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
end
end
defmodule MyApp.Post do
use Ecto.Schema
schema "posts" do
belongs_to :user, MyApp.User
end
end
# 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.