Skip Navigation

The Computer Journal 1985 28(5):501-507; doi:10.1093/comjnl/28.5.501
© 1985 by British Computer Society
This Article
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Similar articles in this journal
Right arrow Similar articles in ISI Web of Science
Right arrow Alert me to new issues of the journal
Right arrow Add to My Personal Archive
Right arrow Download to citation manager
Right arrow Search for citing articles in:
ISI Web of Science (1)
Right arrowRequest Permissions
Google Scholar
Right arrow Articles by Gray, P. M. D.
Right arrow Articles by Esslemont, P.
Right arrow Search for Related Content
Social Bookmarking
Add to CiteULike   Add to Connotea   Add to Del.icio.us  
What's this?

The Performance of a Relational Interface to a Codasyl Database

P. M. D. Gray and P. Esslemont *

Department of Computing Science, University of Aberdeen, King's College, Old Aberdeen, AB9 3UB, UK

A program generator (ASTRID) has been built which generates Fortran code to access records stored in a Codasyl database which satisfy a query written in a generalised relational algebra. The Join operation can be done either by using coset pointers or else by sort-merge. Also projection and grouping operations will require sorts to find and remove duplicate values if they cannot be accessed in sorted order.

A novel method of combining grouping and sorting operations via a sparse array technique is presented. Comparisons are made between this method and separate sorting followed by grouping; timings are given to show the significant advantage in practice.

A number of programs have been generated and run using different access paths, with and without sorts. Comparisons between timings and monitored page charges are made and heuristics suggested for predicting the best method. These are shown to be different from those used by Selinger et al. for the System R relational database.


* Now at SCICON, Berners Street, London.

§ Department of Computing Science, University of Aberdeen, King's College, Old Aberdeen, AB9 3UB


Add to CiteULike CiteULike   Add to Connotea Connotea   Add to Del.icio.us Del.icio.us    What's this?




Disclaimer: Please note that abstracts for content published before 1996 were created through digital scanning and may therefore not exactly replicate the text of the original print issues. All efforts have been made to ensure accuracy, but the Publisher will not be held responsible for any remaining inaccuracies. If you require any further clarification, please contact our Customer Services Department.