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Unformatted text preview: 3. Fetch ASG tuples as needed for each tuple in PROJ2 - 4. Ship whole ASG and PROJ2 to the third side. size (PROJ2)=2 and 1 tuple satisfies the condition size(ASG)= 8 and 2 tuples satisfy the condition Strategy 2 is not the best because the size of ASG is larger than the size of PROJ2. Also, the query doesn’t select any ASG attributes. Strategy 4 is the worst one because of the high communication expenses to ship both relations. This elimination leaves a choice between strategy 1 and 3. Since PROJ2 is not large, we pick strategy1. The optimization is: 1. Projection on PROJ2. Choose all tuples with PNO=”P4” 2. Move the result from step 1 to the site with ASG 3. Join with ASG 4. Select budget References Ozsu, M.T. & Valduriez, P. (1999). Principles of distributed database systems . New Jersey: Prentice Hall....
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- Spring '09
- Relational model, relation