Reference Work Entry

Encyclopedia of Database Systems

pp 2030-2035

Parallel Query Execution Algorithms

  • Goetz GraefeAffiliated withHewlett-Packard Laboratories


Partitioned query execution; Partitioning


Parallel query execution algorithms employ multiple threads that together execute a single query execution plan, with the goal of increased processing bandwidth and decreased response time. Multiple forms of parallelism may be employed in isolation or in combination. Most parallel query execution algorithms are serial algorithms executed in multiple threads, usually with no or only minor adaptations to function correctly or efficiently in the multi-threaded environment.

Historical Background

Set-oriented query languages and the relational algebra have given rise to query optimization and parallel database processing almost from their beginning in the 1970s. They represented a new complexity or liability in database software design as non-procedural languages and physical data independence prevent users from specifying query processing steps and thus require an automatic system component to p ...

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