Reorderex

An elixir helper library for database list reordering functionality.

Installation

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

def deps do
  [
    {:reorderex, "~> 0.2.0-beta"}
  ]
end

You can optionally add Reorderex.Clock to make Reorderer.next_score become strictly monotonic.

children = [
  #...
  Reorderex.Clock
  #...
]

Usage with Ecto

Table-wise ordering

Schema

defmodule Photo do
  @moduledoc false
  use Ecto.Schema

  schema "photos" do
    field(:score, :binary, autogenerate: {Reorderex, :next_score, []})
  end
end

Move and entity to after an entity

import Reorderex.Ecto

photo
|> insert_after(photo1.id, Repo)
|> Repo.update()

Move and entity to the first

import Reorderex.Ecto

photo
|> insert_after(nil, Repo)
|> Repo.update()

Shared-table ordering

defmodule Photo do
  @moduledoc false
  use Ecto.Schema

  schema "photos" do
    field user_id, :binary
    field :score, :binary, autogenerate: {Reorderex, :next_score, []}
  end
end

import Reorderex.Ecto

query = Photo |> where([p], p.user_id = ^user_id)

photo
|> insert_after(photo1.id, Repo, query: query)
|> Repo.update()

The docs can be found at https://hexdocs.pm/reorderex.