spicychickensauce
Support both sqlite and postgres in ash application
I’m evaluating migrating an existing application to ash and it’s looking pretty good so far.
However, I got stuck at this: My app currently supports both sqlite and postgres, configured via a compile time setting. (I need sqlite support because my app is also bundled on android, postgres is used on servers)
I cannot figure out how to make that work with ash.
The problem is in the resources. I tried this:
if App.Config.use_sqlite?() do
use Ash.Resource,
domain: App,
data_layer: AshSqlite.DataLayer
else
use Ash.Resource,
domain: App,
data_layer: AshPostgres.DataLayer
end
# same conditional for the `postgres` and `sqlite` expressions
actions do
...
However, I get a compile error:
error: undefined function actions/1 (there is no such import)
│
12 │ actions do
This is very weird, since when I manually comment out the appropriate use it compiles just fine.
What is happening here? Why does this conditional compilation logic not work with ash?
It used to work just fine when I did that in my ecto repo to configure the appropriate adapter…
Marked As Solved
zachdaniel
try this instead:
use mix ash.gen.base_resource MyApp.Resource and then modify it to look something like this:
# use it in the resources like this
use MyApp.Resource
defmodule MyApp.Resource do
defmacro __using__(opts) do
data_layer =
if App.Config.use_sqlite?() do
AshSqlite.DataLayer
else
AshPostgres.DataLayer
end
opts = Keyword.put_new(opts, :data_layer, data_layer)
quote do
use Ash.Resource, unquote(opts)
end
end
end
Also Liked
zachdaniel
Simpler would be this:
defmodule MyApp.Resource do
defmacro __using__(opts) do
{data_layer, extension_to_add} =
if App.Config.use_sqlite?() do
{AshSqlite.DataLayer, AshPostgres.DataLayer}
else
{AshPostgres.DataLayer, AshSqlite.DataLayer}
end
{table, opts} = Keyword.pop(opts, :table)
opts =
opts
|> Keyword.put_new(:data_layer, data_layer)
|> Keyword.update(:extensions, [extension_to_add], &[extension_to_add | &1])
quote do
use Ash.Resource, unquote(opts)
postgres do
table unquote(table)
repo YourRepo
end
sqlite do
table unquote(table)
repo YourRepo
end
end
end
end
You can use the postgres and sqlite extensions multiple times, and can add it as an extension without making it the data layer so that when you have special sqlite or postgres specific things in a resource, you can just do postgres do ... and not include table.
Last Post!
spicychickensauce
Great, then I’ll go with that. Seems the most flexible and DRY approach.
Thank you very much for the help!
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