Encyclopedia of Database Systems

2018 Edition
| Editors: Ling Liu, M. Tamer Özsu

Parallel Hash Join, Parallel Merge Join, Parallel Nested Loops Join

  • Goetz GraefeEmail author
Reference work entry
DOI: https://doi.org/10.1007/978-1-4614-8265-9_1086


Parallel join algorithms


These join algorithms are parallel versions of the traditional serial join algorithms. They are designed to exploit multiple processors on a network, within a machine, or even within a single chip.

Key Points

Parallel join algorithms are based on the traditional serial join algorithms, namely (index) nested loops join, merge join, and (hybrid) hash join. The goal of parallel execution is to reduce the input sizes in each processing element, thus reducing the time for query completion even at the expense of increasing overall query execution effort due to data movement. Ideally, parallel join algorithms exhibit linear speed-up and linear scale-up.

Parallel join algorithms are orthogonal to pipelining among join operations in a complex query execution plan. Even a query with a single join can benefit from a parallel join algorithm. The essence of pipelining (and also of “bushy parallelism” in appropriate query execution plans) is to execute...

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Recommended Reading

  1. 1.
    Graefe G. Query evaluation techniques for large databases. ACM Comput Surv. 1993;25(2):73–170.CrossRefGoogle Scholar
  2. 2.
    Mishra P, Eich MH. Join processing in relational databases. ACM Comput Surv. 1992;24(1):63–113.CrossRefGoogle Scholar

Copyright information

© Springer Science+Business Media, LLC, part of Springer Nature 2018

Authors and Affiliations

  1. 1.Google, Inc.Mountain ViewUSA

Section editors and affiliations

  • Patrick Valduriez
    • 1
  1. 1.INRIALINANantesFrance