Extension loading

[warmwaffles]

I want to look into loading an extension or two from this following repository

https://github.com/nalgeon/sqlite-plus

Specifically the unicode upper and lower support. But I would love to figure out if we can support extension loading and maybe ship a way to load them. Whether it be through adding an extra dependency something like exqlite_unicode_ext that we provide some loading hooks.

Thoughts at @kevinlang ?

[kevinlang]

I think that is worthwhile to add. I can't think of a great way to do it off the top of my head, though.

One idea:

1. Add ability to configure exqlite a list of modules that subscribe to some interface, a method of which could be called to get the path to the relevant .so or .dll that is created during module compilation. The user would add those hex libraries as dependency and wire them up to the exqlite app. The exqlite app would then ensure that at db-open time that the connection also loads the relevant extension(s)

Given that all we need, in the end, is a path to the .so file and a way of telling exqlite about it, there may be a way to do it with almost no Elixir code at all. Looks like :code.priv_dir gets us that.

So maybe something like:

Application.put_env(:exqlite, :load_extensions, ["#{:code.priv_dir(:exqlite_unicode_ext)}/ext.so"])

With there being a convention in this scenario, I guess, of making the name of the .so or .dll always ext, or perhaps the package name itself.

So all the package would need to do is to compile the extension more or less and ensure it outputs a library file to the correct location in priv/.