I would prefer not to have two PostgreSQL modules. I would prefer changing the existing one to support multiple instances, e.g. by adding services.postgresql.instances and mapping services.postgresql.* to services.postgresql.instances.default if services.postgresql.enable == true.

I would prefer to unsee the existing PostgreSQL module. But since it exists (and maybe is used somewhere), let it go gracefully.

@edolstra Rather than .instances I'd go straight for services.postgresql.<instance>, as with containers. The user would certainly get an error anyway from using e.g. services.postgresql.enable, so breaking the interface shouldn't be a big problem especially after 14.12 has been branched.

In addition, I'd like to suggest an helper function e.g. multipleInstances = serviceOpts: .... Many services like pgsql can benefit from this and have a consistent interface for all other services for free.
In fact, I'm tempted to have xserver.<instance> where instance would be the vt name.

services.postgresql.<instance> makes sense.

In addition, I'd like to suggest an helper function e.g. multipleInstances = serviceOpts: .... Many services like pgsql can benefit from this and have a consistent interface for all other services for free.

We need more services to design multipleInstances.

@ip1981 multipleInstances is very trivial and the interface is going to be like what I've described, there's no need to wait for other services to design it.

What's wrong with the existing module?

services.postgresql.<instance> is not possible because it is ambiguous (since it conflicts with existing option names).

@edolstra I'm talking about completely replacing the current module with services.postgresql.<instance>. Wrong, nothing. But I'd prefer if all the services would have this format.

@edolstra I'm talking about completely replacing the current module with services.postgresql.<instance>. Wrong, nothing. But I'd prefer if all the services would have this format.

This would need some convention for inter-service dependency, though.

@7c6f434c that's right

I've opened an issue here with a proposal of mkMultiInstance and also a problem: #6784

(triage) @ip1981 @lethalman is there some news ?

Nope. Not interested anymore. https://github.com/zalora/nixsap/tree/master/modules/apps/postgresql