H ibernate是连接Java对象模型和关系数据模型的桥梁。对于查询操作繁复的系统而言,良好的缓存管理机制和合理的缓存应用模式往往是性能提升的关键。首先对H ibernate持久层的二级缓存机制进行较为详细的分析,然后通过提高QueryKey匹配...H ibernate是连接Java对象模型和关系数据模型的桥梁。对于查询操作繁复的系统而言,良好的缓存管理机制和合理的缓存应用模式往往是性能提升的关键。首先对H ibernate持久层的二级缓存机制进行较为详细的分析,然后通过提高QueryKey匹配效率对缓存进行优化,从而有效地提高了SQL的比较效率。展开更多
Due to the proliferation of Internet and Intranet,the distributed storage systems have received a lot of attention. These systems span a large number of machines and store huge amount of data for a lot of users.In the...Due to the proliferation of Internet and Intranet,the distributed storage systems have received a lot of attention. These systems span a large number of machines and store huge amount of data for a lot of users.In the distributed storage systems,a row can be directly accessed using a row key.We concentrate on a problem of efficient processing of queries whose predicate is on a column but not a row key.In this paper,we present a cache management technique,called DICE which maintains query results of range queries to support the next range queries.To accelerate the search time of the cached query results,we use modified Interval Ski Lists.In addition,we devise a novel cache replacement policy since DICE maintains an interval rather than a data item.Since our cache replacement policy considers the properties of intervals,our proposed technique is more efficient than traditional buffer replacement algorithms.Our experimental result demonstrates the efficiency of our proposed technique.展开更多
Our study introduces a novel distributed query plan refinement phase in an enhanced architecture of distributed query processing engine （DQPE）. Query plan refinement generates potentially efficient distributed query...Our study introduces a novel distributed query plan refinement phase in an enhanced architecture of distributed query processing engine （DQPE）. Query plan refinement generates potentially efficient distributed query plan by reusable aggregate query shipping （RAQS） approach. The approach improves response time at the cost of pre-processing time. If the overheads could not be compensated by query results reusage, RAQS is no more favorable. Therefore a globM cost estimation model is employed to get proper operators： RR_Agg, R_Agg, or R_Scan. For the purpose of reusing results of queries with aggregate function in distributed query processing, a multi-level hybrid view caching （HVC） scheme is introduced. The scheme retains the advantages of partial match and aggregate query results caching. By our solution, evaluations with distributed TPC-H queries show significant improvement on average response time.展开更多
To improve efficiency of search engines, the query result cache has drawn much attention re- cently. According to the query processing and user＇s query logs locality, a new hybrid result cache strategy which associat...To improve efficiency of search engines, the query result cache has drawn much attention re- cently. According to the query processing and user＇s query logs locality, a new hybrid result cache strategy which associates with caching heat and worth is proposed to compute cache score in accord- ance with cost-aware strategies. Exactly, query repeated distance and query length factor are utilized to improve the static result policy, and the dynamic policy is adjusted by the caching worth. The hy- brid result cache is implemented in term of the document content and document ids （docIds） se- quence. Based on a score format and the new hybrid structure, an initial algorithm and a new rou- ting algorithm are designed for result cache. Experiments＇ results show that the improved caching policies decrease the average response time effectively, and increase the system throughput signifi- cantly. By choosing comfortable combination of page cache and docIds cache, the new hybrid cac- hing strategy almost reduces more than 20% of the only cache and docId-only cache. average query time compared with the basic page-展开更多
基金supported by National Research Foundation of Korea under Grant No.2010-0016165supported by the IT R&D Program of MIC/IITA under Grant No.2007-S-016-02.
文摘Due to the proliferation of Internet and Intranet,the distributed storage systems have received a lot of attention. These systems span a large number of machines and store huge amount of data for a lot of users.In the distributed storage systems,a row can be directly accessed using a row key.We concentrate on a problem of efficient processing of queries whose predicate is on a column but not a row key.In this paper,we present a cache management technique,called DICE which maintains query results of range queries to support the next range queries.To accelerate the search time of the cached query results,we use modified Interval Ski Lists.In addition,we devise a novel cache replacement policy since DICE maintains an interval rather than a data item.Since our cache replacement policy considers the properties of intervals,our proposed technique is more efficient than traditional buffer replacement algorithms.Our experimental result demonstrates the efficiency of our proposed technique.
基金partially supported by the National Basic Research 973 Program of China under Grant No. 2005CB321807the National High Technology Rresearch and Development 863 Program of China under Grant Nos. 2006AA01A106 and 2006AA04Z158.
文摘Our study introduces a novel distributed query plan refinement phase in an enhanced architecture of distributed query processing engine （DQPE）. Query plan refinement generates potentially efficient distributed query plan by reusable aggregate query shipping （RAQS） approach. The approach improves response time at the cost of pre-processing time. If the overheads could not be compensated by query results reusage, RAQS is no more favorable. Therefore a globM cost estimation model is employed to get proper operators： RR_Agg, R_Agg, or R_Scan. For the purpose of reusing results of queries with aggregate function in distributed query processing, a multi-level hybrid view caching （HVC） scheme is introduced. The scheme retains the advantages of partial match and aggregate query results caching. By our solution, evaluations with distributed TPC-H queries show significant improvement on average response time.
基金Supported by the National Natural Science Foundation of China(No.61173024)
文摘To improve efficiency of search engines, the query result cache has drawn much attention re- cently. According to the query processing and user＇s query logs locality, a new hybrid result cache strategy which associates with caching heat and worth is proposed to compute cache score in accord- ance with cost-aware strategies. Exactly, query repeated distance and query length factor are utilized to improve the static result policy, and the dynamic policy is adjusted by the caching worth. The hy- brid result cache is implemented in term of the document content and document ids （docIds） se- quence. Based on a score format and the new hybrid structure, an initial algorithm and a new rou- ting algorithm are designed for result cache. Experiments＇ results show that the improved caching policies decrease the average response time effectively, and increase the system throughput signifi- cantly. By choosing comfortable combination of page cache and docIds cache, the new hybrid cac- hing strategy almost reduces more than 20% of the only cache and docId-only cache. average query time compared with the basic page-
