Adapting Materialized Views after Redefinitions: Techniques and a Performance Study

We consider a variant of the view maintenance problem: How does one keep a materialized view up-to-date when the view definition itself changes? Can one do better than recomputing the view from the base relations? Traditional view maintenance tries to maintain the materialized view in response to modifications to the base relations; we try to ``adapt'' the view in response to changes in the view definition. Such techniques are needed for applications where the user can change queries dynamically and see the changes in the results fast. Data archaeology, data visualization, and dynamic queries are examples of such applications. We consider all possible redefinitions of SQL\Select-\From-\Where-\Groupby-\Having, \Union, and \Minus\ views, and show how these views can be adapted using the old materialization for the cases where it is possible to do so. We identify extra information that can be kept with a materialization to facilitate redefinition.Multiple simultaneous changes to a view can be handled without necessarily materializing intermediate results. We identify guidelines for users and database administrators that can be used to facilitate efficient view adaptation. We perform a systematic experimental evaluation of our proposed techniques. Our evaluation indicates that adaptation is more efficient than rematerialization in most cases. Certain adaptation techniques can be up to1,000 times better. We also point out the physical layouts that can benefit adaptation

Optimized Generation and Maintenance of Materialized View using Adaptive Mechanism

Data Warehouse is storage of enormous amount of data gathered from multiple data sources, which is mainly used by managers for analysis purpose. Hence to make this data available in less amount of time is essential. Using Materialize view we can have result of query in less amount of time compared to access the same from base tables. To materialize all of the views is not possible since it requires storage space and maintenance cost. So it is required to select materialized view which minimizes response time of query and cost of maintenance. In this paper, effective approach is suggested for selection and maintenance of materialize view. DOI: 10.17762/ijritcc2321-8169.15050

Using Fuzzy Linguistic Representations to Provide Explanatory Semantics for Data Warehouses

A data warehouse integrates large amounts of extracted and summarized data from multiple sources for direct querying and analysis. While it provides decision makers with easy access to such historical and aggregate data, the real meaning of the data has been ignored. For example, "whether a total sales amount 1,000 items indicates a good or bad sales performance" is still unclear. From the decision makers' point of view, the semantics rather than raw numbers which convey the meaning of the data is very important. In this paper, we explore the use of fuzzy technology to provide this semantics for the summarizations and aggregates developed in data warehousing systems. A three layered data warehouse semantic model, consisting of quantitative (numerical) summarization, qualitative (categorical) summarization, and quantifier summarization, is proposed for capturing and explicating the semantics of warehoused data. Based on the model, several algebraic operators are defined. We also extend the SQL language to allow for flexible queries against such enhanced data warehouses

Ronciling Differences

In this paper we study a problem motivated by the management of changes in databases. It turns out that several such change scenarios, e.g., the separately studied problems of view maintenance (propagation of data changes) and view adaptation (propagation of view definition changes) can be unified as instances of query reformulation using views provided that support for the relational difference operator exists in the context of query reformulation. Exact query reformulation using views in positive relational languages is well understood, and has a variety of applications in query optimization and data sharing. Unfortunately, most questions about queries become undecidable in the presence of difference (or negation), whether we use the foundational set semantics or the more practical bag semantics. We present a new way of managing this difficulty by defining a novel semantics, Z- relations, where tuples are annotated with positive or negative integers. Z-relations conveniently represent data, insertions, and deletions in a uniform way, and can apply deletions with the union operator (deletions are tuples with negative counts). We show that under Z-semantics relational algebra (R A) queries have a normal form consisting of a single difference of positive queries, and this leads to the decidability of their equivalence.We provide a sound and complete algorithm for reformulating R A queries, including queries with difference, over Z-relations. Additionally, we show how to support standard view maintenanc

Incremental Refresh Materialized Query Table(Mqt) Memanfaatkan Staging Table Untuk Optimasi Query Execution Time Dan Resources Yang Digunakan

Materialized Query Table (MQT) menyimpan data dari query yang sering digunakan sehingga pengguna dapat memperoleh data tanpa harus melakukan komputasi ulang. Hal ini dapat meningkatkan performa sistem dengan mengurangi biaya query. Data didalam MQT harus diperbarui secara berkala agar tidak menjadi usang ketika terjadi perubahan pada tabel induk. Ada 2 (dua) macam mekanisme pembaruan yang umum digunakan, yaitu full refresh dan incremental refresh. Full refresh mengkomputasi ulang seluruh data dari tabel induk. Sedangkan incremental refresh hanya memproses data-data yang mengalami perubahan dengan memanfaatkan staging table. Staging table berperan menyimpan perubahan data (delta) pada tabel induk untuk mendukung proses incremental refresh. Penelitian ini mensimulasikan dan membandingkan performa dari full refresh dengan incremental refresh untuk mengetahui dampak keduanya terhadap waktu eksekusi query dan penggunaan sumber daya (I/O dan CPU). Data yang digunakan merupakan data asli yang berasal dari penelitian sebelumnya dan data dummy hasil generate sistem untuk mendukung penelitian. Hasil pengujian menunjukkan bahwa incremental refresh meningkatkan performa lebih dari 10x lipat pada waktu eksekusi query dan meningkatkan lebih dari 50x lipat pada penggunaan sumber daya dibandingkan dengan full refresh

The Application of Object-Oriented Views to an Engineering Environment.

With the increasing popularity of object-oriented technology, object-oriented database systems are being used in design environments as central repositories. In this thesis, we investigate the role of versioning and the characteristics of design databases in design environments. In an effort to improve the configuration management scheme in a design environment, we also investigate the use of database views as a possible configuration tool. We propose a unified version management scheme that facilitates cooperative team work and show that the use of database views provides a powerful configuration management scheme for a design environment

Manejando la evolución de aplicaciones web con adaptación

La complejidad es una característica inherente al software desde sus orígenes, e igualmente característico es que dicha complejidad crece en consonancia con el universo de roles que desempeña en la actualidad. Permanentemente aparecen nuevas ideas, metodologías y herramientas para hacerle frente, que atacan diferentes aspectos del ciclo de vida de desarrollo de software, o más aún, los enfoques del ciclo mismo. Gran parte de la complejidad tiene que ver con la necesidad de estar preparado para adecuarse permanentemente a nuevos requerimientos. Reusabilidad, encapsulamiento, binding dinámico, han sido respuestas con la que el paradigma de objetos ha respondido a esta problemática y junto a estas, la separación de responsabilidades de un conjunto de parte que cooperan entre si, tiene un lugar destacado como lo demuestra el pattern modelo vista controlador originado en Smalltalk separando y desacoplando tareas de interfase y del modelo de la aplicación. Más allá de interfases y aplicaciones, la separación de responsabilidades y el desacoplamiento entre clases, desde un punto de vista más general, es abordada por una serie de design patterns así como su contraparte necesaria, el aspecto cooperativo entre las mismas. En este último aspecto, el pattern Observer aborda la problemática de un conjunto indeterminado de objetos observadores que requieren ser notificados y actualizados respecto de cambios de estado de otro objeto determinado. El pattern permite la evolución de los observadores, incluso el agregado o eliminación de algunos de ellos sin interferir en el objeto observado, lo que permite disminuir el impacto que cambios de una parte del software, tales como vistas u observadores pueden requerir sobre otra, tales como el modelo o elementos observados. Como cualquier disciplina, el software, y particularmente su diseño, evoluciona a medida que se sistematizan aspectos del mismo. Los design patterns constituyen un hito sustancial en la sistematización de soluciones a problemas que se repiten en el diseño de diversas aplicaciones. Sobre este hito se desarrolla otro, el refactoring o reestructuración de programas orientados a objeto, que tiene por objetivo introducir en forma automática mejoras, en especial design patterns en el código, sin modificar su comportamiento. La reestructuración es un paso previo a la introducción de nuevas prestaciones del software existente.Facultad de Informátic

Adapting materialized views after redefinitions

We consider a variant of the view maintenance problem: How does one keep a materialized view up-to-date when the view definition itself changes? Can one do better than recomputing the view from the base relations? Traditional view maintenance tries to maintain the materialized view in response to modifications to the base relations; we try to “adapt ” the view in response to changes in the view definition. Such techniques are needed for applications where the user can change queries dynamically and see the changes in the results fast. Data archaeology, data visualization, and dynamic queries are examples of such applications. We consider all possible redefinitions of SQL SELECT-FROM-UHERE-GROUPBY, UNION, and EXCEPT views, and show how these views can be adapted using the old materialization for the cases where it is possible to do so. We identify extra information that can be kept with a materialization to facilitate redefinition. Multiple simultaneous changes to a view can be handled without necessarily materializing intermediate results. We iden-tify guidelines for users and database administrators that can be used to facilitate efficient view adaptation.