Encyclopedia of Database Systems

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

Stop-&-Go Operator

  • Nikos HardavellasEmail author
  • Ippokratis Pandis
Reference work entry
DOI: https://doi.org/10.1007/978-1-4614-8265-9_1558


Non-pipelineable operator


A Stop-&-Go operator, or non-pipelineable operator, is a relational operator which cannot produce any result tuples unless it has consumed all of its input. A typical Stop-&-Go operator is the Sort operator. The usage of Stop-&-Go operators in the query execution plan limits the degree of operator-level parallelism.

Key Points

Some relational operators need to consume their entire input before they are able to produce tuples. These operators are called Stop-&-Go or non-pipelineable operators. A typical example of a Stop-&-Go operator is the Sort operator. To sort a set of tuples, the entire input set needs to be consumed before the operator can output the tuples in sorted order. There are many Stop-&-Go operators, such as various flavors of Join and Aggregation. For example, Hash Join is a Stop-&-Go operator because the Probe phase cannot start unless the Build phase has finished. Similarly, Sort-Merge Join is a Stop-&-Go operator because...

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Recommended Reading

  1. 1.
    Graefe G. Encapsulation of parallelism in the volcano query processing system. In: Proceedings of the ACM SIGMOD Conference on Management of Data; 1990. p. 102–11.Google Scholar
  2. 2.
    Johnson R, Hardavellas N, Pandis I, Mancheril N, Harizopoulos S, Sabirli K, Ailamaki A, Falsafi B. To share or not to share? In: Proceedings of the 33rd International Conference on Very Large Data Bases; 2007. p. 351–62.Google Scholar

Copyright information

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

Authors and Affiliations

  1. 1.Carnegie Mellon UniversityPittsburghUSA
  2. 2.Amazon Web ServicesSeattleUSA

Section editors and affiliations

  • Anastasia Ailamaki
    • 1
  1. 1.Informatique et CommunicationsEcole Polytechnique Fédérale de LausanneLausanneSwitzerland