Wednesday, April 27, 2016

Postgres + Erlang on OS X Part 1

I've been trying to get epgsql so I can build out the database for Markov-lang.  Getting this running took some time.

First we needed to install rebar3.  You do this by running:
brew install homebrew/versions/rebar3
Once rebar3 is installed, you have to configure it to work with hex.pm.  You do this by running the following:
mkdir -p ~/.config/rebar3 
Then create the following file ~/.config/rebar3/rebar.config with the following contents:
 {plugins, [rebar3_hex]}.
(EDIT: According to Reddit user mononcqc this is only necessary if you want to publish packages not fetch them)

Then run:
rebar3 update

Now, in the directory for you project that will use postgres, create a file /Path/To/App/rebar.config with the following content:
{deps, [epgsql]}.
Now you can access epgsql by running:
rebar3 shell
It should compoile epgsql. In the REPL started by the previous command you can run:
m(epgsql).
To access this from within Emacs, start the Erlang REPL in Emacs with the following flag:
-pz _build/default/deps/epgsql/ebin 

Part 2 can be found here.
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6 comments:

  1. Craig FerryMay 25, 2016 at 12:51 AM

    Really helpful.
    I think there is a typo `rebar3s shell` should be `rebar3 shell`.
    Instruction on how emacs can pass a flag into the repl would be super helpful.

    ReplyDelete
    Replies
    1. Reza NikoopourJune 1, 2016 at 12:14 PM

      Hey Craig! Glad this helped, and thanks for catching the Typo!

      To pass flags to the Emacs Erlang shell define the following in your .emacs:

      (defun erl-shell (flags)
      "Start an erlang shell with flags"
      (interactive (list (read-string "Flags: ")))
      (set 'inferior-erlang-machine-options (split-string flags))
      (erlang-shell))

      Then to start the shell you do this will then prompt you for the flags.

      More info can be found here http://erlang.org/pipermail/erlang-questions/2007-January/024966.html.

      Delete
    2. Reza NikoopourJune 1, 2016 at 12:15 PM

      Then to start the shell you do "M-x erl-shell" this will then prompt you for the flags.

      Sorry for the double reply. Forgot to put the command in.

      Delete
    3. Craig FerryJune 8, 2016 at 11:05 AM

      Thanks for the additional information. That has saved me hours of frustration and searching around. In order to use Erlang more I need to be able to tap into legacy data we have and this has been a great help in that area.

      Delete
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