Level 33
The functionality to select columns for polymorphic relations was added in this PR https://github.com/laravel/framework/pull/25662
I guess all columns have to be available in all the related tables if you want to eager load them.
May 16, 2020
4
Level 2
Select specific fields by polymorphic type while using 'with'?
class Lesson extends Model
{
public function content()
{
return $this->morphTo();
}
}
Schema::create('lessons', function (Blueprint $table) {
$table->id();
$table->unsignedBigInteger('channel_id');
$table->string('title');
$table->nullableMorphs('content');
$table->timestamps();
$table->foreign('channel_id')->references('id')->on('channels')->onDelete('cascade');
});
Schema::create('videos', function (Blueprint $table) {
$table->id();
$table->string('title');
$table->string('size');
$table->string('path');
$table->timestamps();
});
Schema::create('articles', function (Blueprint $table) {
$table->id();
$table->string('body');
$table->string('reading_time');
$table->timestamps();
});
A lesson can have a Video or an Article as a content, now everything works fine, But I am having a trouble in selecting specific fields while eager loading the content.
Channel::whereId($channelId)->with(['lessons'=> function ($query) {
$query->with('content:id,size');
}])->first();
Since Lesson content can be Video or an Article an error will be shown:
Column not found: 1054 Unknown column 'size' in 'field list' (SQL: select `id`, `size` from `articles` where `articles`.`id` in (168))
How can I the fields I want while eager loading based on the polymorphic relation type?
Level 2
Yes that needs all the related tables has the same fields, so If articles table has a reading_time field, the videos table must have a reading_time for this to work.
Is there any workaround out there for this case?
Level 2
Any workaround for this?
Level 1
Just for the people like me, I found a workaround, you can easily make this work using MySQL alias.
<?php
use Illuminate\Database\Migrations\Migration;
use Illuminate\Support\Facades\DB;
class AddAliasColumnsToShopsTable extends Migration
{
/**
* Run the migrations.
*
* @return void
*/
public function up()
{
// Assuming you have a table called 'shops' with an existing column named 'title'
// Add the alias column 'name' using DB::raw()
DB::statement('ALTER TABLE shops ADD name varchar(45) AS (title) VIRTUAL');
}
/**
* Reverse the migrations.
*
* @return void
*/
public function down()
{
// Drop the alias column 'name'
DB::statement('ALTER TABLE shops DROP COLUMN name');
}
}
And in your code using eagle loading, you can do
return $video->comments()->getQuery()->with('person:id,name')->paginate();
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