Distributed DBMS - CS712 Power Point Slides Lecture 35

1 do the initial local processing 2 select the

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Unformatted text preview: es Databases • A non-commercial non-commercial database. database. • Based on the Hill Climbing Algorithm • No semijoins, No rep/frag • Cost of transferring the result to the user site from the final result site is not considered • Can minimize either total time or response time • Input include –Query Graph –Locations of relations –Relations’ statistics. 1- Do the initial local processing 2- Select the initial best plan (ES0) (ES –Calculate cost of moving all Calculate relations to a single site relations –Plan with the least cost is ES0 ES Plan 3- Split ES0 into ES1 and 3ES2 ES –ES1: Sending one of the Sending relation to other site, relations joined there relations –ES2:Sending the result :Sending back to site in ES0. back 4- Replace ES0 with ES1 and 4ES2 when we should have ES cost(ES1) + cost(local join) cost(local + cost (ES2) < cost (ES0) cost 5- Recursively apply step 3 5and 4 on ES1 and ES2, until no improvement until • Example • “Find the salaries of engineers Find working on CAD/CAM project” working • Involves EMP, PAY, PROJ and Involves ASG ASG ∀Πsal(PAY ⋈t...
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