How to diagnose and fix the 57014 query_canceled error code in Postgres.

The 57014 error code in PostgreSQL corresponds to a query_canceled event. This error occurs when a query is canceled by an explicit request, such as a user action, a database timeout parameter like statement_timeout, or if the system decides to cancel the query for some reason, such as during a shutdown or due to resource constraints.

To diagnose and fix a 57014 error, follow these steps:

  1. Identify the Cause: Determine what triggered the cancellation of the query. This could be a manual cancellation by a user, a configured timeout parameter, or a system-level interruption.
  2. Review Query Execution Time: Long-running queries are often the reason for timeouts. Review the query to see if it can be optimized for performance.
  3. Check Database Settings: Look at the database configuration parameters that might cause early cancellation of queries, such as statement_timeout, lock_timeout, or idle_in_transaction_session_timeout.
  4. Examine System Resources: Ensure that the database server has sufficient resources (CPU, memory, I/O) to execute the query. Resource contention can lead to query cancellation in some cases.

Here are some examples and sample code to illustrate how to address the 57014 error:

-- Example 1: Manually canceling a query
SELECT pg_cancel_backend(pid) FROM pg_stat_activity WHERE query = 'SELECT * FROM my_large_table';

-- Example 2: Query running longer than the statement_timeout
SET statement_timeout = '5s';
SELECT * FROM my_large_table;
-- If the above query takes longer than 5 seconds, it will be canceled, raising the 57014 error.

-- To fix this, you can optimize the query or adjust the timeout setting:
SET statement_timeout = '10min'; -- Increase the timeout
-- or
SET statement_timeout = 0; -- Disable the timeout

-- Example 3: Lock timeout causing query cancellation
SET lock_timeout = '2s';
-- Attempting to update a row that is locked by another transaction
UPDATE my_table SET column = value WHERE id = 1;
-- If the lock is not acquired within 2 seconds, the query will be canceled.

-- To fix this, you can increase the lock_timeout or ensure that the conflicting transaction completes faster:
SET lock_timeout = '1min'; -- Increase the lock timeout
-- or
-- Make sure that other transactions holding locks commit or roll back promptly.

-- Example 4: System-level interruption
-- This could happen during a server shutdown or when the system decides to cancel the query due to resource constraints.
-- There is no specific code example for this, but you should ensure that your database server is not being overloaded and has adequate resources.

When dealing with a 57014 error:

  • If the cause is a manual cancellation, no action may be necessary if the cancellation was intended.
  • If the cause is a timeout parameter, consider whether the timeout is too aggressive for the workload and adjust accordingly.
  • If the cause is related to system resources, you may need to optimize the query, add indexes, or upgrade the hardware to handle the load better.

Remember to look at the PostgreSQL logs for more details on the error, which can provide additional context to help diagnose and fix the issue. If the query is essential and must be run without interruption, consider scheduling it during off-peak hours or when the system is under less load.

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