shared pivot table for inherited table - php

Question

I have 3 tables, people, instructors, and trainees. instructor and trainees inherit from people. both three table have relation to fee_instructor table. here is all the models.
// Person.php
class Person extends \Eloquent {
// Add your validation rules here
public static $rules = [
// 'title' => 'required'
'name'=>'required',
'institution_id'=>'required',
'pob'=>'required',
'dob'=>'required'
];
// Don't forget to fill this array
protected $fillable = [
'name',
'title',
'position',
'institution_id',
'pob',
'dob',
'photo',
'last_education',
'nip',
'role_id'
];
public function fee(){
return $this->belongsToMany('Fee', 'fee_instructor', 'person_id');
}
}
// Instructor.php
class Instructor extends \Eloquent {
// Add your validation rules here
public static $rules = [
// 'title' => 'required'
];
// Don't forget to fill this array
protected $fillable = [
'name',
'title',
'position',
'institution_id',
'pob',
'dob',
'photo',
'email',
'last_education',
'nip'
];
public function fee(){
return $this->belongsToMany('Fee', 'fee_instructor', 'person_id');
}
}
// Trainee.php
class Trainee extends \Eloquent {
// Add your validation rules here
public static $rules = [
// 'title' => 'required'
];
// Don't forget to fill this array
protected $fillable = [
'name',
'title',
'position',
'institution_id',
'pob',
'dob',
'photo',
'last_education',
'nip',
'reg_date',
'company_name',
'marital_status',
'email'
];
public function fee(){
return $this->belongsToMany('Fee', 'fee_instructor', 'person_id');
}
}
// Fee.php
class Fee extends \Eloquent {
// Add your validation rules here
public static $rules = [
// 'title' => 'required'
];
// Don't forget to fill this array
protected $fillable = ['name', 'tarif', 'unit_id'];
public function unit(){
return $this->belongsTo('Unit');
}
public function instructor(){
return $this->belongsToMany('Instructor', 'fee_instructor');
}
public function person(){
return $this->belongsToMany('Person', 'fee_instructor');
}
public function trainee(){
return $this->belongsToMany('Trainee', 'fee_instructor');
}
}
when i try to update an entry that is not belongs to instructor (in both person or trainee), laravel throw the following error.
SQLSTATE[23503]: Foreign key violation: 7 ERROR: insert or update on table "fee_instructor" violates foreign key constraint "fee_instructor_instructor_id_foreign" DETAIL: Key (person_id)=(5) is not present in table "instructors".
how is the correct way to use the pivot table for these scenario?

Answer 1

Ah so your using postgresql. That' why I thought it was weird that you were talking about table inheritance. Take note that based on the docs http://www.postgresql.org/docs/9.0/static/ddl-inherit.html
Inheritance does not automatically propagate data from INSERT or COPY commands to other tables in the inheritance hierarchy.
INSERT always inserts into exactly the table specified.
...
In some cases it is possible to redirect the insertion using a rule (see Chapter 37).
So if you're not in the bounds of the rule, you may be incorrectly assuming that a row that exists in instructor also exists in the super-table person and vice-versa. You're update/insert on fee_instructor is failing simply because a row with person_id = 5 does not exist in the instructor table. It may exist in the person table but that is irrelevant. If it does not exist in instructor it wont work.
If you scroll through the docs about inheritance, you will also come up with the caveats of using inheritance:
A serious limitation of the inheritance feature is that indexes (including unique constraints)
and foreign key constraints only apply to single tables, not to their inheritance children.
So if you really want FK relationships with fee_instructor for both instructor and trainee then separate FKs have to exist for each table which I'm assuming you already have in place.
Please also take not that eloquent's regular relationship does not work well with the idea of inheritance. However, you may be able to achieve an inheritance type of behavior using polymorphic relations: http://laravel.com/docs/4.2/eloquent#polymorphic-relations