The official solution to 9.4 was a Paxos-based replacement for 2PC. But Paxos assumes a fair leader. She didn't have a leader. She had anarchy.
F1 = σ_Dept=‘Sales’(EMPLOYEE) F2 = σ_Dept=‘Eng’(EMPLOYEE) F3 = σ_Dept≠‘Sales’ ∧ Dept≠‘Eng’(EMPLOYEE) The official solution to 9
Exercises on deadlock detection typically provide a global wait-for graph or local graphs per site. She had anarchy
(using affinity matrices). The goal is to minimize irrelevant data access. Query Decomposition & Optimization: The goal is to minimize irrelevant data access
The problem was a phantom read. A classic edge case in multi-version concurrency control (MVCC). Node Alpha in London and Node Gamma in Tokyo had both approved a withdrawal from the same phantom account within 50 milliseconds of each other. Their local timestamps had conflicted, and the global consensus protocol—a modified Paxos—had chosen both. Now the ledger was in a superposition of states: both rich and poor.
Access to the official exercise solutions for " Principles of Distributed Database Systems
Profile update → eager replication (strong consistency). Like counter → lazy replication (eventual consistency).