Postgres Playground

Playing with Postgres concurrency: locks, isolation levels, deadlock prevention.

• Transaction isolation

  • Read committed
  • Repeatable read

• Row-level locks

  • Implicit exclusive row-level lock (ordinary UPDATE)
  • Explicit shared row-level lock (SELECT FOR SHARE)
  • Explicit exclusive row-level lock (SELECT FOR UPDATE)

• Deadlocks

  • Deadlock on implicit exclusive row-level locks (ordinary UPDATE)
  • Deadlock on explicit exclusive row-level locks (SELECT FOR UPDATE)

• Deadlock prevention

  • Multiple transactions
  • Explicit global lock
  • Lock hierarchy