Query optimizer

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  • Unfortunately there is a lack of effective data management tools that can help users in managing such data and in ap- plying models, forcing them to use external tools for this purpose. Scientists, for instance, typically import the raw data into an analysis package such as Matlab, where they apply various models to the data. Once the data has been filtered, they typically process it further using customized programs that are often quite similar to database queries (e.g.

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  • (BQ) Part 1 book "Database system concepts" has contents: Introduction to the relational model, introduction to SQL, advanced SQL, intermediate SQL, formal relational query languages, database design and the E-R Model, indexing and hashing, relational database design, query processing, query optimization,...and other contents.

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  • Query processing presents about an overview of query processing; fast access paths; tranformation rules; algebra based optimization; Example of Execution plan; Cost of evaluating a query; Search space of query optimization.

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  • Database System: Chapter 10 - Query Processing and Optimization Introduction to Query Processing, Translating SQL Queries into Relational Algebra, Translating SQL Queries into Relational Algebra, Using Selectivity and Cost Estimates in Query Optimization, Overview of Query Optimization in Oracle.

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  • Queries not running fast enough? Tired of the phone calls from frustrated users? Grant Fritchey’s book SQL Server 2012 Query Performance Tuning is the answer to your SQL Server query performance problems. The book is revised to cover the very latest in performance optimization features and techniques. It is current with SQL Server 2012. It provides the tools you need to approach your queries with performance in mind.

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  • Contents at a Glance 1 Troubleshooting Database and Server Performance 2 Analyzing Queries 3 Failure Diagnosis 4 Disaster Recovery 5 Performance Monitoring 6 Database Maintenance 7 SQL Server Integration Services 8 Design Data Integrity 9 Business Requirements 10 Replication

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  • Extent of knowledge sharing: Related to the above problem is the question of how much knowledge is available to the system during its query optimization process. In particular, the first step in choosing a query evaluation strategy is likely to be identifying which nodes have materialized views that can speed query processing. A simple technique would be to use a centralized catalog of all available views and their locations, analogous to the central directory used by Napster. Yet this model introduces a single point of failure and a potential scalability bottleneck.

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  • The Greenplum Database parallel query optimizer (Figure 6) is responsible for converting SQL or MapReduce into a physical execution plan. It does this by using a cost-based optimization algorithm to evaluate a vast number of potential plans and select the one that it believes will lead to the most efficient query execution. Unlike a traditional query optimizer, Greenplum’s optimizer takes a global view of execution across the cluster, and factors in the cost of moving data between nodes in any candidate plan.

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  • Statistical language modeling (SLM) has been used in many different domains for decades and has also been applied to information retrieval (IR) recently. Documents retrieved using this approach are ranked according their probability of generating the given query. In this paper, we present a novel approach that employs the generalized Expectation Maximization (EM) algorithm to improve language models by representing their parameters as observation probabilities of Hidden Markov Models (HMM).

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  • Giới thiệu Trong bài đầu tiên của loạt bài này, Điều chỉnh SQL với Optim Query Tuner, Phần 1: Tìm hiểu về các đường dẫn truy cập, đã giới thiệu khái niệm về một đường dẫn truy cập. Với một câu lệnh SQL cụ thể, thường có nhiều sự lựa chọn đường dẫn truy cập, và các đường dẫn truy cập khác nhau thường có đặc điểm hiệu năng khác nhau.

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  • Database Management Systems: Chapter 3 - Algorithms for Query Processing and Optimization Introduction to Query Processing; Translating SQL Queries into Relational Algebra; Algorithms for External Sorting; Algorithms for SELECT and JOIN Operations;...

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  • This chapter describes the process by which queries are executed efficiently by a database system. Query processing refers to the range of activities involved in extracting data from a database. The activities include translation of queries in high-level database languages into expressions that can be used at the physical level of the file system, a variety of query-optimizing transformations, and actual evaluation of queries.

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  • Chapter 13 describes how queries are optimized. This chapter presents the following content: Transformation of relational expressions, catalog information for cost estimation, statistical information for cost estimation, cost-based optimization, dynamic programming for choosing evaluation plans, materialized views.

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  • This paper proposes a density optimal method, named as DO-TPR*-tree, which improves the performance of the original TPR*-tree significantly. In this proposed method, the search algorithm will enforce firing up MBR adjustment on a node, if the condition, based on density optimal for the area of its MBR, is satisfied at a query time.

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  • This document first began as an effort to help teams within Google, but we thought it'd be just as useful to webmasters that are new to the topic of search engine optimization and wish to improve their sites' interaction with both users and search engines. Although this guide won't tell you any secrets that'll automatically rank your site first for queries in Google (sorry!), following the best practices outlined below will make it easier for search engines to crawl, index and understand your content....

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  • The Oracle database engine has become a huge piece of software. This not only means that a single human can no longer be roficient in using all the features provided in recent versions, but it also means that some of them will rarely be used. Actually, in most situations, it is enough to know and take advantage of a limited number of core features in order to use the Oracle database engine efficiently and successfully.

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  • Part III Beyond Relational creating tables with XML columns, and allows declaring XML variables and using them as parameters and return values. XQuery is a W3C-recommended language created to query and format XML documents. XQuery can be used to query XML documents just like a SQL query is used to retrieve information from relational tables. The XML data type implements a limited subset of the XQuery specification and a T-SQL query can use XQuery to retrieve information from XML columns or variables.

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  • In modern agriculture, farmers continuously face a battle to achieve products in high yields and better quality to feed an ever increasing world population (Stetter & Lieb, 2000). The optimization of agriculture techniques demands, along with other requirements, the application of crop protection agents to control a variety of diseases and pests, among which are weeds. Weeds compete with crops for nutrients, water, and physical space, may harbor insect and disease pests, and are thus capable of greatly undermining both crop quality and yield.

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  • In the surnmero f 1997, whent he Federal ReserveB anko f Bostons elected the topic for its fortysecond annual economicc onference, manyp undits werea sking: "Is the business cycle dead, or at least permanently dampened?"B y the time the Bank’s conference convenedi n June 1998, the same pundits queried: "What caused the massive recessions in Asia?" and "Can the United States remain ’an oasis of prosperity,’ as Fed Chairman Alan Greenspan termed it, while economiesw orldwidea re under siege from financial crises?" Howq uickly things change! BeyondS hocks:W hatC ausesB usiness Cycles ? t...

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  • A query expresses in a high-level language like SQL must first be scanned, parsed, and validated. • Once the above steps are completed, an internal representation of the query is created. Typically this is either a tree or graph structure, called a query tree or query graph. • Using the query tree or query graph the RDBMS must devise an execution strategy for retrieving the results from the internal files. • For all but the most simple queries, several different execution strategies are possible. The process of choosing a suitable execution strategy is called query optimization....

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