Keeping Your PostgreSQL Database in Check: Methods for Terminating Slow Queries

1. Identify the Process ID (PID) of the query you want to stop. Use the following query in psql to see active queries and their PIDs:

SELECT * FROM pg_stat_activity WHERE state = 'active';

This will return a list of running queries, including their PIDs.

Stopping the query:

There are two main functions for terminating queries, each with a different approach:

Example (using pg_cancel_backend):

SELECT pg_cancel_backend(1234);  -- Replace 1234 with the actual PID

Additional considerations:

• You can terminate all active queries (except your own) using a query like this:

SELECT pg_cancel_backend(pid) FROM pg_stat_activity WHERE state = 'active' AND pid <> pg_backend_pid();

-- Find the PID of the query to stop (replace 1234 with the actual PID)
SELECT * FROM pg_stat_activity WHERE state = 'active';

-- Stop the query using the PID
SELECT pg_cancel_backend(1234);

This code first retrieves information about active queries using pg_stat_activity. Then, it identifies the desired query by its PID (process ID) and uses pg_cancel_backend to send a termination request to that specific process.

Terminating all active queries except your own (use with caution):

SELECT pg_cancel_backend(pid) FROM pg_stat_activity WHERE state = 'active' AND pid <> pg_backend_pid();

This code iterates through all active queries (state = 'active') using pg_stat_activity. It then checks if the process ID (PID) is different from the current session's PID (pg_backend_pid()). If it's a different process, pg_cancel_backend is used to send a termination request to that specific query. This approach should be used cautiously as it can disrupt other users.

Forcefully terminating a query using pg_terminate_backend (use with extreme caution):

-- Find the PID of the query to terminate (replace 1234 with the actual PID)
SELECT * FROM pg_stat_activity WHERE state = 'active';

-- Forcefully terminate the query using the PID
SELECT pg_terminate_backend(1234);

1. Setting Statement Timeouts:

PostgreSQL allows setting a statement timeout at the database session or server level. This automatically terminates any query exceeding the specified time limit. This is a proactive approach to prevent long-running queries from causing issues in the first place.

Here's how to set a statement timeout for the current session:

SET statement_timeout = 10000;  -- Timeout in milliseconds (10 seconds in this example)

You can set a server-wide default timeout by editing the postgresql.conf file and restarting the server. Refer to the PostgreSQL documentation for details.

1. Client-side Termination (if applicable):

If your application interacts with PostgreSQL through a client program or library, it might offer functionalities to terminate queries on the client-side. These functionalities might be specific to the client you're using. Consult the documentation for your client program/library to see if it provides such options.

1. Optimize Queries: