How to configure Elixir Mix project with Ecto SQLite3?

Hi

Do you have a database file? Did you run mix ecto.create?

Hi Joel, yes, the eelarve_dev.db is in the project root directory and I ran mix ecto.create. (I believe the first fact is a consequence of the second?)

Alright, that’s good. What’s the rest of your mix.exs file (and why do you have :ecto_sqlite3 as extra_application?

And do you have Eelarve.Repo defined somewhere?

E.g. taken from this guide

defmodule Eelarve.Repo do
  use Ecto.Repo,
    otp_app: :eelarve,
    adapter: Ecto.Adapters.SQLite3
end

This is my mix.exs in its entirety:

defmodule Eelarve.MixProject do
  use Mix.Project

  @name :eelarve
  @version "0.1.0"

  def project do
    [
      app: @name,
      version: @version,
      elixir: "~> 1.13",
      start_permanent: Mix.env() == :prod,
      deps: deps(),
      escript: [main_module: Eelarve.CLI]
    ]
  end

  def application do
    [
      extra_applications: [:logger, :ecto_sqlite3],
      mod: {Eelarve.Application, []}
    ]
  end

  defp deps do
    [
      ecto: "~> 3.11.2",
      money: "~> 1.12",
      ecto_sqlite3: "~> 0.16"
    ]
  end
end

I don’t know why I put :ecto_sqlite3 as an extra application. That’s just me fumbling around and see what works

The file lib/eelarve/repo.ex contains:

defmodule Eelarve.Repo do
  use Ecto.Repo,
    otp_app: :eelarve,
    adapter: Ecto.Adapters.SQLite3
end

– seems to have everything you mentioned, if I can compare correctly.

You may not be making a Phoenix project, but the Phoenix generators may be helpful for your case.

In these situations, I will commonly spin up a Phoenix project with the correct flags (see the mix phx.new docs for examples) just to see what the generators spit out. It’s surprisingly barebones if you disable all the unneeded stuff, so it shouldn’t be too difficult to check for the relevant snippets from the generated files.

Hey @arcanemachine, that’s a great idea and in fact at some point I believe I’ve done something like that in order to get going. But I inspected visually, and I may have missed some important piece when transporting bits to my already existing (tiny and DB-less) project. I’ll retry and report back on the progress

I tried harder. Generated a new project with

mix phx.new salvage_prj --database sqlite3 \
    --no-assets --no-html --no-live \
    --no-mailer --no-tailwind

Checked config.exs, application.exs, dev.exs, priv/repo/ (copied the seeds.exs), repo.ex. Same error (but somehow the output is now colorized ).

I failed to mention something that I thought was irrelevant, but now that my output is colorized it seems more important. The error is much longer than what I pasted initially, and a part of it is this, occurring several times:

15:40:14.100 [error] Process #PID<0.184.0> raised an exception
** (FunctionClauseError) no function clause matching in :filename.join/2
    (stdlib 5.2) filename.erl:454: :filename.join({:error, :bad_name}, ~c"sqlite3_nif")
    (exqlite 0.23.0) lib/exqlite/sqlite3_nif.ex:16: Exqlite.Sqlite3NIF.load_nif/0
    (kernel 9.2) code_server.erl:1398: anonymous fn/1 in :code_server.handle_on_load/5

15:40:14.102 [warning] The on_load function for module Elixir.Exqlite.Sqlite3NIF returned:
{:function_clause,
 [
   {:filename, :join, [{:error, :bad_name}, ~c"sqlite3_nif"],
    [file: ~c"filename.erl", line: 454]},
   {Exqlite.Sqlite3NIF, :load_nif, 0,
    [file: ~c"lib/exqlite/sqlite3_nif.ex", line: 16]},
   {:code_server, :"-handle_on_load/5-fun-0-", 1,
    [file: ~c"code_server.erl", ...]}
 ]}

(I asked ChatGPT, and it tried to make me implement a copy_nif function to copy a dynamic library somewhere. Didn’t work )

have you configured your database name? Also check that your path doesn’t contain strange things like folder with spaces or non-ascii.

I followed your error message, in particular this part:

(FunctionClauseError) no function clause matching in :filename.join/2
    (stdlib 5.2) filename.erl:454: :filename.join({:error, :bad_name}, ~c"sqlite3_nif")
    (exqlite 0.23.0) lib/exqlite/sqlite3_nif.ex:16: Exqlite.Sqlite3NIF.load_nif/0

So in exqlite lib/exqlite/sqlite3_nix.ex line 16 is this:

path = :filename.join(:code.priv_dir(:exqlite), ~c"sqlite3_nif")

and apparently :code.priv_dir(:exqlite) gives you an error.

Looking at the documentation of escript, it says:

priv directory support
escripts do not support projects and dependencies that need to store or read artifacts from the priv directory.

So I believe what’s happening is that exqlite wants to load the nif library from its priv directory, but that’s somehow not supported when using escript.

As a sidenote, if you just want to store some data for you CLI application and can’t make it work with SQLite, you could try cubdb.
Never used it myself but given that it doesn’t need any NIFs I guess it should work in escript.
Or, the other way around, use burrito to build your CLI application.