W. Kim. On optimizing an SQL-like nested query. ACM Trans. on Database Systems, 7(3):443--469, Sep 82.  Home/Search   Document Not in Database   Summary   Related Articles   Check

....the query plan ahead of the user while waiting for the next DOM traversal step, we do not consider such speculative execution in this paper. 4 The Decorrelation Plan Space Decorrelation has been studied in the context of generating equivalent executions for correlated SQL queries in [6, 11, 15, 24]. In all previous work of which we are aware, plans are decorrelated when possible on the heuristic assumption that the decorrelated execution can be optimized better. On the contrary in ROLEX, when the navigation profile indicates that a node will seldom be visited, correlated execution may be ....

....query would also be parametrized by z, that is Q x (z) The decorrelated query Q x (z) can then be decorrelated further to eliminate the parameter z and thereby obtain Q yz x . Each of these decorrelated queries may be a candidate for further query transformations like those described in [15]. Since these transformations are standard in the literature on query processing, we do not present details here. 4.2 Multi Parameter Decorrelation The extension of the technique above to tag queries with multiple parameters is straightforward. Consider a tag query Q x (s 1 ; s 2 ; s k ....

W. Kim. On optimizing an SQL-like nested query. ACM Transactions on Database Systems, 7(3):443--469, Sept. 1982.

....the query plan ahead of the user while waiting for the next DOM traversal step, we do not consider such speculative execution in this paper. 4 The Decorrelation Plan Space Decorrelation has been studied in the context of generating equivalent executions for correlated SQL queries in [6, 11, 15, 24]. In all previous work of which we are aware, plans are decorrelated when possible on the heuristic assumption that the decorrelated execution can be optimized better. On the contrary in ROLEX, when the navigation profile indicates that a node will seldom be visited, correlated execution may be ....

....above decorrelated query would also be parametrized by , that is . The decorrelated query can then be decorrelated further to eliminate the parameter and thereby obtain . Each of these decorrelated queries may be a candidate for further query transformations like those described in [15]. Since these transformations are standard in the literature on query processing, we do not present details here. 4.2 Multi Parameter Decorrelation The extension of the technique above to tag queries with multiple parameters is straightforward. Consider a tag , ....

W. Kim. On optimizing an SQL-like nested query. ACM Transactions on Database Systems, 7(3):443--469, Sept. 1982.

....i.e. setorientation was mostly out of their scope. The database was queried in a navigational manner along the references defined between the database objects (e.g. path expressions in OPAL [33] By now a lot of research focuses on full fledged query languages for object oriented database models [22, 44]. Seen from a more general point of view the upcoming object oriented query languages exploit facilities to query along predefined relationships (in [6] called functional join) as well as to use traditional value based relational join capabilities. The functional join facility resembles the ....

W. Kim, On Optimizing an SQL-like Nested Query, in: ACM TODS 7 (1982) 443-469.

....in pipeline. Each node operator in a pipe starts execution as soon as the operator(s) producing its input have output enough data for it to start; until these data are produced, the consumer waits. The initial query tree is built by a preoptimizer, which performs unnesting of nested queries [14], transforms disjunctions into unions, and places selection nodes below join nodes on the same relations. Set operations are placed below the root projection and separated from the nodes containing predicates by further projections. So, projections, selections, and joins form PSJ subtrees, in ....

....than the square root of the processor s memory size, the hash algorithm of Shapiro [24] is used. Otherwise, projections are introduced to sort the input relations, and the merge join is used. The inner relation or hash table for classic joins is selected as the largest one fitting in memory [14]. The inner relation for semijoins is the one not retained in the output. The inner relation of an antijoin or outerjoin is determined by the operator s semantics [14] 2] and cannot be changed. For restrictions, we consider two algorithms, one used when the input relation comes sorted on the ....

[Article contains additional citation context not shown here]

W. Kim, "On Optimizing an SQL-Like Nested Query," ACM Trans. Database Systems, vol. 7, no. 3, pp. 443--469, 1982.

....queries to concrete evaluation algorithms. We are presenting a new XML algebra and a query optimization framework based on query normalization and query unnesting (also known as query decorrelation) There are many proposals on query optimization that are focused on unnesting nested queries [23, 18, 26, 11, 12, 9, 28]. Nested queries appear more often in XML queries than in relational queries, because most XML query languages, including XQuery, allow complex expressions at any point in a query. Current commercial database systems typically evaluate nested queries in a nested loop fashion, which is unacceptable ....

W. Kim. On Optimizing an SQL-like Nested Query. ACM Transactions on Database Systems, 7(3):443{ 469, September 1982.

.... been noted that the nested form is often easier for users to formulate and to understand [12] Existing research (on nested queries) has sought methods of reducing the evaluation costs, typically by transforming a nested query into a logically equivalent form that can be evaluated more efficiently [2, 3, 10]. However, the class of nested queries with aggregates is especially interesting. First, such queries are commonly encountered. For example, to list employees who are high earners where highearners are defined as a certain factor of the average salaries of employees, requires a nested query ....

....with an example to reiterate the motivation behind online aggregation, i.e. to provide fast response of (approximate) answers to users. Before that, we shall review the two types of nested queries with aggregates that are relevant to our work. 2. 1 Types of Nested Queries with Aggregates In [10], Kim presented a classification of nested query types, two of which involve aggregates in the inner query block. For illustration, we shall use the example of a large admissions database that records information on persons (of different nationalities) applying to graduate business schools. The ....

[Article contains additional citation context not shown here]

W. Kim. On optimizing an sql-like nested query. ACM Transactions on Database Systmes, 7(3), September 1982.

....rules to guide semantic reasoning makes our optimizer extensible in a manner that is complementary to the extensibility benefits of existing rule based technology. 1 Introduction Query optimizers are hard to build. In the past, relational optimizers have proved to be brittle and error prone [17]. The added complexity of objects and hence object queries makes the task of building object (i.e. object oriented and object relational) database optimizers that much more difficult. It is now accepted practice to use software engineering techniques when building optimizers. For example, many ....

W. Kim. On optimizing an SQL-like nested query. ACM Transactions on Database Systems, 7(3):443--469, September 1982.

....list is considered each time) Furthermore, a set of types belonging to the set SourceSchema, denoting all the types found in the data sources, are treated as source nodes of a graph. For the rest of the types, we can derive an SQL expression by using existing view reduction algorithms, such as [33] corrected with the results of [19, 44, 45] 14, 11, 41, 48, 36] Our algorithm is applicable to graphs of activities that do not involve updates. In most cases, an update operation can be considered as the combination of insertions and deletions or as the application of the appropriate function ....

Won Kim. On Optimizing an SQL-like Nested Query. ACM Trans. On Database Systems 7(3): 443-469 (1982)

....P Fig. 26. Application of Partial Evaluation Techniques to Agent Programs Another area of research that is very closely related to ours is query optimization in relational and deductive databases [Graefe 1995; Haas et al. 1989; Ioannidis and Kang 1990; Graefe 1993; Ibaraki and Kameda 1984; Kim 1982; Mumick et al. 1996] and in mediators [Adali et al. 1996; Levy et al. 1996a; Haas et al. 1997; Ambite Improving Performance of Heterogeneous Agents Delta 47 and Knoblock 2000; Duschka et al. 2000] It is worth noting that this list is not exhaustive since over the last decades, enormous effort ....

Kim, W. 1982. On optimizing an sql-like nested query. ACM Transactions on Database Systems 7, 3 (September), 443--469.

No context found.

W. Kim. On optimizing an SQL-like nested query. ACM Trans. on Database Systems, 7(3):443--469, Sep 82.

No context found.

W. Kim. On optimizing an SQL-like nested query. ACM Trans. on Database Systems, 7(3):443--469, Sep 82.

No context found.

W. Kim. On optimizing an SQL-like nested query. ACM Trans. on Database Systems, 7(3):443--469, Sep 82.

No context found.

Won Kim. On Optimizing an SQL-like Nested Query. ACM Trans. Database Syst., 7(3):443--469, 1982.

No context found.

W. Kim. On Optimizing an SQL-like Nested Query. In ACM Transactions on Database Systems, Vol 7, No.3, 1982.

No context found.

W. Kim. On optimizing an SQL-like nested query. ACM Trans. on Database Systems, 7(3):443--469, Sept. 1982.

No context found.

W. Kim. On Optimizing an SQL-like Nested Query. ACM Transactions on Database Systems, 7(3):443-- 469, September 1982.

No context found.

W. Kim. On optimizing an sql-like nested query. TODS, 7(3):443--469, 1982.

No context found.

W. Kim. On optimizing an SQL-like nested query. ACM Trans. on Database Systems, 7(3):443--469, Sep 82.

No context found.

W. Kim. On optimizing an SQL-like nested query. ACM Trans. on Database Systems, 7(3):443--469, Sep 82.

No context found.

W. Kim. On Optimizing an SQL-like Nested Query. ACM Transactions on Database Systems, 7(3):443-- 469, September 1982.

No context found.

W. Kim. On optimizing an SQL-like nested query. ACM Trans. on Database Systems, 7(3):443--469, Sep 82.

No context found.

W. Kim. On optimizing an SQL-like nested query. ACM Trans. on Database Systems, 7(3):443--469, Sep 82.

No context found.

W. Kim. On optimizing an SQL-like nested query. ACM Transactions on Database Systems, 7(3):443--434, September 1982.

No context found.

15 Won Kim. On Optimizing an SQL-like Nested Query. ACM Transactions on Database Systems, 7(3):443--469, September 1982.

No context found.

Kim, W., "On optimizing an SQL-like nested query," ACM Trans. on Database Systems 7(3), Sept., 1982, pp. 443--469.

First 50 documents  Next 50

Online articles have much greater impact   More about CiteSeer.IST   Add search form to your site   Submit documents   Feedback  

CiteSeer.IST - Copyright Penn State and NEC