Why is Laravel Lighthouse GraphQL running multiple MySQL queries (not eager loading)? - laravel

Question

I am new to GraphQL and Lighthouse.
My understanding from https://lighthouse-php.com/4.0/performance/n-plus-one.html#eager-loading-relationships is that for a nested GraphQL query, "Under the hood, Lighthouse will batch the relationship queries together in a single database query."
However, I see in the logs all of these queries where there should be only 1:
select count(*) as aggregate from `posts`
select * from `posts` order by `created_at` asc limit 20 offset 0
select * from `post_files` where `post_files`.`post_id` in (249, 5...
select * from `post_tags` where `post_tags`.`post_id` in (249, 5...
select * from `comments` where `comments`.`post_id` in (249, 5...
select * from `files` where `files`.`id` in (269, 615, ...
select * from `tags` where `tags`.`id` in (2, 3, 4, ...
Here is my GraphQL query:
gql`
query Posts($page: Int) {
posts(
first: 20
page: $page,
orderBy: { field: CREATED_AT, order: ASC }
) {
paginatorInfo {
currentPage
hasMorePages
total
}
data {
id
content
created_at
postFiles {
file {
id
original_name
extension
}
}
postTags {
id
tag {
id
label
}
}
comments {
id
user_id
message
created_at
seen_at
}
}
}
}
`;
My schema.graphql has the right #belongsTo and #hasMany directives:
"A date string with format `Y-m-d`, e.g. `2011-05-23`."
scalar Date #scalar(class: "Nuwave\\Lighthouse\\Schema\\Types\\Scalars\\Date")
"A datetime string with format `Y-m-d H:i:s`, e.g. `2018-05-23 13:43:32`."
scalar DateTime
#scalar(class: "Nuwave\\Lighthouse\\Schema\\Types\\Scalars\\DateTime")
"A datetime and timezone string in ISO 8601 format `Y-m-dTH:i:sO`, e.g. `2020-04-20T13:53:12+02:00`."
scalar DateTimeTz
#scalar(class: "Nuwave\\Lighthouse\\Schema\\Types\\Scalars\\DateTimeTz")
type Comment {
id: Int!
user: User! #belongsTo
user_id: Int!
post: Post! #belongsTo
post_id: Int!
message: String!
emailed_at: DateTime
seen_at: DateTime
created_at: DateTime!
modified_at: DateTime!
}
type File {
id: Int!
original_name: String!
extension: String!
postFiles: [PostFile!]! #hasMany
}
type Post {
id: Int!
user: User! #belongsTo
user_id: Int!
content: String
origin: String
created_at: DateTime!
modified_at: DateTime!
postFiles: [PostFile!]! #hasMany
comments: [Comment!]! #hasMany
postTags: [PostTag!]! #hasMany
}
type PostFile {
post: Post! #belongsTo
post_id: Int!
file: File! #belongsTo
file_id: Int!
}
type PostTag {
id: Int!
post: Post! #belongsTo
post_id: Int!
tag: Tag! #belongsTo
tag_id: Int!
created_at: DateTime!
modified_at: DateTime!
}
type Tag {
id: Int!
label: String!
hash: String!
created_at: DateTime!
modified_at: DateTime!
postTags: [PostTag!]! #hasMany
}
type User {
id: Int!
email: String!
password: String!
salt: String
db_key: String
created_at: DateTime!
modified_at: DateTime!
posts: [Post!]! #hasMany
comments: [Comment!]! #hasMany
}
type Query {
comments: [Comment!]! #all
files: [File!]! #all
posts(
orderBy: _ #orderBy(columns: ["id", "created_at"], order: ASC)
): [Post!]! #paginate(defaultCount: 20)
post(id: ID! #eq): Post #find
postFiles: [PostFile!]! #all
postTags: [PostTag!]! #all
tags: [Tag!]! #all
users: [User!]! #all
}
My Laravel models have all the right relationships. E.g. class Post has:
public function comments() {
return $this->hasMany(Comment::class, Comment::POST_ID);
}
And class Comment has:
public function post() {
return $this->belongsTo(Post::class);
}
and so on.

Answer 1

You must use Type hinting
import these types
use Illuminate\Database\Eloquent\Relations\HasMany;
And
use Illuminate\Database\Eloquent\Relations\BelongsTo;
public function post() : BelongsTo {
return $this->belongsTo(Post::class);
}