Laravel inserting parent child fails inside transaction - php

Question

I am trying to perform 2 inserts, in 2 tables table are constrained via a foreign key. These 2 operations MUST be performed inside a transaction to prevent eventual failures. (In reality I need to perform more inserts on more tables so transactions are important; but the 2 tables in this example are enough to replicate the problem)
The database driver is pgsql
SomeRepo.php (Tried it with the the transaction closure variant as well)
DB::beginTransaction();
try {
$parentData = [
'name' => 'Parent name'
];
$parent = new Parent($parentData);
$parent->save();
$childData = [
// Tried it with and without setting "parent_id" here
'parent_id' => $parent->id,
'name' => 'Child name'
];
$child = new Child($childData);
$parent->children()->save($child);
DB::commit();
} catch (Exception $e) {
DB::rollback();
}
Parent.php
protected $fillable = [
'name'
];
public function children()
{
return $this->hasMany(Child::class);
}
Child.php
protected $fillable = [
'name', 'parent_id'
];
Execution fails when trying to insert the child row, with the return parent id.
insert or update on table "child" violates foreign key constraint "child_parent_id_foreign"
EDIT
Child table SQL:
DROP TABLE IF EXISTS "public"."child";
CREATE TABLE "public"."child" (
"id" int4 NOT NULL DEFAULT nextval('child_id_seq'::regclass),
"parent_id" int4 NOT NULL,
"is_read" bool NOT NULL DEFAULT false,
"created_at" timestamp(0) DEFAULT now(),
"updated_at" timestamp(0),
"deleted_at" timestamp(0)
)
;
ALTER TABLE "public"."child" OWNER TO "my_user";
-- ----------------------------
-- Primary Key structure for table child
-- ----------------------------
ALTER TABLE "public"."child" ADD CONSTRAINT "child_pkey" PRIMARY KEY ("id");
-- ----------------------------
-- Foreign Keys structure for table child
-- ----------------------------
ALTER TABLE "public"."child" ADD CONSTRAINT "child_parent_id_fkey" FOREIGN KEY ("parent_id") REFERENCES "public"."parent" ("id") ON DELETE NO ACTION ON UPDATE NO ACTION DEFERRABLE INITIALLY DEFERRED;

Answer 1

To save data in related table use this
Parent::create(['name'=>'parent name']); //save in parent table
$lastId = Parent::query()->max('id'); //get last inserted row id
$parent = App\Parent::find($lastId);
$child = $parent->children()->create([
'message' => 'A new comment.',
]);
You can also use createMany method
$parent = App\Parent::find($lastId);
$parent->children()->createMany([
[
'message' => 'A new comment.',
],
[
'message' => 'Another new comment.',
],
]);

Answer 2

Try it with this code by using create and createMany on the relation of the Parent model:
// Create the parent object.
$parent = Parent::create([
'name' => 'Parent 1'
]);
// Insert one.
$child = $parent->children()->create([
'name' => 'Child 1',
]);
// Insert many.
$parent->children()->createMany([
[
'name' => 'Child 2',
],
[
'name' => 'Child 3',
],
]);

Answer 3

You can try this one
try {
DB::beginTransaction();
$parent = Parent::create([
'name' => 'Parent name'
]);
$parent->children()->create([
'parent_id' => $parent->id,
'name' => 'Child name'
]);
DB::commit();
} catch (Exception $e) {
DB::rollback();
}

Answer 4

alter the foreign key-- run this sql on the database
alter table child drop constraint child_parent_id;
alter table child add foreign key (parent_id) references parent(id) deferrable initially deferred;
This will allow you to create the child or parent in either order and the constraint will not be validated until the commit. It should not be necessary in this case-- however, It does depend on how your IDs are generated.

Answer 5

children function needs a middle table change it to :
public function children()
{
return $this->belongsToMany(Child::class);
}
and don't do this $parent->children()->save($child);.
or if you want to go that way make child_parent table, with 2 fields child_id and parent_id.