Synonyms Query evaluation ; Query planning and execution Definition In an (object) relational database management system (DBMS) query processing comprises all steps of processing a user submitted query including its execution to compute the requested result. Usually, a user query – for example a ...
Query processing refers to the sequence of steps that the DBMS will initiate to process the query. Queries can be broadly divided into two categories: single-scan queries and multiscan queries. In a single-scan query, a record (tuple) in the table (relation) being queried has to be ...
由于SQL是声明式语言(declarative),用户只告诉了DBMS想要获取什么,但没有指出如何计算。因此,DBMS需要将SQL语句转换成可执行的查询计划(Query Plan)。但是对同样的数据可以有多种查询方案,性能也差距很大,查询优化器(Query Optimizer)的任务就是从给定的查询中选择一个最优的方案。 最早的查询优化器实现是IBM在1970s...
By selecting the optimal execution plan for processing data, Query Optimization significantly improves database performance and minimizes latency. FAQs What is Query Optimization? Query Optimization is an aspect of DBMS that determines the most efficient way to execute a given query. Why is Query Opti...
Transaction Processing Performance Council, TPC Benchmark D (Decision Support) Standard Specification Revision 1.1, December, 1995 R.H.Wolniewicz and G.Graefe, Algebraic Optimization of Computations over Scientific Databases,Proc. Intl’ Conf. On Very Large Data Bases, Dublin, Ireland, August 1993,...
关键词:Query Optimization, Cost Model, MPP, Parallel Processing 前言 大数据带来了对查询优化的新兴兴趣,因为一种新型的数据管理系统在可扩展性、可用性和处理能力方面推动了前所未有的突破(例如,[9,18,20,21]),这使得数百TB甚至PB级别的大型数据集可以通过SQL或类似SQL的接口轻松进行分析。优化器的好坏差异一直...
Oracle Database Conceptsfor an overview of SQL processing 4.1.3.2Query Subplans For each query block, the optimizer generates a query subplan. The database optimizes query blocks separately from the bottom up. Thus, the database optimizes the innermost query block first and generates a subplan ...
Sketch Techniques for Approximate Query Processing 热度: Similarity-awareQueryProcessingandOptimization * YasinN.Silva Supervisedby:WalidG.Aref DepartmentofComputerScience,PurdueUniversity {ysilva,aref}@cs.purdue.edu ABSTRACT Manyapplicationscenarios,e.g.,marketinganalysis,sensor ...
Int. Conf. on Parallel and Distributed Information Systems, Florida, USA, December 1991. Google Scholar C. Chachaty, P. Borla-Salamet, M. Ward, “A Compositional Approach for the Design of a Parallel Query Processing Language”, Int. Conf. on Parallel Architectures and Language Europe, ...
in DBMSs, and Freytag [Fre87] and Graefe/DeWitt [GD87] have addressed some of the difficulties of extensible query optimization. The difficulty of specifying the repertoire of alternative QEPs in a high-level, declarative manner has prompted Frey- ...