Motivating Example

Misses several opportunities: selections could have been `pushed’ earlier, no use is made of any available indexes, etc.

Goal of optimization: To find more efficient plans that compute the same answer.

SELECT S.sname

FROM Reserves R, Sailors S

WHERE R.sid=S.sid AND

R.bid=100 AND S.ratingɱ

RA Tree:

Plan:

Cost: 500+500*1000 I/Os