Has been solved in SO

On Thursday, April 12, 2018 at 9:27:52 AM UTC-5, Jonathan Pham wrote:
> Posted SO question with code examples:
> https://stackoverflow.com/questions/49780731/how-does-drf-serialize-manytomany-fields
> Trying to optimize my serializer.
> DRF automatically renders a manytomany as a list of pks. Using the default 
> with prefetch_related takes only 2 queries.
> All I want to do is return an intersection of that list with the queried 
> pks.
> def get_failbin_regressions(self, obj):
>         runids = self.context.get('runids')
>         return obj.runs.values_list('id', flat=True)
> However when accessing the many to many in a serializermethodfield causes 
> a query for each row. Why is this? Is the prefetch lost in a 
> serializermethodfield?
> The end goal is to get a list with the same results as return obj.runs.
> values_list('id', flat=True).filter(id__in=runids)   without the extra 
> queries.
> Thanks!

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