1 / 8

RUM Conjecture of Database Access Method

RUM Conjecture of Database Access Method. Database Access Method. Defines how to store and access data in a database system Heap file Sorted file B+ Tree index Hash Index …. Requirements of A Good Access Method. Read optimized how much time it cost to read the data

mnorma
Download Presentation

RUM Conjecture of Database Access Method

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  1. RUMConjectureofDatabaseAccessMethod

  2. DatabaseAccessMethod • Defineshowtostoreandaccessdatainadatabasesystem • Heapfile • Sortedfile • B+Treeindex • HashIndex • …

  3. RequirementsofAGoodAccessMethod • Readoptimized • howmuchtimeitcosttoreadthedata • e.g.,rangesearch,equalitysearch • Updateoptimized • howmuchtimeitcosttoupdatethedata • e.g.,insert,delete,update • Memory(Space)optimized • howmuchspaceitusestostorethedata • e.g.,auxiliarystructures,duplicates

  4. However… RUMConjecture • RUMConjecture:Anaccessmethodthatcanminimizetwooutoftheread,update,andmemoryoverheads,cannotoptimizethethirdoverhead! • Inotherwords,theremightnotbethe“best”accessmethodthatisoptimalforallthethreerequirements!

  5. Example:Append-OnlyLog • Readunoptimized • Asearchmayneedtoscantheentirelog • Spaceunoptimized • Whendelete/updateanentry,oldentryisnotdeletedin-place • Updateoptimized • Eachupdatesimplyappendtheentrytothelog

  6. Example:B+Tree • Readoptimized: • EachsearchonlyvisitslogB(N)pages • Updateunoptimized: • AnupdaterequiresvisitingatleastlogB(N)pages • Spaceunoptimized: • Pagesoftenarenotfull

  7. Example:HashIndex • Readoptimized: • AquerysimplychecksO(1)bucket • Updateunoptimized: • Anupdatemayneedtosplitoverflowbuckets • Spaceunoptimized: • Bucketsoftenarenotfull

  8. OtherAccessMethods

More Related