Tuples In Relation Research Articles

Optimizing universal queries in relational databases

AbstractIn a relational database system based on the universal relation interface, users do not have to specify access paths when constructing universal queries. Moreover, users cannot control how to evaluate the queries efficiently (though they can construct usual queries, such as relational algebraic expressions, considering their processing costs). Thus, it is important for the system to evaluate given universal queries efficiently. This paper considers the representative instance of a database as a universal relation, and presents an optimization algorithm for evaluating a universal query for computing specified components of the tuples in the universal relation which satisfies a specified condition.

Factors affecting the performance of multiuser database management systems

While in the past 20 years database management systems (DBMS) have become a critical component of almost all organizations, their behavior in a multiuser environment has surprisingly not been studi...

Human performance in relational algebra, tuple calculus, and domain calculus

The results of two experiments are reviewed in which users' performance in developing query solutions using relational algebra, relational tuple calculus, and relational domain calculus was measured. Sample query solutions in domain and tuple calculus are analysed and compared for complexity. In terms of human factors, tuple calculus is apparently the weakest of the three languages, with domain calculus showing a decided improvement over tuple calculus. Query solution analysis indicates possible reasons for this result. Although users performed best in relational algebra, their performance in domain calculus was equal to that of relational algebra in three of four query classifications. Further investigation is needed to compare algebra and domain calculus in other query classifications, in order to more precisely determine their relative utility in solving complex queries.

A time bound on the materialization of some recursively defined views

A virtual relation (or view) can be defined with a recursive statement that is a function of one or more base relations. In general, the number of times such a statement must be applied in order to retrieve all the tuples in the virtual relation depends on the contents of the base relations involved in the definition. However, there exist statements for which there is an upper bound on the number of applications necessary to form the virtual relation, independent of the contents of the base relations. Considering a restricted class of recursive statements, we give necessary and sufficient conditions for statements in the class to have this bound.

A parallel pipelined relational query processor

This paper presents the design of a relational query processor. The query processor consists of only four processing PIPEs and a number of random-access memory modules. Each PIPE processes tuples of relations in a bit-serial, tuple-parallel manner for each of the primitive database operations which comprise a complex relational query. The design of the query processor meets three major objectives: the query processor must be manufacturable using existing and near-term LSI (VLSI) technology; it must support in a uniform manner both the numeric and nonnumeric processing requirements a high-level user interface like SQL presents; and it must support the query-processing strategy derived in the query optimizer to satisfy certain system-wide performance optimality criteria.

Validating database updates

Individual facts in the real world are represented by tuples in database relations (instances), while universal (time-independent) facts are treated as semantic constraints regarding database relation schemata. One important role of these semantic constraints is their use as integrity constraints that must not be violated by update operations. Among these, static constraints are represented by assertions, which are extended relational calculi in which every tuple variable is bound over a relation, and become true in a consistent database. When an update has been made on a consistent database, it is necessary to ascertain if the updated database is still consistent. It can be done by evaluating all the assertions in the updated database, but this is very time consuming. If a given assertion is in one of some classes, it is possible to devise an efficient validation procedure, which before the update is actually applied determines if the update violates the given assertion. In many cases a simplified form can be found, by examining whose value the properness of the given update is determined. The existence of such an efficient procedure and simplified form depends on what class the given assertion belongs, and also on what type of the update is to be made on what relation. This paper presents a method of finding such a procedure and simplified form using several simple syntactical transformation rules regarding extended relational calculi. This method is based on several basic properties in prepositional logic and many-sorted predicate logic.

A parallel pipelined relational query processor

This paper outlines the overall architecture of a query processor for relational queries and describes the design and control of its major processing modules. The query processor consists of only four processing modules and a number of random-access memory modules. Each processing module processes tuples of relations in a bit-serial, tuple-parallel manner for each of the primitive database operations which comprise a complex relational query. The query processor is designed to be manufacturable using existing VLSI technology, and to support in a uniform manner both the numeric and nonnumeric processing requirements a high-level query language like SQL presents.

Application of SQL/N to the attribute-relation associations implicit in functional dependencies

SQL/N is an expressive nonprocedural data base language that is upward compatible with SQL. Its expressive power is derived from both the use of natural quantifiers and the quantification of subsets of relations, in particular the subsets that are the groups of related tuples that occur in associations between relations. We show that SQL/N is also very expressive in specifying requests involving attribute-relation associations, and that attribute-relation associations are implicit in functional dependencies. We show that an attribute-relation association may be derived from the association between an algebraic projection relation and the relation on which the projection operation is performed. Two common cases of attribute-relation associations are investigated: first the case of an association restricted to a single relation, and second a more general attribute-relation association where an attribute from one relation is associated with a second relation.

Query optimization in star computer networks

Query processing is investigated for relational databases distributed over several computers organized in a star network. Minimal response-time processing strategies are presented for queries involving the select, project, and join commands. These strategies depend on system parameters such as communication costs and different machine processing speeds; database parameters such as relation cardinality and file size; and query parameters such as estimates of the size and number of tuples in the result relation. The optimal strategies specify relation preparation processes, the shipping strategy, serial or parallel processing, and, where applicable, the site of join filtering and merging. Strategies for optimizing select and join queries have been implemented and tested.