Can query results for eloquent related eloquent models be re-used? - php

Question

In my Post model there is an author relationship belonging to a User (related by the typical user_id field in the database table) to represent the author of the post and there is also a submitter relationship to represent a user that submitted a post for review. The submitter user could be the same as the author user or it could be a different user.
Here is the migration:
Schema::create('posts', function(Blueprint $table) {
$table->increments('id');
$table->string('code');
$table->integer('user_id');
$table->integer('submitter_id');
});
Here is the Post model:
class Post extends Model
{
protected $guarded = [];
public function author()
{
return $this->belongsTo(User::class);
}
public function submitter()
{
return $this->belongsTo(User::class);
}
}
When querying for a post by id I can eager load those relationships
$post = Post::with(['submitter', 'author'])->find($id);
If the seeder inserts two posts, one where the user_id and the submitter_id are the same, then one where they are different:
DB::table('posts')->insert([
'user_id' => 1,
'submitter_id' => 1
]);
DB::table('posts')->insert([
'user_id' => 1,
'submitter_id' => 2
]);
When querying for the second post I expect it to run two queries for the different users, since the user_id and submitter_id are different:
[2023-02-02 17:51:48] testing.INFO: sql: select * from "users" where "users"."id" in (2)
[2023-02-02 17:51:48] testing.INFO: bindings: array (
)
[2023-02-02 17:51:48] testing.INFO: query time: 0.2
[2023-02-02 17:51:48] testing.INFO: sql: select * from "users" where "users"."id" in (1)
[2023-02-02 17:51:48] testing.INFO: bindings: array (
)
[2023-02-02 17:51:48] testing.INFO: query time: 0.18
However for the first post, the user_id and the submitter_id are the same, yet a separate query is run to get each record:
[2023-02-02 17:51:48] testing.INFO: sql: select * from "users" where "users"."id" in (1)
[2023-02-02 17:51:48] testing.INFO: bindings: array (
)
[2023-02-02 17:51:48] testing.INFO: query time: 0.15
[2023-02-02 17:51:48] testing.INFO: sql: select * from "users" where "users"."id" in (1)
[2023-02-02 17:51:48] testing.INFO: bindings: array (
)
[2023-02-02 17:51:48] testing.INFO: query time: 0.13
While I understand that there is a possibility that the two queries could return different results (e.g. if a separate query was run in a separate process to update the user record), the chances of that are dramatically low.
Can the query (and its results) be used for both relations when the primary key is the same? If so, how can this be achieved?

Answer 1

It can't. Two different relationships is considered as two different objects by Laravel, even when it's referencing to the same table.
The doc also states that eager-load feature exists to "alleviates the "N + 1" query problem", not the problem that you asked about.
You can make your own query using the query-builder if you want to retrieve it in one query. But that will gives you a different returned data structure and adds a bit of complexity.