Elixir without Ecto, A thin Postgrex wrapper

db.ex

# see https://www.openmymind.net/Elixir-Without-Ecto/

defmodule A.DB do
	defmacro __using__(_) do
		quote location: :keep do
			@name __MODULE__

			def child_spec(opts) do
				%{
					id: __MODULE__,
					start: {__MODULE__, :start_link, opts}
				}
			end

			def start_link(config) do
				defaults = [name: @name, pool_size: 5]
				config = Keyword.merge(defaults, config)
				Postgrex.start_link(config)
			end

			def ok!(sql, values), do: ok!(@name, sql, values, [])
			def ok!(conn, sql, values, opts \\ []) do
				query!(conn, sql, values, opts)
				:ok
			end

			def affected!(sql, values), do: affected!(@name, sql, values, [])
			def affected!(conn, sql, values, opts) do
				query!(conn, sql, values, opts).num_rows
			end

			def scalar!(sql, values), do: scalar!(@name, sql, values, [])
			def scalar!(conn, sql, values, opts \\ []) do
				case query!(conn, sql, values, opts) do
					%{rows: []} -> nil
					%{rows: [[value]]} -> value
					_ -> raise "scalar returned multiple columns and/or rows"
				end
			end

			def row!(sql, values), do: row!(@name, sql, values, [])
			def row!(conn, sql, values, opts \\ []) do
				case query!(conn, sql, values, opts) do
					%{rows: []} -> nil
					%{rows: [row]} -> row
					_ -> raise "row! returned multiple rows"
				end
			end

			def map!(sql, values), do: map!(@name, sql, values, [])
			def map!(conn, sql, values, opts \\ []) do
				r = query!(conn, sql, values, opts)
				case r.rows do
					[] -> nil
					[row] -> A.DB.mapify(r.columns, row)
					_ -> raise "map returned multiple rows"
				end
			end

			def maps!(sql, values), do: maps!(@name, sql, values, [])
			def maps!(conn, sql, values, opts \\ []) do
				case query!(sql, values) do
					%{rows: []} -> nil
					%{rows: rows, columns: columns} ->
						Enum.map(rows, fn row -> A.DB.mapify(columns, row) end)
					_ -> raise "maps! returned multiple rows"
				end
			end

			def rows!(sql, values), do: rows!(@name, sql, values, [])
			def rows!(conn, sql, values, opts \\ []) do
				query!(conn, sql, values, opts).rows
			end

			def transaction!(fun, opts \\ []) do
				case Postgrex.transaction(@name, fun, opts) do
					{:ok, res} -> res
					{:error, :rollback} -> raise "transaction! rollback"
					err -> err
				end
			end

			def query!(sql, values), do: query!(@name, sql, values, [])
			def query!(conn, sql, values, opts \\ []) do
				Postgrex.query!(conn, sql, values, opts)
			end
		end
	end

	def mapify(columns, row) do
		columns
		|> Enum.zip(row)
		|> Map.new()
	end
end