Z. Xie and J. Han. Join index hierarchies for supporting efficient navigation in object-oriented databases. In Proc. Int. Conf. on Very Large Data Bases (VLDB), pages 522--533, 1994.  Home/Search   Document Not in Database   Summary   Related Articles   Check

.... devoted to their optimization: also in this case, the focus is on transforming pointer chasing operations which are considered rather expensive into joins of pointer sets stored in auxiliary access structures, such as class extents [24] access support relations [25] and join indices [38] [41]. Although it may seem that a similar approach may be extended to the Web, we show that the more involved nature of access paths in Web sites and the absence of ad hoc auxiliary structures introduces a number of subtleties. We compare two main approaches to query optimization: i) the first one, ....

Xie Z. and Han J. Join index hierarchies for supporting efficient navigations in object-oriented databases. In International Conf. on Very Large Data Bases (VLDB'94), Santiago, pages 522--533, 1994.

....join index must be built for each access path. Moreover, a join index is sensitive to key length, and is usually only used for a single join, not a whole path. Path navigation has been studied in object oriented (OO) databases. OO databases use sequences [4,22] or hierarchies of path indexes [32] to support long paths, requiring multiple index lookups per path. Our mechanism supports following paths with a single index lookup. Also, OO indexes support linear paths, requiring multiple indexes to evaluate branchy queries. Our structure provides a single index for all queries, and one ....

Z. Xie and J. Han. Join index hierarchies for supporting efficient navigations in object-oriented databases. In Proc. VLDB, 1994.

.... for estimating predicate selectivities, and for estimating the number of tuples one relation (or class) produces when joined with another relation (or class) Object oriented statistics can be somewhat more complicated if the class hierarchy is taken into account, e.g. CCY94, RK95, SS94, XH94] However, these statistics are not well suited for long sequences of joins as embodied in path expressions. A cost based optimizer for path expressions may, for example, need to accurately estimate the number of Book.Author.Address.City paths in the database. In Lore we set a threshold k, and ....

Z. Xie and J. Han. Join index hierarchies for supporting efficient navigations in object-oriented databases. In Proceedings of the Twentieth International Conference on Very Large Data Bases, pages 522--533, Santiago, Chile, September 1994. 21

....(g, 5.1) h, 2.2) i, 1.1) g, 5.1) e, 3.1) b, 1.2) f,4.2) d, 4.1) c, 2.1) a, 3.2) h, 2.2) i, 1.1) a 3.2 b 1.2 c 2.1 d 4.1 e 3.1 f 4.2 g 5.1 h 2.2 i 1.1 (a) B tree (b) Hash Table (c) Direct Mapping Fig. 2. Mapping techniques indices is reported in [BK89, KM90, XH94] A recent paper describes two new join algorithms that are based on join indices [LR99] Both algorithms store the join result in two files on disk, which need to be merged to obtain the actual join result. Therefore, their algorithms achieve their performance gains mostly in situations where ....

Xie Z, Han J (1994) Join index hierarchies for supporting efficient navigations in object- oriented databases. In: Proc. of the Conf. on Very Large Data Bases (VLDB), September 1994, Santiago, Chile, pp 522-- 533

.... are the object oriented model [Cat97] and the object relational data model [SM96] Several indexes dealing with special problems in these data models have been invented, e.g. nested indexes [BK89] path indexes [BK89] multi indexes [MS86] access support relations [KM92] join index hierarchies [XH94]. The predominant problem attacked by these index structures is the efficient evaluation of path expressions. However, the problem of indexing data items with set valued attributes is of no less importance. Consider for example the following queries: retrieve all students attending at least a ....

Z. Xie and J. Han. Join index hierarchies for supporting efficient navigation in object-oriented databases. In Proc. Int. Conf. on Very Large Data Bases (VLDB), pages 522--533, 1994.

....set valued predicates is few and far between. Several indexes dealing with special problems in the object oriented [7] and the objectrelational data models [23] have been invented, e.g. nested indexes [4] path indexes [4] multi indexes [21] access support relations [18] join index hierarchies [27]. The predominant problem attacked by these index structures is the efficient evaluation of path expressions. With the exception of signature files [16] and Russian Doll Trees [14] the problem of indexing data items with set valued attributes has been neglected by the database community. The ....

Z. Xie and J. Han. Join index hierarchies for supporting efficient navigation in objectoriented databases. In Proc. Int. Conf. on Very Large Data Bases (VLDB), pages 522--533, 1994. 21

.... devoted to their optimization: also in this case, the focus is on transforming pointer chasing operations which are considered rather expensive into joins of pointer sets stored in auxiliary access structures, such as class extents [17] access support relations [18] and join indices [29] [31]. Although it may seem that a similar approach may be extended to the Web, we show that the more involved nature of access paths in Web sites and the absence of ad hoc auxiliary structures introduces a number of subtleties. We compare two main approaches to query optimization: i) the first one, ....

Xie Z. and Han J. Join index hierarchies for supporting efficient navigations in object-oriented databases. In International Conf. on Very Large Data Bases (VLDB'94), Santiago, pages 522-- 533, 1994.

....The value of an attribute of an object is an object or a set of objects. The access scope of a query may include the nested attributes, which is essentially object accesses along references chains from one object instance to another. Methods for this support of nested predicates can be found in [20, 6, 13, 14, 24, 10, 11, 8]. b) For inheritance hierarchy: The access scope of a query against a class may include instances of the class and those of its subclasses. An index structure can support both instances in the same search index. Previous work includes [17, 1, 18, 19, 16, 22, 21] 2. Behavioral For OODB, queries ....

....is known as index interaction [9] Index interaction has a larger performance impact when the global effect of indexing multiple query paths is considered. Some work that deals with this effect includes [5, 13] Following the study of access support relation [13, 14] and join index hierarchies [24], a new indexing structure, called the triple node hierarchy is proposed in this paper. The triple node hierarchy supports object references by maintaining direct association between two objects along a path expression of arbitrary path length while the intermediate objects are Aggregation ....

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Z. Xie and J. Han. Join index hierarchies for supporting efficient navigations in objectoriented databases. In Proceeding of the 20th VLDB Conference Santiago, Chile, pages 522--533, 1994.

.... algorithms to support spatial joins have been developed [3, 14, 19, 26, 32] Another special join algorithm has been developed for joining objects on set valued attributes [18] Another important research area is the development of index structures that allow to accelerate the evaluation of joins [16, 22, 23, 31, 39, 40]. However, if there is no selection prior to a join or the selections exhibit a high selectivity value (i.e. many output tuples are produced) the performance gain of these algorithms is limited. This is also true for bitmap join indices [31] that were developed especially for Data Warehouse ....

Z. Xie and J. Han. Join index hierarchies for supporting efficient navigation in objectoriented databases. In Proc. Int. Conf. on Very Large Data Bases (VLDB), pages 522--533, 1994.

.... the sort merge and hash joins see [13, 14] A lot of effort has also been spent on parallelizing join algorithms based on sorting [10, 25, 26, 34] and hashing [6, 12, 36] Another important research area is the development of index structures that allow to accelerate the evaluation of joins [16, 22, 21, 29, 40, 42]. All of these algorithms concentrate on simple join predicates based on the comparison of two atomic values. Predominant is the work on equi joins, i.e. where the join predicate is based on the equality of atomic Permission to copy without fee all or part of this material is granted provided ....

Z. Xie and J. Han. Join index hierarchies for supporting efficient navigation in object-oriented databases. In Proc. Int. Conf. on Very Large Data Bases (VLDB), pages 522--533, 1994.

....is the efficient execution of updates. Whenever an update is performed, some of the precomputed joins become invalid and must, thus, be recomputed. Aggregation indexing techniques can therefore be classified based on whether they maintain some additional information to efficiently perform updates [4, 18] or not [6, 9] In the former case, no object accesses, except to the modified object, are needed to recompute the join and update the index. In the latter case, objects other than the modified object need to be accessed to recompute the join and update the index. The third group of techniques ....

Zh. Xie and J. Han. Join Index Hierarchies for Supporting Efficient Navigations in Object-Oriented Databases. In Proc. the 20th Int. Conf. on Very Large Data Bases, pages 522--533, Santiago, Chile, 1994.

.... of generalized join indices [Val87] BK89] was the first proposal for indexing path expressions, and the access support relations [KM90] are another systematic approach for materializing the functional join along arbitrarily long path expressions; it was later augmented to join index hierarchies [XH94] Many more proposals exist by now. SC90] were the first who systematically evaluated three pointer join techniques (naive, sorting, and hash partitioning) in comparison to a value based join. Their work was augmented by [DLM93] to parallel database systems. DLM93] also allowed nested sets of ....

Z. Xie and J. Han. Join index hierarchies for supporting efficient navigations in object-oriented databases. In Proc. of the VLDB Conf., pages 522--533, Santiago, Chile, September 1994.

.... preliminary version of Lore s query language, Lorel, was introduced in [QRS 95] Details of the current version of Lorel appear in [AQM 97] Needless to say, there has been a significant amount of work in indexing for object oriented databases, e.g. KKD89, SS94, RK95, KM92, CCY94, BG92, XH94] All of this work depends on the database having a fixed schema based on a known, strongly typed class hierarchy. In our environment we must take a different approach to indexing, since we do not have a fixed schema, and comparable objects may take on different types. Other related work includes ....

Z. Xie and J. Han. Join Index Hierarchies for Supporting Efficient Navigations in ObjectOriented Databases. In Proceedings of the Twentieth International Conference on Very Large Databases, pages 522--533, Santiago, Chile, September 1994.

....in a knowledge base and the frequency of updates. In fact, our results show that in the presence of time indices consisting of paths of join indices offer a better option [Top93] The advantages of join indices for supporting efficient navigation in object oriented databases are also shown in [XH94] where the concept of join index hierarchies is introduced. As for future work, there are many interesting directions to pursue, including: Extending the cost model so it is capable of handling wider range of queries such as recursive queries. A second direction is exploring techniques such as ....

Z. Xie and J. Han. Join index hierarchies for supporting efficient navigations in object-oriented databases. In Proceedings of the 20th VLDB Conference, pages 522--533, 1994.

....input relations are much larger than main memory. Join indices have been used in [23] to define a graph between pages in two relations based on whether the pages contain a pair of matching records. This graph is then used to help in parallelizing the join. Hierarchies of join indices are used in [32] to speed up navigation in object oriented databases. Join indices have also been used in spatial databases [26, 20] 11 Conclusions We have presented two new algorithms, called Jive join and Slam join, for performing joins given a join index. We have derived detailed analytic cost formulas for ....

Xie, Z., and Han, J. Join index hierarchies for supporting efficient navigations in object-oriented databases. In Proceedings of the 1994 VLDB conference (1994), pp. 522--533.

....techniques have the additional advantages of (1) being easily implementable and (2) resulting only in a neglectable increase in optimization time. 1 Introduction Since the introduction of OBMS, much work has been devoted to optimizing object queries. Special index structures for path indexes [2, 12, 18, 20], class indexes [17, 16] and function materialization [11] have been proposed. Logical optimization techniques have been developed. They cover path evaluation [1, 13] factorization [5] unnesting [6, 19] optimization in the presence of expensive methods [9, 15] disjunctions [14] or aggregates ....

....[14] or aggregates [7] Looking at all the effort, it is surprising, that, in the context of query optimization, class hierarchies did not receive special attention. The only special support developed so far are index structures that are capable to index multiple sets or classes in a hierarchy [17, 16, 20]. So far, no effort has been made to exploit class hierarchies to optimize queries that refer to classes integrated into a class hierarchy. The goal of the paper is to start investigations in this direction. Either because they are made available to the users or because of preliminary rewritings ....

Z. Xie and J. Han. Join index hierarchies for supporting efficient navigation in objectoriented databases. In Proc. Int. Conf. on Very Large Data Bases (VLDB), pages 522--533, 1994.

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Z. Xie and J. Han. Join index hierarchies for supporting efficient navigation in object-oriented databases. In Proc. Int. Conf. on Very Large Data Bases (VLDB), pages 522--533, 1994.

No context found.

Z. Xie and J. Han. Join index hierarchies for supporting efficient navigations in object-oriented databases. In Proceedings of the International Conference on Very Large Data Bases, pages 522--533, 1994.

No context found.

Z. Xie and J. Han. Join index hierarchies for supporting efficient navigations in object-oriented databases. In Proceedings of the International Conference on Very Large Data Bases, pages 522--533, 1994.

No context found.

Z. Xie and J. Han. Join index hierarchies for supporting efficient navigations in object-oriented databases. In Proceedings of the International Conference on Very Large Data Bases, pages 522--533, 1994.

No context found.

Z. Xie and J. Han. Join index hierarchies for supporting efficient navigation in object-oriented databases. In Proc. Int. Conf. on Very Large Data Bases (VLDB), pages 522--533, 1994.

No context found.

Z.H. Xie and J.W. Han. Join Index Hierarchies for supporting efficient navigations in object-oriented databases, In Proceedings of 20th International Conference on Very Large Databases, 1994.

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