Following this documentation page http://doctrine-orm.readthedocs.org/en/2.0.x/reference/batch-processing.html#iterating-large-results-for-data-processing I tried to create a batch process on 75k entities. But an error came in the ObjectHydrator on line 511 there's an Undefined offset. Now, i just use the SimpleObjectHydrator and it solve the problem. but i'm wondering if it's a real bug or just a miss use of Doctrine.
Reproduce this error could be hard so ask if you want me to give you more informations about it.