There are some configuration values that are required at compile-time. This is primarily the adapter - ecto inlines some functions in the repo, based on the adapter, in order to speed-up dome hot paths.

Most of the other configuration values can be passed to the repo’s start_link function (or as options in the supervisor).

There’s a list of compile-time options and runtime options in the documentation: https://hexdocs.pm/ecto/Ecto.Adapters.Postgres.html

Ecto does not allow dynamic configuration of the DB at runtime. Your only option is to directly use the DB-Adapter to go through connection and query.

Thats at least what I understand when reading github issue #1183

Can you tell us a bit more broadly what your end result should be? I mean, I suspect you may want to do multi-tenancy by connecting to multiple databases? If this is the case then Ecto has sort of different approach, by using namespaces/prefixes rather than connecting to multiple databases.

Do you know the list of DBs upfront ? then you can setup a repo per DB

Sorry, I’m new to elixir and all this. I can see that start_link is used in the lib/myapp.ex. But I’m not sure exactly how to use Ecto.Adapters.Postgres, since there’s no function documentation in the link.

I’m inferring that the Ecto.Adapters.Postgres can be run as a child supervisor to the application. However:

• I don’t know how to change the runtime options outside of lib/myapp.ex.
• And if I inserted a Repo with bad connection login, it surfaces errors on startup.
• And if I run start_link after startup, how do I find the correct child supervisor to remove the link?

I think I just don’t have enough background to make sense of the answer right now. Are there resources you can point me to, or give some examples? Thanks.