Rework sequence-based identity generation

[morozov]

Sequence-based identity values will be deprecated in DBAL 3.2.0 (doctrine/dbal#4688) and removed in 4.0.x (doctrine/dbal#4691). See the details in doctrine/dbal#4687.

The ORM currently uses this API:

orm/lib/Doctrine/ORM/Id/IdentityGenerator.php

Lines 52 to 55 in f3e55fa

	public function generate(EntityManager $em, $entity)
	{
	return (int) $em->getConnection()->lastInsertId($this->sequenceName);
	}

Please consider not relying on this API.

[greg0ire]

@beberlei I think this should go in a "DBAL 4" support project, shouldn't it? 😄

[morozov]

In fact, this functionality in the ORM could be salvaged, if necessary. I updated the subject and the description.

The DBAL doesn't support using sequence values to implement lastInsertId() because it's not thread-safe but the sequences themselves are. The ORM could generate the identity value using a sequence explicitly and pass to the INSERT w/o relying on the lastInsertId() API in the same way as it does with UUIDs, for example:

$id = $conn->execute('SELECT ' . $seqName . '.NEXTVAL FROM DUAL');
$conn->insert($table, ['id' => $id]);

In this case, the ORM should not declare the column as autoincrement and should own the sequence, unlike the current implementation when the DBAL owns it.

It is also possible to leave the sequence ownership to the DBAL and have the column always auto-incremented via a trigger. In this case, the ORM should use a query like:

INSERT INTO table VALUES (...) RETURNING id INTO :id;

And then use an out parameter to get the id.

[stof]

This is about using a SequenceGenerator instead of a IdentityGenerator then (as that's what the SequenceGenerator does)

[stof]

I suggest instead deprecating the support for sequence-based IdentityGenerator, so that projects using a platform that does not support identity columns have to use something else (for instance the SequenceGenerator)

[onurkose]

Hello, today I changed the id columns' strategy from IDENTITY to SEQUENCE in my entities after reading the deprecation messages, and now all the insert statements have null id field values if the entity is using JOINED type entity inheritance.

setIdentifierValues method of ClassMetadataInfo class sets the new ids to reflection class, but then it turns into null somehow.