Parallel database

<h2 id="types-of-parallelism">Types of parallelism</h2>
Intraquery parallelism
A single query that is executed in parallel using multiple processors or disks.<a class="footnote-ref" id="fnref:2" href="#fn:2"><sup>2</sup></a>
Independent parallelism
Execution of each operation individually in different processors only if they can be executed independent of each other. For example, if we need to join four tables, then two can be joined at one processor and the other two can be joined at another processor. Final join can be done later.
Pipe-lined parallelism
Execution of different operations in pipe-lined fashion. For example, if we need to join three tables, one processor may join two tables and send the result set records as and when they are produced to the other processor. In the other processor the third table can be joined with the incoming records and the final result can be produced.
Intraoperation parallelism
Execution of single complex or large operations in parallel in multiple processors. For example, ORDER BY clause of a query that tries to execute on millions of records can be parallelized on multiple processors.

<h2 id="references">References</h2>

<ol>
<li id="fn:1"><p>Dewitt, David; Gray, Jim (1992). "Parallel database systems: The future of high performance database systems" (PDF). Communications of the ACM. 35 (6): 85. CiteSeerX 10.1.1.119.8427. doi:10.1145/129888.129894. <a href="/wiki/David_DeWitt" target="_blank">/wiki/David_DeWitt</a> <a href="#fnref:1" class="footnote-back-ref">↩</a></p></li>
<li id="fn:2"><p>Kandasamy, Saravanakumar. "Parallel Database - Intraquery Parallelism - Advanced Database Management System". Blogger. Retrieved September 10, 2017. <a href="http://www.exploredatabase.com/2014/03/parallel-database-intraquery-parallelism.html" target="_blank">http://www.exploredatabase.com/2014/03/parallel-database-intraquery-parallelism.html</a> <a href="#fnref:2" class="footnote-back-ref">↩</a></p></li>
</ol>

Parallel database open-in-new

Parallel database