scholarly journals Optimization of correlate subquery based on distributed database

2021 ◽  
Vol 39 (4) ◽  
pp. 909-918
Author(s):  
Chenyu Zhang ◽  
Wenjie Liu ◽  
Tianze Pang ◽  
Yantao Yue
Keyword(s):  
Query Optimization ◽  
Function Method ◽  
Data Communication ◽  
Distributed Database ◽  
Communication Overhead ◽  
Optimization Strategy ◽  
Join Queries ◽  
Accumulation Function ◽  
Low Efficiency ◽  
Disk Access

Subquery is widely used in database. It can be divided into related subquery and non-related subquery according to whether it is dependent on the table of the parent query. For related subqueries, it is necessary to take a tuple from the parent query before executing the subquery, that is, the content of the subquery needs to be repeatedly operated. Disk access costs of this strategy is very big, in the distributed database, because of data communication overhead, in the parent query yuan set is too low efficiency, therefore, for the class sub queries, on the basis of the optimization of the existing query strategy, combining with the characteristics of distributed database, put forward by the subquery on to join queries, eliminate redundant clauses in the subquery, eliminate accumulation function method based on distributed database query optimization strategy, and the effectiveness of the present optimization strategy is verified by experiment.

scholarly journals Assessment of Urban Water Supply System Based on Query Optimization Strategy

Complexity ◽  
2018 ◽  
Vol 2018 ◽  
pp. 1-10 ◽  
Author(s):  
Shibao Lu ◽  
Yizi Shang ◽  
Wei Li ◽  
Zhimin Wang
Keyword(s):  
Water Treatment ◽  
Water Supply ◽  
Query Optimization ◽  
Treatment Cost ◽  
Distributed Database ◽  
Urban Water ◽  
Optimization Strategy ◽  
Urban Water Supply ◽  
Treatment Efficiency ◽  
Water Treatment Cost

As a complicated water treatment system project, an urban water supply plays a significant role in enhancing ecological civilization construction, promoting social-economic sustainable development, and improving the living environment of humans. This paper has the goal of improving water treatment efficiency and reducing water treatment cost based on comparative studies by applying two types of distributed database query optimization methods, including the system for a distributed database (SDD-1) and all reduction algorithms. The approach involves the components of partial relations and deletes the database components that are unrelated to a query, using only attributes related to a query. Thereby, the realization process becomes simple, with a small amount of transmitted data. The results show that the validity and convenience of all reduction algorithms involve the whole query process. An algorithm is independent of the chart of static characteristics and can realize all reduction states without depending on analyzing the benefits from intermediate semijoin results, which will ultimately contribute to reductions in the transmission of useless data in the network and communication costs. Implementation of the query optimization strategy can improve water treatment efficiency, reduce water treatment cost, lower water treatment expense, and implement effective communication.

Research on Query Optimization Technology in Distributed Database

2012 ◽  
Vol 433-440 ◽  
pp. 3335-3339
Author(s):  
Bo Zhu Wu
Keyword(s):  
Query Processing ◽  
Query Optimization ◽  
Distributed Database ◽  
Query Time ◽  
Processing Technology ◽  
Database Query ◽  
Processing Program ◽  
Depth Study ◽  
Database Query Processing ◽  
Query Efficiency

Through the in-depth study of the existing distributed database query processing technology, this paper proposes a distributed database query processing program. This program optimizes the existing query processing, stores the commonly used query results according to the query frequency, to be directly used by the subsequent queries or used as intermediate query results, thus avoiding possible transmission of a large number of data, thereby reducing the query time and improving query efficiency.

scholarly journals A Strategy of Efficient and Accurate Cardinality Estimation Based on Query Result

2018 ◽  
Vol 36 (4) ◽  
pp. 768-777
Author(s):  
Jintao Gao ◽  
Zhanhuai Li ◽  
Wenjie Liu
Keyword(s):  
Big Data ◽  
Query Optimization ◽  
Cardinality Estimation ◽  
Estimation Strategy ◽  
Query Result ◽  
Original Table ◽  
Data Statistics ◽  
Low Efficiency

Cardinality estimation is an important component of query optimization. Its accuracy and efficiency directly decide effect of query optimization. Traditional cardinality estimation strategy is based on original table or sample to collect statistics, then inferring cardinality by collected statistics. It will be low-efficiency when handling big data; Statistics exist update latency and are gotten by inferring, which can not guarantee correctness; Some strategies can get the actual cardinality by executing some subqueries, but they do not keep the result, leading to low efficiency of fetching statistics. Against these problems, this paper proposes a novel cardinality estimation strategy, called cardinality estimation based on query result(CEQR). For keeping correctness of cardinality, CEQR directly gets statistics from query results, which is not related with data size; we build a cardinality table to store the statistics of basic tables and middle results under specific predicates. Cardinality table can provide cardinality services for subsequent queries, and we build a suit of rules to maintain cardinality table; To improve the efficiency of fetching statistics, we introduce the source aware strategy, which hashes cardinality item to appropriate cache. This paper gives the adaptability and deviation analytic of CEQR, and proves that CEQR is more efficient than traditional cardinality estimation strategy by experiments.

Remote Monitoring System of the Rivers and Lakes' Water Quality Based on GPRS and 3G Technology

2014 ◽  
Vol 898 ◽  
pp. 618-623
Author(s):  
Meng Xia An ◽  
Ji Ping Xu ◽  
Xiao Yi Wang ◽  
Jia Bin Yu ◽  
Hui Yan Zhang ◽  
...  
Keyword(s):  
Water Quality ◽  
Real Time ◽  
Monitoring System ◽  
Remote Monitoring ◽  
Data Communication ◽  
Water Quality Monitoring ◽  
Management Decision ◽  
Remote Monitoring System ◽  
Rivers And Lakes ◽  
Low Efficiency

In view of the methods on remote monitoring of the rivers and lakes water quality are relatively single and low efficiency in supervision at present, this page puts forward a kind of design method of the internet of things system about remote monitoring system based on GPRS/3G technology. The system can realize multi-point data integration, processing, integration and real-time results releasing, with GPRS/3G remote data communication technology as the core, and send the information accesses to the buoys placed on the waters surface, mobile intelligent instruments, and the water quality monitoring ark placed on the water bank via GPRS/3G module to the superior intelligence analysis system, which realizes the real-time display in the GIS map, water quality evaluation, bloom forecast, decision-making, etc. Practice has proved that this system is stable and reliable, and provided the effective monitoring of the rivers and lakes water quality and management decision of algae blooms emergency for the environmental protection department.

scholarly journals Query Optimization on Distributed Database Dengue Fever by Minimizing Attribute Involvement

2018 ◽  
Vol 14 (4) ◽  
pp. 466-476
Author(s):  
Slamet Sudaryanto Nurhendratno ◽  
Sudaryanto ◽  
Fikri Budiman ◽  
Maryani Setyowati
Keyword(s):  
Dengue Fever ◽  
Query Optimization ◽  
Distributed Database
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