A. Gupta and I. S. Mumick. Maintenance of materialized views: Problems, techniques and applications. IEEE Data Engineering Bulletin, 18(2), June 1995. Special Issue on Materialized Views and Data Warehousing.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....view maintenance that assumes that views are de ned and maintained using the same language. Numerous algorithms exist dealing with fragments of relational algebra [2] full relational algebra [29, 13] bag (multiset) languages [12] languages with grouping and aggregation [16, 30] and others; see [15] for a survey. However, much less is known in the case when a view is de ned in one, more powerful language, and is maintained in another one, less powerful. Those papers that do consider this situation deal with the case when a recursive query is computable in polynomial time and de nable in a ....

....unary auxiliary relations. As pointed out in the introduction, proving bounds for maintenance with auxiliary relations of arity 2 and higher is probably beyond reach. Note also that in the algorithmic literature on view maintenance one typically considers maintenance without auxiliary data, see [2, 13, 12, 15, 16]. Another parameter of incremental maintenance is whether the value of auxiliary relations is the same for any sequence of updates that leads to a given database. It was shown in [7] that fewer queries can be incrementally maintained under this restriction. In what follows, we thus consider this ....

A. Gupta and I. S. Mumick. Maintenance of Materialized Views: Problems, Techniques, and Applications. IEEE Data Engineering Bulletin, Special Issue on Materialized Views and Data Warehousing, 18(2):3-19, June 1995.

....views are more frequent than the updates to the database, because frequently accessed views result in repetitive view construction. 1 Chapter 1. Introduction 2 The second method to implement views is the view materialization approach where the view is explicitly maintained as a stored relation [GM95] This method requires more storage than the query modification approach but its performance might be significantly better, especially if updates are less frequent than queries referring to the views. A database system should provide the option of materializing views. The choice of which views to ....

....beneficial than re evaluating the view. When one relation is completely deleted from the database, it is almost always better to re evaluate any join involving that relation. On the other hand, when the updates to the database are small, compared to the database itself, the principle of inertia [GM95] that small changes propagate small changes, seems to favor incremental evaluation of the join. However, we found that the cost of propagating small changes could be about the same as (or more than) the cost of evaluating the view again. Also, when the updates to the database are neither very ....

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A. Gupta and I.S. Mumick. Maintenance of Materialized Views: Problems, Techniques and Applications. Data Engineering, Special Issue on Materialized Views and Data Warehousing, IEEE Computer Society, 18(2):3--18, 1995.

....warehousing, nested databases, partitioned normal form, incremental computation. Materialized views are stored data collections that are derived from source data. Materialized views have attracted a signi cant amount of attention in recent years because of their importance in data warehousing [5, 7, 19]. In using materialized views, an issue of fundamental signi cance is developing ecient methods for updating the materialized views in response to changes in the source data; a procedure referred to as view maintenance. To maintain a materialized view, one has in general a choice between ....

Ashish Gupta and Inderpal S. Mumick. Maintenance of materialized views: problems, techniques and applications. IEEE Data Engineering Bulletin, special issues on materialized views and data warehousing, 18(2), 1996.

....persistent caches, which store method results in relations so that they can be reused across multiple queries over a period of time. Graefe provides an annotated bibliography of these ideas in Section 12.1 of his query processing survey [Gra93] Persistent caches are akin to materialized views [GM95] or function indices [MS86, LS88] from the point of view of a single query, they represent precomputed methods, rather than caches which are generated and used on the fly. Persistent caches are used in a way that is analogous to techniques for avoiding recomputation of common relational ....

A. Guptaand I.S. Mumick. Maintenance of materialized views: Problems, techniques, and applications. IEEE Data Engineering Bulletin, Special Issue on Materialized Views and Data Warehousing, 18(2):3--18, June 1995.

....labeled on multiple leaves of an operator tree, an update to the relation produces simultaneous multiple updates to multiple leaves of the operator tree. Such an example is given in Figure 3 (b) The update to r produces updates to two leaves of the tree. In this case, as Gupta and Mumick did in [8], we take one of these simultaneous updates each time and take it as an independent update to a leaf. In our example, we apply r to node 5 and conduct the propagation. We then apply r to node 6 and conduct the propagation. The performance of our algorithm can be improved by materializing ....

Ashish Gupta and Inderpal S. Mumick. Maintenance of materialized views: problems, techniques and applications. IEEE Data Engineering Bulletin, special issues on materialized views and data warehousing, 18(2), 1996.

....of consistency levels that are useful in the context of warehousing. Many incremental view maintenance algorithms have been developed for centralized database systems [BLT86, GMS93, CW91, HD92, QW91, SI84, CGL ] and a good overview of materialized views and their maintenance can be found in [GM95] Most of these solutions assume that a single system controls all of the base relations and understands the views and hence can intelligently monitor activities and compute all of the information that is needed for updating the views. As we showed in Example 1, when a centralized algorithm is ....

....tuple. However, for consistency and performance, the delete and the insert should be handled at the same time. Our algorithms can be easily extended for this type of processing, but we do not do it here. Further discussion of how to treat a modification as an insert and a delete may be found in [GM95] 5.2 Strobe The Strobe algorithm processes updates as they arrive, sending queries to the sources when necessary. However, the updates are not performed immediately on the materialized view MV ; instead, we generate a list of actions AL to be performed on the view. We update MV only when we ....

A. Gupta and I.S. Mumick. Maintenance of materialized views: Problems, techniques, and applications. IEEE Data Engineering Bulletin, Special Issue on Materialized Views and Data Warehousing, 18(2):3--18, June 1995.

....for frequency moments of a relation should preferably be done and updated as the records of the relation are inserted to the database. The general approach of maintaining views, such as distribution statistics, of the data has been well studied as the problem of incremental view maintenance (cf. [10]) Note that it is rather straightforward to maintain the (exact) frequency moments by maintaining a full histogram on the data, i.e. maintaining a counter m i for each data value i 2 f1; 2; ng, which requires memory of size Omega Gamma n) cf. 16] However, it is important that the ....

A. Gupta and I.S. Mumick, Maintenance of Materialized View: Problems, Techniques, and Applications, IEEE Data Engineering Bulletin, Special Issue on Materialized Views and Data Warehousing, 18(2), (1995).

....changes to hierarchically structured information. Detecting changes to data (henceforth referred to as deltas) is a basic function of many important database facilities and applications, including active databases [WC95] data warehousing [HGMW 95, IK93, ZGMHW95] view maintenance [GM95] and version and configuration management [HKG 94] As one example, consider the world wide web. A user may visit certain (HTML) documents repeatedly and is interested in knowing how each document has changed since the last visit. Assuming we have saved the old version of the document (which ....

....Information. Our focus is on hierarchical information, not flat information (e.g. files containing records or relations containing tuples) With flat information deltas may be represented simply as sets of tuples or records inserted into, deleted from, and updated in relations [GHJ 93, LGM95] In hierarchical information, we want to identify changes not just to the nodes in the data, but also to their relationships. For example, if a node (and its children) is moved from one location to another, we would like this to be represented as a move operation in the delta. ffl Object ....

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A. Gupta and I.S. Mumick. Maintenance of materialized views: Problems, techniques, and applications. IEEE Data Engineering Bulletin, Special Issue on Materialized Views and Data Warehousing, 18(2):3-- 18, June 1995.

....2 Related Work There has been a great deal of work in view maintenance and related problems in data warehousing, but to the best of our knowledge the lineage problem has not been addressed. Overviews of research directions and results in data warehousing can be found in [CD97, Wid95, WB97] [GM95] specifically covers view maintenance problems in data warehousing. Incremental view maintenance algorithms have been presented for relational algebra views [QW91] for aggregation [Qua96] and for recursive views [GMS93] View self maintainability issues are addressed in [QGMW96] Warehouse ....

A. Gupta and I. S. Mumick. Maintenance of materialized views: Problems, techniques, and applications. IEEE Data Engineering Bulletin, Special Issue on Materialized View and Data Warehousing, 18(2):3--19, June 1995.

....materialized views (Section 4) The algorithm takes as input a view definition and a sequence of updates to the base data, and propagates the changes to the copied data, querying the base data when necessary. 1. 1 Related Work Our work is based on previous work on materialized view maintenance [7], object technology [5] querying object oriented database [6, 9, 10] and semistructured data models [16, 13] In the rest of this subsection we specifically compare our GSDB views to relational views and object views defined using object classes. Most of the incremental view maintenance work ....

....object oriented database [6, 9, 10] and semistructured data models [16, 13] In the rest of this subsection we specifically compare our GSDB views to relational views and object views defined using object classes. Most of the incremental view maintenance work focuses on the relational model(see [7] for references) GSDB views are different from relation views in at least three major ways: 1) As mentioned earlier, in a GSDB view there is no schema to constrain changes to a particular region; with relational views, on the other hand, changes to a relation only impact views that refer to ....

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A. Gupta and I. Mumick. Maintenance of materialized views: Problems, techniques, and applications. IEEE Data Engineering Bulletin, Special Issue on Materialized Views and Data Warehousing, 18(2):3--18, June 1995.

....state, a global clock, timestamps, or transaction isolation properties. However, most of these definitions can be adapted to obtain the levels of consistency we define in the next section for single views. There are many view maintenance algorithms, both centralized and distributed [BLT86, GM95, GL95, SJ96] In our system, each view manager may implement any of these existing algorithms. The merge process only needs to know the consistency level provided by each view manager so that it can run the proper merge algorithm. Finally, in a multi database system [BGMS92, LMR90] updating the ....

A. Gupta and I.S. Mumick. Maintenance of materialized views: Problems, techniques, and applications. IEEE Data Engineering Bulletin, Special Issue on Materialized Views and Data Warehousing, 18(2):3--18, June 1995.

....(s) P oss(a; s) oe P (do(a; s) oe 8s(S 0 s oe P (s) 7 View Maintenance Supported by SSAs We could materialize the views by keeping extensional physical tables containing the entries that satisfy the view definitions. View maintenance is the problem of updating such a materialized views [GS1]. From our derived specification of the evolution of a database view V in terms of a aeSSA of the form (26) we can produce an algorithm for the automated maintenance of V . First we start with a materialization of the view at the initial state, that is, using the view definition and the initial ....

....updating the base tables, rather than to the changes in the base tables. Actually, changes in the base tables are not considered, but only the transactions, the base tables, and the view itself at the previous (execution) state. In that sense this is not an incremental view maintenance algorithm [GS1]. 7.1 An Example from Relational Algebra We will illustrate with an example from relational algebra how to apply the results obtained in section 5 to the generation of procedures for view maintenance. It is possible to rewrite every relational expression using first order logic. Actually, it can ....

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Gupta, A., Singh Mumick, I.: Maintenance of materialized views: Problems, techniques, and applications. IEEE-CS Data Engineering Bulletin 18 (1995) 3--18. Special issue on materialized views and data warehousing.

....helped verify the correctness of the system implementation and served as a guide for our performance experiments. 2 Related Work Overviews of data warehousing research and technologies can be found in [LW95, SC97] Basic incremental view maintenance algorithms are described in [BLT86, GMS93, GM95, GL95] Reference [Han87] discusses performance tradeoffs for materialized views in a conventional DBMS. The algorithms implemented in WHIPS are developed in [ZGMHW95, ZGMW96] they handle distributed autonomous data sources and continuously interleaving updates, and provide view consistency. In ....

A. Gupta and I.S. Mumick. Maintenance of materialized views: Problems, techniques, and applications. IEEE Data Engineering Bulletin, Special Issue on Materialized Views and Data Warehousing, 18(2):3--18, June 1995.

....on the database state, a global clock, timestamps, or transaction isolation properties. However, most of these definitions can be adapted to obtain the levels of consistency we define in the next section for single views. There are many view maintenance algorithms, both centralized and distributed [1, 5, 3, 13]. In our system, each view manager may implement any of these existing algorithms. The merge process only needs to know the consistency level provided by each view manager so that it can run the proper merge algorithm. Finally, in a multi database system [2, 9] updating the global view is ....

A. Gupta and I. Mumick. Maintenance of materialized views: Problems, techniques, and applications. IEEE Data Engineering Bulletin, Special Issue on Materialized Views and Data Warehousing, 18(2):3--18, June 1995.

....persistent caches, which store method results in relations so that they can be reused across multiple queries over a period of time. Graefe provides an annotated bibliography of these ideas in Section 12.1 of his query processing survey [Gra93] Persistent caches are akin to materialized views [GM95] or function indices [MS86, LS88] from the point of view of a single query, they represent precomputed methods, rather than caches which are generated and used on the fly. Persistent caches are used in a way that is analogous to techniques for avoiding recomputation of common relational ....

A. Gupta and I.S. Mumick. Maintenance of materialized views: Problems, techniques, and applications. IEEE Data Engineering Bulletin, Special Issue on Materialized Views and Data Warehousing, 18(2):3--18, June 1995.

....view. A disadvantage is that it is difficult to keep the view consistent as the underlying source changes. While it is possible to only partially materialize a view, for simplicity, we only consider the problems associated with full materialization here. We focus on incremental view maintenance [GM95] instead of view recomputation. We also ignore the issue of updates through views. View maintenance in a graph based data model such as OEM is fundamentally more difficult than in the relational model. Because of data sharing, an update to a source object reached via some path may affect a view ....

A. Gupta and I.S. Mumick. Maintenance of materialized views: Problems, techniques, and applications. IEEE Data Engineering Bulletin, Special Issue on Materialized Views and Data Warehousing, 18(2):3--18, June 1995.

....typical warehouse [WGL 96] The information stored at the warehouse is in the form of views, referred to as materialized views, derived from the data in the sources. In order to keep a materialized view consistent with the data at sources, the view has to be incrementally maintained [ZGMHW95, GM95] This maintenance of views incurs what is known as view maintenance or update costs. In this paper, we concentrate on the problem of selecting an appropriate set of materialized views, one of the most important design decisions in designing a data warehouse. Given some storage space constraint, ....

A. Gupta and I.S. Mumick. Maintenance of materialized views: Problems, techniques, and applications. IEEE Data Eng. Bulletin, Special Issue on Materialized Views and Data Warehousing, 18(2):3--18, 1995.

....efficient and simple algebraic expressions for maintenance of view expressions involving outerjoin operators. Outerjoin is supported in SQL. Further, outerjoins have recently gained importance because data from multiple distributed databases can be integrated by means of outerjoin views [GJM96, GM95, RU96] Outerjoins are also extensively used in object relational systems [BW89, BW90, BPP 93] Definition 3 (Outerjoin change table) A change table for a view involving outerjoin operators is defined as an outerjoin change table if the change table was either generated at an outerjoin ....

A. Gupta and I. Mumick. Maintenance of materialized views: Problems, techniques, and applica tions. Special Issue on Materialized Views and Data Warehousing, IEEE Data Engineering Bulletin, 18(2):3--19, June 1995.

....query from scratch. In this sense a materialized view is like a cache a commonly used version of the data that can be accessed quickly. Materialized views are finding applications in domains such as data warehousing, mobile systems, data visualization, banking, billing, and network management [9, 15] where quick response to complex queries is critical. Importance of Deferred View Maintenance: Like a cache, a materialized view gets out of date whenever the underlying base relations are modified. The process of making a materialized view consistent with the base relations from which it is ....

....views. There is an edge from a node N 1 to a node N 2 if N 1 derives view N 2 . Algorithms that compute changes to a view in response to changes to the base relations are called incremental view maintenance algorithms. A classification and survey of several view maintenance algorithms appears in [9]. View maintenance algorithms assume that the changes to the base relations are stored in one or more delta relations. In this paper, we will make the assumption that for every base relation R used in a view V , we have available a delta relation DeltaR(V ) containing all modifications ....

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A. Gupta and I. S. Mumick. Maintenance of Materialized Views: Problems, Techniques, and Applications. IEEE Data Engineering Bulletin, Special Issue on Materialized Views and Data Warehousing, 18(2):3--19, June 1995.

....the top of the figure. These views stored at the warehouse are often referred to as materialized views. The integerator, which lies in between the sources and the warehouse, is responsible for maintaining the materialized views at the warehouse in response to changes at the sources [ZGMHW95, CW91, GM95] This incremental maintenance of views incurs what is known as maintenance cost. We use the term maintenance cost interchangeably with maintenance time. Supported by NSF grant IRI 96 31952. One of the advantages of such a system is that user queries can be answered using the information ....

A. Gupta and I.S. Mumick. Maintenance of materialized views: Problems, techniques, and applications. IEEE Data Eng. Bulletin, Special Issue on Materialized Views and Data Warehousing, 18(2), 1995.

....views with multiset semantics, views with grouping aggregation, and recursive views; for various types of updates, e.g. insertions, deletions, modifications, to the database relations; and for modifications to the view definition itself. For a recent survey of the view maintenance literature, see [10]. The problem of what additional views to materialize, in order to reduce the cost of view maintenance, has been studied in the context of rule based systems based on the RETE, TREAT and A TREAT models [23, 13] These models are based on discrimination networks for each rule (view) the RETE model ....

....by a simple extension of the above scheme. Similar techniques apply for other operations, such as selection, projection, aggregation, duplicate elimination, union, intersection, difference, etc. The exact way to generate the queries and to compute the updates can be rather subtle; see for example [8, 10, 12]. This issue will be addressed in more detail in the full version of this paper. Consider now an expression tree. Given updates to the database relations at the leaves of the tree, the update to the result of an expression tree can be computed by starting from the updated database relations and ....

A. Gupta and I. S. Mumick. Maintenance of materialized views: Problems, techniques and applications. IEEE Data Engineering Bulletin, 18(2), June 1995. Special Issue on Materialized Views and Data Warehousing.

....base data, from which the warehouse views can be derived. In this paper, we only concentrate on the second issue, and assume that the relations of member databases are already obtained. Current research on materialized views is mainly focusing on the techniques for their processing and maintenance [11]. However the methodologies for materialized view design, such as how to determine the set of materialized views based on applications, is merely discussed. The framework presented in this paper highlights some issues in materialized view design in a distributed data warehouse environment. The ....

A. Gupta and I.S. Mumick. Maintenance of materialized views: problem, techniques, and applications. IEEE Data Engineering Bulletin, Special Issue on Materialized Views and Data Warehousing, 18(2):3--18, June 1995.

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A. Gupta and I. S. Mumick. Maintenance of materialized views: Problems, techniques and applications. IEEE Data Engineering Bulletin, 18(2), June 1995. Special Issue on Materialized Views and Data Warehousing.

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A. Gupta and I. S. Mumick. Maintenance of Materialized Views: Problems, Techniques, and Applications. IEEE Data Engineering Bulletin, Special Issue on Materialized Views and Data Warehousing, 18(2):3--19, June 1995.

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GUPTA, A., AND MUMICK, I. S. Maintenance of materialized views: Problems, techniques, and applications. IEEE Data Engineering Bulletin (Special issue on Materialized Views and Data Warehousing), June 1995, pg. 3-18.

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