In this paper we motivate and describe materialized views, their applications, and the problems and techniques for their maintenance. We present a taxonomy of view maintenanceproblems basedupon the class of views considered, upon the resources used to maintain the view, upon the types of modi#cations to the base data that areconsidered during maintenance, and whether the technique works for all instances of databases and modi#cations. We describe some of the view maintenancetechniques proposed in the literature in terms of our taxonomy. Finally, we consider new and promising application domains that are likely to drive work in materialized views and view maintenance. 1 Introduction What is a view? A view is a derived relation de#ned in terms of base #stored# relations. A view thus de#nes a function from a set of base tables to a derived table; this function is typically recomputed every time the view is referenced. What is a materialized view? A view can be materialized by storin...

Efficient methods of processing unanticipated queries are a crucial prerequisite for the success of generalized database management systems. A wide variety of approaches to improve the performance of query evaluation algorithms have been proposed: logic-based and semantic transformations, fast implementations of basic operations, and combinatorial or heuristic algorithms for generating alternative access plans and choosing among them. These methods are presented in the framework of a general query evaluation procedure using the relational calculus representation of queries. In addition, nonstandard query optimization issues such as higher level query evaluation, query optimization in distributed databases, and use of database machines are addressed. The focus, however, is on query optimization in centralized database systems.

Database updates are small and incremental compared to database contents. It is therefore desirable that recomputations of active relational expressions -- such as views, derived data, integrity constraints, active queries, and monitors -- can be performed incrementally as well. We present an efficient algorithm for the incremental recomputation of active relational expressions based on finite differencing techniques. Database updates are modeled as incremental changes to database relations, and the algorithm derives, by update propagation, the minimal incremental relational expressions that need recomputation. The algorithm has applications in the maintenance of materialized views and derived data, the checking of integrity constraints, and the evaluation of active queries and monitors. Keywords--- Active Queries, Derived Data, Finite Differencing, Incremental Recomputation, Integrity Constraints, Monitors, Updates, Views I. Introduction Database management systems need to perform ...

Abstract We investigate the problem of incremental maintenance of an SQL view in the face of database updates, and show that it is possible to reduce the total time cost of view maintenance by materializing (and maintaining) additional views. We formulate the problem of determining the optimal set of additional views to materialize as an optimization problem over the space of possible view sets (which includes the empty set). The optimization problem is harder than query optimization since it has to deal with multiple view sets, updates of multiple relations, and multiple ways of maintaining each view set for each updated relation. We develop a memoing solution for the problem; the solution can be implemented using the expression DAG representation used in rule-based optimizers such as Volcano. We demonstrate that global optimization cannot, in general, be achieved by locally optimizing each materialized subview, because common subexpressions between different materialized subviews can allow nonoptimal local plans to be combined into an optimal global plan. We identify conditions on materialized subviews in the expression DAG when local optimization is possible. Finally, we provide a systematic space of heuristics that can be used to efficiently determine a useful set of additional views to materialize. Our results are particularly important for the efficient checking of assertions (complex integrity constraints) in the SQL-92 standard, since the incremental checking of such integrity constraints is known to be essentially equivalent to the view maintenance problem.

A systematic approach is given for deriving incremental programs from non-incremental programs written in a standard functional programming language. We exploit a number of program analysis and transformation techniques and domain-specific knowledge, centered around effective utilization of caching, in order to provide a degree of incrementality not otherwise achievable by a generic incremental evaluator. 1 Introduction Incremental programs take advantage of repeated computations on inputs that differ only slightly from one another, avoiding unnecessary duplication of common computations. Given a program f and a certain input change \Phi, a program f 0 that computes the value of f(x \Phi y) efficiently by making use of the value of f(x) is called an incremental version of f under \Phi. The parameter y can be regarded as a change ffix to the input x. Methods of incremental computation have widespread applications, e.g., loop optimizations in optimizing compilers [1, 24, 9, 10] and ...

Database programming requires knowledge of database semantics both to maintain database integrity and to explore more optimization opportunities. Automated programming of database transactions is desirable and feasible. In general, transactions use simple constructs and algorithms; specifications of database semantics are available; and transactions perform small incremental updates to database contents. Automated programming in such a restricted but well-understood and important domain is promising. We approach the synthesis of database transactions that preserve the validity of integrity constraints using deductive techniques. A transaction logic for a fairly expressive class of transactions is developed as the formalism within which the synthesis is conducted. Transactions are generated as the by-product of proving specifications in the logic. The Manna-Waldinger deductive-tableau system is extended with inference rules for the extraction of transactions from proofs, which require t...

We present an approach for integrating inter-object constraint maintenance seamlessly into an object-oriented database system. We develop a constraint compilation scheme that accepts declarative global specification of constraints, including relational integrity, referential integrity, and uniqueness requirements, and generates an efficient representation that permits localized processing. We demonstrate the feasibility of our approach by designing a constraint pre-processor for O*, the programming language interface to the Ode object-oriented database. 1.

Constraint validation has bcc?n difficult to imple-ment efficiently. The major reason for this difficulty lies in the state-dependent nature of integrity constraints and the rt~quiremcnt of both high-level spc&fication and cfficirnt runtimc cnforccmcnt. In this paper, we pro-pose a constraint reformulation approach to rfficicnt constraint validation. We also demonstrate how this knowledge-basrd constraint rcfornmlation can be natu-rally accomplished in the gcncral framework of problem reformulation with the technique of antecedent deriva-tion. We formalize thr reformulation of an integrity constraint as a tree-starch process where the search space is thtr set of all semantic-equivalent alternatives of the original constraint. We also develop control strate-gies and mcta-level rules for carrying out the search c?fficicntly. The major contribution of this work is a new promising approach to cfficirnt constraint valida-tiun and a general framework to accomplish it. 1.

This paper describes a transformational method applied to the core component of role-based access control (RBAC), to derive efficient implementations from a specification based on the ANSI standard for RBAC. The method is based on the idea of incrementally maintaining the result of expensive set operations, where a new method is described and used for systematically deriving incrementalization rules. We calculate precise complexities for three variants of efficient implementations as well as for a straightforward implementation based on the specification. We describe successful prototypes and experiments for the efficient implementations and for automatically generating efficient implementations from straightforward implementations.

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