On 10/12/18 10:51 AM, charettes wrote:
Hello Tobias,

 From my understanding the introduction of chunk_size doest't help here.

The fundamental reason why iterator() cannot be used with prefetch_related() is that the latter requires a set of model instance to be materialized to work appropriately which chunk_size doesn't control at all.

In other words chunk_size only controls how many rows should be fetched from the database cursor and kept into memory at a time. Even when this parameter is used, iterator() will only materialize a single model instance per yield.

I inferred from the original post they were suggesting to do a set of prefetch_related "filling" queries _per_ _chunk_

It wouldn't be as efficient as the 1+P (where P is number of prefetched relations) of a normal prefetch_related, but at 1+(P x Chunks) it would _probably_ be more efficient than the 1+(P x N-rows) it would otherwise be [or worse!]

--
Curtis

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