Encyclopedia of Database Systems

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

Index Join

  • Jingren Zhou
Reference work entry
DOI: https://doi.org/10.1007/978-1-4614-8265-9_870

Synonyms

Index join; Index loop join; Index nested loop join

Definition

The index join is a variant of the nested loop join in database systems using index. The join predicate can be either an equality predicate or a range predicate. The algorithm starts with reading the outer relation R. For each tuple RR, instead of scanning the entire inner relation S, an index on S is used to find matching tuples and add them to the result.

Key Points

An index on S is applicable for an index join if one join attribute is the leading indexed key of the index. If the join predicate is an equality predicate, an index lookup is performed for each outer tuple. If the join predicate is a range predicate, for each outer tuple, an index seek is performed to locate the first matching tuple, followed by an index scan for the rest matching tuples. Compared with the nested loop join, the index join saves disk I/Os for reading the entire inner relation S multiple times.

Cross-References

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Recommended Reading

  1. 1.
    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.Alibaba GroupHangzhouChina

Section editors and affiliations

  • Evaggelia Pitoura
    • 1
  1. 1.Department of Computer Science and EngineeringUniversity of IoanninaIoanninaGreece