51a: Database Race Conditions

• Dirty writes: It happens when a transaction overwrites the value that is written by another transaction that hasn’t been committed yet.
• Dirty reads: A transaction reads a value from a write transaction that is not committed yet.
• Fuzzy Read: It happens when a transaction sees two different results when reading a value twice. When the difference is caused by committing another transaction, the value comes from pre-commit and after-commit.
• Phantom Read: It happens when a transaction reads a set of objects whiles another transaction changes some of the data; thus, it affects the result of the read.

• Related Note(s):
  • 55: Database Partitioning (Sharding);
  • Understanding How Database Transactions Work;
• Source(s):
  • Understanding Distributed Systems;
  • Software World #24: Understanding Distributed Systems with Roberto Vitillo

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