Plasm

A generic composable query library for Ecto.

:heart::heart::heart: Ecto, :cry::cry::cry: because I have to implement my own composable query functions for things like counting records, getting a random record and whatnot in all my models/projects.

NO MORE.

Plasm provides a set of generic, composable, higher-level functions that make working with Ecto more joyful and productive.

Design Objectives

• Work alongside Ecto.Query so both can be imported without conflict
• Avoid reimplementing basic Ecto.Query functionality where possible
• Provide syntactic sugar for common queries (e.g., see count and distinct_by)
• Easy integration with Phoenix
• Permissive API (e.g., most functions that accept an atom will alternatively accept a string)

Examples

Instead of writing this in your model:

defmodule MyGhostBustingApp.ProtonPack
  ...

  def count(query) do
    for q in query,
    select: count(q.id)
  end

  ...
end

And using it this way:

ProtonPack |> ProtonPack.count |> Repo.one

Just use Plasm:

ProtonPack |> Plasm.count |> Repo.one

More examples:

PkeMeter |> Plasm.later_than(:updated_at, "2016-01-04T14:00:00Z") |> Repo.all

GhostTrap |> Plasm.find([3,6,9]) |> Repo.all

StayPuftMarshmallowMan |> Plasm.random |> Repo.one

Using in Models

You can import Plasm and use it directly in your models:

defmodule MyApp.SomeModel do
  import Ecto.Query
  import Plasm

  ...

  def random_distinct_names_by_order_of_insertion(query, n) do
    query
    |> order_by(asc: :inserted_at)
    |> distinct_by(:name)
    |> random(n)
  end
end

Using with Phoenix

If you want Plasm to be universally accessible in all your Phoenix models, you can add it to web.ex:

defmodule MyApp.Web do
  ...

  def model do
    quote do
      ...

      import Plasm
    end
  end
end

API

Plasm.at(query, field_name, ecto_date_time)
Plasm.at_or_later_than(query, field_name, ecto_date_time)
Plasm.at_or_earlier_than(query, field_name, ecto_date_time)
Plasm.average(query, field_name)
Plasm.count(query)
Plasm.count_distinct(query, field_name)
Plasm.distinct_by(query, field_name)
Plasm.earlier_than(query, field_name, ecto_date_or_date_time)
Plasm.earliest(query, field_name)
Plasm.earliest(query, field_name, n)
Plasm.find(query, primary_key)
Plasm.find(query, primary_keys)
Plasm.later_than(query, field_name, ecto_date_or_date_time)
Plasm.latest(query, field_name)
Plasm.latest(query, field_name, n)
Plasm.maximum(query, field_name)
Plasm.minimum(query, field_name)
Plasm.on(query, field_name, ecto_date)
Plasm.on_or_later_than(query, field_name, ecto_date)
Plasm.on_or_earlier_than(query, field_name, ecto_date)
Plasm.random(query)
Plasm.random(query, n)
Plasm.total(query, field_name)
Plasm.where_all(query, field_names_and_values)
Plasm.where_none(query, field_names_and_values)

Why not use shorter names, like avg, sum, etc.?

To avoid conflicts when importing. For instance, Plasm.min\2 and Plasm.max\2 would conflict with Kernel.min\2 and Kernel.max\2, so if you're importing them, you'd need to prefix your calls with __MODULE__; e.g., __MODULE__.min(query, field_name). This sucks, so I chose to go with the longer versions and tried to stay consistent.

Note On DB Support

Guaranteed to work with Postgres; others might work but haven't been tested.

Note On Query Syntaxes

Ecto supports two query syntaxes, keyword and query expression.

Example of the keyword syntax:

def for_name_or_age(query, name, age) do
  for x in query,
  where: x.name == ^name or x.age == ^age
end

Example of the query expression syntax:

def for_name_or_age(query, name, age) do
  query
  |> where([x], x.name == ^name or x.age == ^age)
end

The keyword syntax is a bit easier on the eyes, but is not fully compatible with Plasm. A case can be made for sticking with the query expression syntax for all functions that are meant to be composable, and especially if you plan to use Plasm or something like it.

Inspiration

Many thanks to Drew Olson for his talk at ElixirConf 2015 and insightful blog post on the subject of composable Ecto queries.

Also thanks to Henrik Nyh for his Ectoo project, which has similar aims.

TODO:

• Tests
• Hex docs

Installation

Add Plasm to your list of dependencies in mix.exs:

def deps do
  [{:plasm, "~> 2.0"}]
end

Ensure Plasm is started before your application:

def application do
  [
    applications: [
      ...
      :plasm
      ...
    ]
  ]
end

If you want to be on the bleeding edge, track the master branch of this repo:

{:plasm, git: "https://github.com/facto/plasm.git", branch: "master"}

Copyright and License

Copyright (c) 2016-2020 Joshua Rieken.

Plasm source code is licensed under the Apache 2 License (see LICENSE.md).