phoenix ecto preload

To preload associations in Elixir Phoenix Ecto, you can use the preload function. The preload function is used to load associated data along with the main query, reducing the number of database queries required.

To use preload, you first need to define the associations in your Ecto schema using the has_many, belongs_to, or has_one macros. Once the associations are defined, you can use the preload function in your queries to load the associated data.

Here's an example of how to use preload in Elixir Phoenix Ecto:

# Define the associations in your schema
defmodule MyApp.User do
  use Ecto.Schema

  schema "users" do
    has_many :posts, MyApp.Post

defmodule MyApp.Post do
  use Ecto.Schema

  schema "posts" do
    belongs_to :user, MyApp.User

# Preload the associated data in your query
query = from u in MyApp.User,
        preload: [:posts]

result = MyApp.Repo.all(query)

In the example above, we define a one-to-many association between User and Post schemas. We use the has_many macro in the User schema and the belongs_to macro in the Post schema to define the association.

To preload the associated posts when querying for users, we include preload: [:posts] in the query. This tells Ecto to load the associated posts along with the users in a single query.

Finally, we execute the query using MyApp.Repo.all(query) to retrieve the results.

By using preload, you can efficiently load associated data in Elixir Phoenix Ecto, reducing the number of database queries and improving performance.