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You have a deadlock error in PostgreSQL caused by two transactions locking tables in different orders. Which fix will prevent the deadlock?

medium📝 Debug Q6 of 15
PostgreSQL - Transactions and Concurrency
You have a deadlock error in PostgreSQL caused by two transactions locking tables in different orders. Which fix will prevent the deadlock?
AIncrease statement_timeout to avoid aborts
BEnsure all transactions lock tables in the same order
CDisable autovacuum to reduce locking
DUse SERIALIZABLE isolation level always
Step-by-Step Solution
Solution:

  1. Step 1: Identify cause of deadlock

    Deadlocks often occur when transactions lock resources in different orders.

  2. Step 2: Apply prevention strategy

    Ensuring all transactions lock tables in the same order prevents cycles and deadlocks.

  3. Final Answer:

    Ensure all transactions lock tables in the same order -> Option B

  4. Quick Check:

    Consistent lock order = Deadlock prevention [OK]
Quick Trick: Lock tables in same order to avoid deadlocks [OK]
Common Mistakes:
  • Thinking increasing timeout fixes deadlocks
  • Disabling autovacuum affects performance, not deadlocks
  • Assuming SERIALIZABLE isolation prevents all deadlocks

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