Best ways to play with Erlang (with dependencies) in a sandbox

Questions / Help
1

There seem to be a ton of options for playing around with Erlang and I am just lost as which option is best for certain situations.

In particular I want to play around with some Erlang database drivers. But I obviously need to load these dependencies.

Rebar3 seems like a good place to start., but what type of project should I create (what project do you create)?

And then how to actually run and play around? Use the shell? An escript? An application?

Rebar3 shell seems ideal as I think rebar3 will allow changes/recompile/rerun within it.

Thanks for any help.

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2

I personally would create an “OTP application” with rebar3:

$ rebar3 new app name=my_database
$ cd my_database
$ nano rebar.config
$ cat rebar.config
{erl_opts, [debug_info]}.
{deps, [
    epgsql,  % postgresql driver
    mysql  % mysql-otp library
]}.

{shell, [
  % {config, "config/sys.config"},
    {apps, [my_database]}
]}.

$ rebar3 upgrade
$ rebar3 shell
> {ok, C} = epgsql:connect(#{
    host => "localhost",
    username => "username",
    password => "psss",
    database => "test_db",
    timeout => 4000
}).
> epgsql:squery(C, "SELECT 1").
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3

Thanks Sergey!

Interesting. So, I am not seeing an immediate big difference between rebar3 new app and rebar3 new escript (at least for just playing around with a library or 2).

$ rebar3 new escript sandbox
$ rebar3 shell
> {ok, Db} = pgsql:connect("localhost", "postgres", "postgres", "postgres", 5432).
> pgsql:pquery(Db, "select 1 where 1 = $1" ,[1])

:point_up: using dep {deps, [{p1_pgsql, {git, "https://github.com/processone/p1_pgsql.git", {tag, "1.1.12"}}}]}.

But thanks again - this is giving me more confidence now :+1:

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4

You normally use escript if you want to create a command-line utility and app in every other case.

May I ask (as I am one of the maintainers of epgsql) why you prefer p1_pgsql over epgsql?

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5

Not my choice :laughing:

We will likely move off of it soon-ish. We have other erlang apps that do use epgsql and will probably move to that across the board.

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6

FWIW I recommend pgo. I like the design.

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