Hi Adam,
I am using sequel version 4.36.0
In both the cases (using :items__id and Sequel.qualify(“items”, “id”)), I
am receiving " unknown column 'items.id' in 'where clause' ".
Same is the result when I use "Item.select_append { |p|
Review.where(item_id: p.items__id).avg(:rating) }"
Ref:
http://sequel.jeremyevans.net/rdoc/files/doc/virtual_rows_rdoc.html#label-SQL-3A-3AQualifiedIdentifiers+-+Qualified+columns
Thanks,
Satya
On Tuesday, June 27, 2017 at 8:42:15 PM UTC+5:30, Adam Daniels wrote:
>
> Likely my syntax (or your version of Sequel?), as I didn’t have a chance
> to confirm.
>
> You can try symbol splitting, or maybe Sequel.qualify
>
> Item.select_append { Review.where(item_id: :items__id).avg(:rating) }
>
> or
>
> Item.select_append { Review.where(item_id: Sequel.qualify(“items”,
> “id”)).avg(:rating) }
>
> I noticed I passed a singular version of the table name originally so it
> likely wouldn’t of worked anyways.
>
>
> On Jun 27, 2017, at 11:09 AM, Satyanarayana Gandham <
> [email protected] <javascript:>> wrote:
>
> Hi Adam,
>
> Thanks for the reply. Unfortunately, I am getting an error. '[]' is not
> defined for Sequel:Module.
>
> Regards,
> Satya
>
> On Monday, June 26, 2017 at 9:21:24 PM UTC+5:30, Adam Daniels wrote:
>>
>> 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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