PostgresDB 40P01: Deadlock Detected

Deadlock detected among transactions.
  1. Identify the queries involved in the deadlock:
    • Run the query: SELECT * FROM pg_catalog.pg_locks l JOIN pg_catalog.pg_stat_activity a ON l.pid = a.pid WHERE NOT GRANTED;This will help identify which queries are waiting for locks, potentially leading to a deadlock.
  2. Check for long-running queries that might be causing the deadlock:
    • Run the query: SELECT pid, age(clock_timestamp(), query_start), usename, query FROM pg_stat_activity WHERE state != 'idle' AND query NOT ILIKE '%pg_stat_activity%' ORDER BY query_start desc;This will show you any long-running queries that might need to be terminated to resolve the deadlock.
  3. Terminate the offending query if necessary:
    • Use the command: SELECT pg_cancel_backend(pid); or SELECT pg_terminate_backend(pid); replacing pid with the process ID of the query to be canceled or terminated.
  4. After resolving the deadlock, check for locks that might still be held:
    • Run the query: SELECT * FROM pg_locks WHERE NOT granted;This will show you if there are any remaining locks that were not automatically released.
  5. Analyze logs for the deadlock report:
    • Review the PostgreSQL log files for entries related to the deadlock, typically found in the log directory of your PostgreSQL installation. Look for entries around the time the deadlock occurred to get more insights into what caused it.
  6. Optimize queries:
    • Based on the information gathered from the logs and the queries involved in the deadlock, consider optimizing or rewriting the queries to prevent future deadlocks. This may involve adding indexes, reducing transaction sizes, or adjusting the order of operations in transactions.

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