Parallel Evaluation of Multi-join Queries

A number of execution strategies for parallel evaluation of multi-join queries have been proposed in the literature. In this paper we give a comparative performance evaluation of four execution strategies by implementing all of them on the same parallel database system, PRISMA/DB. Experiments have been done up to 80 processors. These strategies, coming from the literature, are named: Sequential Parallel, Synchronous Execution, Segmented Right-Deep, and Full Parallel. Based on the experiments clear guidelines are given when to use which strategy. This is an extended abstract; the full paper appeared in Proc. ACM SIGMOD'94, Minneapolis, Minnesota, May 24–27, 199

Dataflow query execution in a parallel main-memory environment

The performance and characteristics of the execution of various join-trees on a parallel DBMS are studied. The results are a step in the direction of the design of a query optimization strategy that is fit for parallel execution of complex queries. Among others, synchronization issues are identified to limit the performance gain from parallelism. A new hash-join algorithm, called pipelining hash-join is introduced that has fewer synchronization constraints than the known hash-join algorithms. Also, the behavior of individual join operations in a join-tree is studied in a simulation experiment. The results show that the pipelining hash-join algorithm yields a better performance for multi-join queries. Also, the format of the optimal join-tree appears to depend on the size of the operands of the join. The results from the simulation study are confirmed with an analytic model for dataflow query executio

On the integration of IR and databases

Abstract: Integration of information retrieval (IR) in database management systems (DBMSs) has proven difficult. Previous attempts to integration suffered from inherent performance problems, or lacked desirable separation between logical and physical data models. To overcome these problems, we discuss a database approach based on structural object-orientation. We implement IR techniques using extensions in an object algebra called MOA. MOA has been implemented on top of the database backend Monet, a state-of-the-art highperformance database kernel with a binary relational interface. Our prototype implementation of the inference network retrieval model using MOA and Monet demonstrates the feasibility of this approach. We conclude with a discussion of the advantages of our database design

A Model for Pipelined Query Execution.

This paper develops an analytical model for pipelined execution of complex queries. The goal of this research is gaining insight in potential performance gain from the concurrent execution of pipelined relational operations. First, the model is developed in general terms, and after that it is elaborated for selection, unique, and join operations. Finally, it is shown how the model is used to understand the behavior of multi-operation queries. It is shown, how the individual characteristics of operations influence their cooperation in a pipeline. The model increases the understanding of dataflow query execution and can form a basis to generate query optimization heuristics for a parallel DBMS. 1 Introduction During the last years much attention has been paid to the development of parallel DBMSs. Teradata [Ter83], GAMMA [DGS90], Bubba [BAC90], HC16-186 [BrG89] and PRISMA/DB [Ame91,ABF92, WFA92] are examples of parallel DBMSs that actually were implemented. Each of these systems exploits..

Parallel Query Execution in PRISMA/DB.

this paper, the possibilities for parallelism in the execution of nested queries on PRISMA/DB are studied. In this study, both the algorithms for individual operations and the order in which operations are executed are taken into account. This paper is organized as follows: The remainder of this introduction is about parallelism and it introduces prisma. Section 2 describes query execution on prisma/db and derives a model for this execution. The possibilities for parallelism are identified. Section 3 is on algorithms for individual operations, their behavior in a parallel environment and it introduces pipelining algorithms. Join algorithms are used as an example in this section and the next one. Section 4 studies the implications of the results found in section 3, for query optimization. Section 5 concludes and summarizes the paper

Parallelism in a Main-Memory DBMS: The performance of PRISMA/DB

This paper evaluates the performance of the parallel, main-memory DBMS, PRISMA/DB. First, an abstract architecture for parallel query execution is presented. A performance model for the execution of simple relational operations on this architecture is developed. The parameters in the model are set using experiments on PRISMA/DB and the performance of PRISMA/DB is analized in the context of the model. Several conclusions can be drawn from the model combined with the results of the performance experiments. Firstly, the performance of PRISMA/DB appears to be competitive with respect to other systems. Secondly, the developed model can explain the results from the performance experiments to a large extent. Also, it is concluded that observed linear speedup for small numbers of processors cannot always be extrapolated to larger numbers of processors. Finally, it is concluded that the optimal number of processors for the parallel execution of an operation is smaller for a main-memory system t..

Road Collapse in Magnum

This paper describes the implementation of a triangulation based collapse algorithm in the general-purpose object oriented DBMS Magnum. The contribution of the paper is twofold. First, we show that true integration of complex spatial functionality in a DBMS can be achieved. Second, we worked out a collapse algorithm to be used in the complex area of map generalization

Implementing PRISMA/DB in an OOPL

PRISMA/DB is implemented in a parallel object-oriented language to gain insight in the usage of parallelism. This environment allows us to experiment with parallelism by simply changing the allocation of objects to the processors of the PRISMA machine. These objects are obtained by a strictly modular design of PRISMA/DB. Communication between the objects is required to cooperatively handle the various tasks, but it limits the potential for parallelism. From this approach, we hope to gain a better understanding of parallelism, which can be used to enhance the performance of PRISMA/DB. 1 Introduction The PRISMA project is a large scale research effort in which the development of a multi-computer and the implementation of non-trivial applications on top of this multicomputer are research issues. The project comprises the development of parallel hardware, the implementation of an operating system, the implementation of a parallel objectoriented language, and the implementation of applicat..