I believe you can use `select_append` with a subquery to return a column
representing the average rating.
Something like:
Item.select_append { Review.where(item_id: Sequel[:item][:id]).avg(:rating)
}
You’ll have to access this field using the Array-style accessor, as it won’t
exist as a method on the Item instances.
> On Jun 26, 2017, at 10:41 AM, Satyanarayana Gandham
> <[email protected]> wrote:
>
> Hi,
>
> I have two models Item and Review. Item has one_to_many association with
> Review. Review has rating column which stores integers from 1 to 10. Rating
> of an item equals avg of the rating column in item's reviews_dataset.
>
> When I list the items, I want to list the rating as well. But the issues here
> is that I am calling DB 'N' no. of times for each item. Basically a N + 1
> problem. I have used eager loading for the associations to solve the N +1
> issue for the associations. But, the average here is not an association. Is
> there a way I can use eager functionality (or some other way) to load the
> average of a column in the associated dataset and not face the N +1 issue.
>
> Thanks,
> Satya
>
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