I encountered a situation where I needed to update some configuration settings for PostgresSQL. However, I was unsure whether it required a restart upon configuration change.

Restarting the service means downtime and it’s not feasible for the production system. That’s why it’s a crucial decision.

Upon research, I found a solution via the Postgres email list [1]. Hence I am sharing it in this post.

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Imaging we want to update max_slot_wal_keep_size config parameter. Therefore, we will run the following query.

SELECT pending_restart , context , name, setting  
FROM pg_catalog.pg_settings  
WHERE name = 'max_slot_wal_keep_size';

Here is the outcome of the above query.

pending_restart will tell you whether you need to restart the service or not. According to this mailing list [1],

when the context is postmaster, it requires a restart otherwise not.

Also,

You will immediately observe a change in the configuration when it does not require a restart as opposed to those that require a restart.

You can find a list of parameters that requires a restart using the following query.

SELECT pending_restart , context , name, setting  
FROM pg_catalog.pg_settings  
WHERE context = 'postmaster';

Thanks for reading.

Originally posted on medium

Resources

[1] postgres mailing list

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