THIS IS A WORK IN PROGRESS. USE AT YOUR OWN RISK.

Snowflex ❄💪

This application encapsulates an ODBC connection pool for connecting to the Snowflake data warehouse.

Setup

The following config options can be set:

config :snowflex,
  driver: "/path/to/my/ODBC/driver" # defaults to "/usr/lib/snowflake/odbc/lib/libSnowflake.so"

Connection pools are not automatically started for you. You will need to define and establish each connection pool in your application module. Configuration values related to connection timeouts and the mapping of :null query values can be set here.

First, create a module to hold your connection information:

defmodule MyApp.SnowflakeConnection do
  use Snowflex.Connection,
    otp_app: :my_app,
    timeout: :timer.minutes(20),
    map_nulls_to_nil?: true
end

Define your configuration:

import Config

# ...

config :my_app, MyApp.SnowflakeConnection,
  connection: [
      role: "PROD",
      warehouse: System.get_env("SNOWFLAKE_POS_WH"),
      uid: System.get_env("SNOWFLAKE_POS_UID"),
      pwd: System.get_env("SNOWFLAKE_POS_PWD")
    ]

 # you may define multiple connection modules
 config :my_app, MyApp.MyOtherSnowflakeConnection,
    worker: MyApp.MockWorker # defaults to Snowflex.Worker (change for testing/development)
    connection: [
      role: "PROD",
      warehouse: System.get_env("SNOWFLAKE_ADVERTISING_WH"),
      uid: System.get_env("SNOWFLAKE_ADVERTISING_UID"),
      pwd: System.get_env("SNOWFLAKE_ADVERTISING_PWD")
    ]

The odbc driver will, by default, return :null for empty values returned from snowflake queries. This will be converted to nil by default by Snowflex. A configuration value map_nulls_to_nil? can be set to false if you do not desire this behavior.

Then, in your application module, you would start your connection:

def MyApp.Application do
  use Application

  def start(_type, _args) do

    children = [
      MyApp.SnowflakeConnection,
      MyApp.MyOtherSnowflakeConnection
    ]

    opts = [strategy: :one_for_one, name: MyApp.Supervisor]
    Supervisor.start_link(children, opts)
  end
end

Caveats

If you are planning to connect to the Snowflake warehouse, your local Erlang instance must have ODBC enabled. The erlang installed by Homebrew does NOT have ODBC support. The asdf version of erlang does have ODBC support. You will also need the Snowflake ODBC driver installed on your machine. You can download this from https://sfc-repo.snowflakecomputing.com/odbc/index.html.

Installation

The package can be installed by adding snowflex to your list of dependencies in mix.exs:

def deps do
  [
    {:snowflex, "~> 0.4.4"}
  ]
end

DBConnection Support

DBConnection support is currently in experimental phase, setting it up is very similar to current implementation with the expection of configuration options and obtaining the same results will require an extra step:

Configuration:

Setting a Module to hold the connection is very similar, but instead you’ll use Snowflex.DBConnection:

Example:

defmodule MyApp.SnowflakeConnection do
  use Snowflex.DBConnection,
    otp_app: :my_app,
    timeout: :timer.minutes(5)
end

config :my_app, MyApp.SnowflakeConnection,
  pool_size: 5, # the connection pool size
  worker: MyApp.CustomWorker, # defaults to Snowflex.DBConnection.Server
  connection: [
      role: "PROD",
      warehouse: System.get_env("SNOWFLAKE_POS_WH"),
      uid: System.get_env("SNOWFLAKE_POS_UID"),
      pwd: System.get_env("SNOWFLAKE_POS_PWD")
    ]

Usage:

After setup, you can use your connection to query:

alias Snowflex.DBConnection.Result

{:ok, %Result{} = result} = MyApp.SnowflakeConnection.execute("my query")
{:ok, %Result{} = result} = MyApp.SnowflakeConnection.execute("my query", ["my params"])

As you can see we now receive an {:ok, result} tuple, to get results as expected with current implementation, we need to call process_result/1:

alias Snowflex.DBConnection.Result

{:ok, %Result{} = result} = MyApp.SnowflakeConnection.execute("my query")

[%{"col" => 1}, %{"col" => 2}] = SnowflakeDBConnection.process_result(result)