PostgreSQL ERROR: deadlock detected — What It Means and How to Fix It
If you’ve ever seen the error "ERROR: deadlock detected" in PostgreSQL, chances are your application suddenly failed in production. This error is confusing, hard to reproduce, and often misunderstood. In this article, we’ll explain what it really means and how to fix it properly. What Is a Deadlock? A deadlock happens when two (or more) transactions block each other forever. Each transaction holds a lock and waits for another lock that will never be released. Simple Example Transaction A locks row 1 and waits for row 2 Transaction B locks row 2 and waits for row 1 PostgreSQL detects this situation and aborts one transaction to prevent an infinite wait. The Exact Error Message ERROR: deadlock detected DETAIL: Process 12345 waits for ShareLock on transaction 67890; blocked by process 54321. This means PostgreSQL killed one transaction to resolve the deadlock. Why Deadlocks Happen in PostgreSQL 1. Different Order of Updates The most common cause ...