https://github.com/san650/one_plus_n_detector

Elixir library to help you detect 1+n queries in applications using Ecto
https://github.com/san650/one_plus_n_detector

ecto elixir phoenix sql

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Elixir library to help you detect 1+n queries in applications using Ecto

• Host: GitHub
• URL: https://github.com/san650/one_plus_n_detector
• Owner: san650
• License: other
• Created: 2018-07-22T23:53:38.000Z (over 6 years ago)
• Default Branch: master
• Last Pushed: 2022-12-09T09:18:29.000Z (almost 2 years ago)
• Last Synced: 2024-03-15T01:23:09.607Z (8 months ago)
• Topics: ecto, elixir, phoenix, sql
• Language: Elixir
• Size: 10.7 KB
• Stars: 25
• Watchers: 2
• Forks: 4
• Open Issues: 1
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

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README

        
# OnePlusNDetector

This library helps detect 1+n SQL queries in your application. This is a common problem when working with ORMs like Ecto.

## What is the 1+n problem?

When you have a parent-child relationship like a `has_many`, `has_one` or `belongs_to` you might load your parent records with one query and then **for each record**, trigger another SQL statment to load the related children.

Let's say you have the following Ecto schemas

```elixir

defmodule User do

  use Ecto.Schema

  schema "users" do

    has_one :details, Details

  end

end

defmodule Details do

  use Ecto.Schema

  schema "users_details" do

    belongs_to :user, User

  end

end

```

You could load all the users with its respective details the following way (**wrong way**)

```elixir

User

|> Repo.all

|> Enum.map(& %{&1 | details: Repo.get(&1.details_id)})

```

You can query all users and then for each record that it's returned you can query it's user details. This implementation falls into the 1+N problem because the first query returns N records and for each record you trigger an additional SQL query, having in total 1+N SQL queries issued to your DB.

The number of queries can be reduced to two by just using a [preload](https://hexdocs.pm/ecto/Ecto.Query.html#preload/3) statement.

```elixir

User

|> preload(:details)

|> Repo.all

```

This library helps you detect these cases by triggering a warning in your query log.

## Usage

Add an extra logger to Ecto repo in development.

```elixir

config :my_app, MyApp.Repo, loggers: [

  {OnePlusNDetector, :analyze, []},

  {Ecto.LogEntry, :log, []}

]

```

## Documentation

Documentation can be found at [https://hexdocs.pm/one_plus_n_detector](https://hexdocs.pm/one_plus_n_detector).

## Installation

**This library should be used only on development**

```elixir

def deps do

  [

    {:one_plus_n_detector, "~> 0.1.0", only: :dev}

  ]

end

```

Remember to **not add** `:one_plus_n_detector` to your applications list!

## License

one_plus_n_detector is licensed under the MIT license.

See [LICENSE](./LICENSE) for the full license text.