6.830: Lecture 8 (10/06/09)

This lecture will cover join algortihms, focusing in particular on Hash Join and Sort-Merge join and the relative tradeoffs of the two approaches.

Read the following paper:

• L.D. Shapiro. Join Processing in Database Systems with Large Main Memories. Red Book.

As you read, think about and come to class prepared to answer the following questions:

• Under what circumstances in Sort-Merge join preferable to hash?
• Both Hash Join and Sort Merge Join on unsorted inputs perform approximately same number of I/Os. So why does one sometimes outperform the other?
• Under what circumstances would index-nested loops join be preferable to hash or sort-merge join?

Last change: 10/04/09.