求预测算法必须能够适应不完全的轨迹信息。基于此,提出了一种基于时空数据库的实时启发式轨迹预测模型(Real-time Heuristic Trajectory Prediction Based on Spatio-Temporal Databases,RHTP-STD)。RHTP-STD利用MobilityDB数据库平台存储和管理轨迹数据,通过图构建算法将轨迹数据转换为时空图。RHTP-STD采用启发式算法,融合历史和实时数据,快速预测移动对象的未来轨迹。实验结果表明,RHTP-STD在Argoverse数据集上的预测准确性和实时性均优于现有方法。讨论所提方法在不同应用场景中的适用性,提出了未来的研究方向。展开更多
并发控制协议是确保数据库性能目标的一个关键问题,对移动分布式实时数据库(Mobile Distributed Real-time DataBase,简称MDRTDB)并发控制协议-分布式高优先级两段锁协议(Distributed High Priority two Phrase Locking protocol,简称DH...并发控制协议是确保数据库性能目标的一个关键问题,对移动分布式实时数据库(Mobile Distributed Real-time DataBase,简称MDRTDB)并发控制协议-分布式高优先级两段锁协议(Distributed High Priority two Phrase Locking protocol,简称DHP-2PL)从两个方面做出了改进:一是采用动态优先级分配策略,能够缩短实时事务执行的等待时间和避免饥饿现象的产生;二是为了增加并发度在加锁机制中使用混合加锁粒度,同时能够减少加锁开销。最后通过模拟应用环境的性能测试表明,这两方面的改进更好地满足了事务截止期的要求,提高了移动实时事务的成功率。展开更多
文摘In parallel real-time database systems, concurrency control protocols must satisfy time constraints as well as the integrity constraints. The authors present a validation concurrency control(VCC) protocol, which can enhance the performance of real-time concurrency control mechanism by reducing the number of transactions that might miss their deadlines, and compare the performance of validation concurrency control protocol with that of HP2PL(High priority two phase locking) protocol and OCC-TI-WAIT-50(Optimistic concurrency control-time interval-wait-50) protocol under shared-disk architecture by simulation. The simulation results reveal that the protocol the author presented can effectively reduce the number of transactions restarting which might miss their deadlines and performs better than HP2PL and OCC-TI-WAIT-50. It works well when arrival rate of transaction is lesser than threshold. However, due to resource contention the percentage of missing deadline increases sharply when arrival rate is greater than the threshold.
文摘随着移动设备和物联网技术的普及,时空数据的收集和分析变得越来越重要。轨迹预测,尤其是实时轨迹预测,对于许多应用领域如智能交通和城市规划等至关重要。现有的轨迹预测方法往往无法在保证预测准确性的同时满足实时性的要求,且实时数据通常是不完整或带有噪声的,要求预测算法必须能够适应不完全的轨迹信息。基于此,提出了一种基于时空数据库的实时启发式轨迹预测模型(Real-time Heuristic Trajectory Prediction Based on Spatio-Temporal Databases,RHTP-STD)。RHTP-STD利用MobilityDB数据库平台存储和管理轨迹数据,通过图构建算法将轨迹数据转换为时空图。RHTP-STD采用启发式算法,融合历史和实时数据,快速预测移动对象的未来轨迹。实验结果表明,RHTP-STD在Argoverse数据集上的预测准确性和实时性均优于现有方法。讨论所提方法在不同应用场景中的适用性,提出了未来的研究方向。
基金山东省科技公关计划(the Key Technologies R&D Program of Shandong ProvinceChina under Grant No.2004GG2205108)。
文摘并发控制协议是确保数据库性能目标的一个关键问题,对移动分布式实时数据库(Mobile Distributed Real-time DataBase,简称MDRTDB)并发控制协议-分布式高优先级两段锁协议(Distributed High Priority two Phrase Locking protocol,简称DHP-2PL)从两个方面做出了改进:一是采用动态优先级分配策略,能够缩短实时事务执行的等待时间和避免饥饿现象的产生;二是为了增加并发度在加锁机制中使用混合加锁粒度,同时能够减少加锁开销。最后通过模拟应用环境的性能测试表明,这两方面的改进更好地满足了事务截止期的要求,提高了移动实时事务的成功率。
