Of Distributed Database Systems Exercise Solutions !new! - Principles

Principles of Distributed Database Systems — Exercise Solutions (Concise Guide)

Step 2 – Compute total cost (transmission):

Option 1: (R1 ⨝ S2) then with T3

Elara frowned. "But we need consistency, Silas. We can't have one customer getting their pancakes while another is told they're out of stock when they're not." It must abort one transaction (victim) to break the lock

Resolution:

The system detects the cycle. It must abort one transaction (victim) to break the lock. Typically, the youngest transaction or the one with the least work done is chosen (e.g., abort $T_3$). Join F2 with F1 → size=500 1000 0

Mastering the Core: Principles of Distributed Database Systems Exercise Solutions then with F1: cost 500 +10

Answer (in brief):

Smallest relation is F2 (500). Join F2 with F1 → size=500 1000 0.01=5000. Then join with F3 → total cost: move F2 to F1(500) + move 5000 to F3(5000) =5500. Better: Join F2 with F3 first: 500 2000 0.01=10,000; then with F1: cost 500 +10,000=10,500. Best: Move smallest (F2) to any site first, then join with the next smallest intermediate.