Updating and creating entities in same loop - symfony

Question

I have a loop that iterates through some imported Product data, and uses Doctrine2 to persist it to a database.
For each product I check to see if that productID exists already. If so, update it. If not, create it and persist it.
I do the same with associated entities, which is where I run into problems, for example each Product is related to a Manufacturer.
On each loop I will check to see is the ManufacturerID exists, and if not create/persist it.
If I create ManufacturerID=3 in one iteration, and then later on I have another product with ManufacturerID3, Doctrine doesn't know about it yet because it hasn't been flushed.
I can fix this by doing a flush() after every loop, as opposed to when the loop is completed, but I am wondering if there is a better way, maybe some way for Doctrine to search for objects with ManufacturerID=3 both in the repository and in newly persisted objects?
Flush()ing after every loop works but it doesn't seem like the right way to do it.
$manufacturer = $this->em
->getRepository('AMyBundle:Manufacturer')
->findOneByPosId($item->manufacturerID);
if (!$manufacturer)
{
$manufacturer = new Manufacturer();
$manufacturer->setPosId($item->manufacturerID);
$this->em->persist($manufacturer);
}

Answer 1

You know what they say: "Early optimization is the root of all evil" D. Knuth
Check this simple optimization and if you need better times then pull up your sleeves and go down, otherwise just move on.
I added a small benchmark for testing, remember to check both variants with the empty database.
$time1 = microtime(true);
// function start
if (!$manufacturer)
{
$manufacturer = new Manufacturer();
$manufacturer->setPosId($item->manufacturerID);
$this->em->persist($manufacturer);
$this->em->flush(); // only flush when there's a new manufacturer
}
// end of function
$time2 = microtime(true);
$time = $time2 - $time1;
printr("Time elapsed: $time");

Answer 2

Manufacturer m = new Manufacturer();
m.ManufacturerID = 123;
Database.Load(m);
m.Name = "abc";
Database.Store(m);
'much easier than symfony. Sim. Phony. J/k.