Maybe it would be useful to implement `dataset.first` in terms of
`dataset.limit(1).all.first`, do you think there would any downsides to
this?
Cool, I didn't know that association calls can take blocks, this will
really come in handy.
On Wednesday, May 13, 2015 at 3:42:57 AM UTC+2, Jeremy Evans wrote:
>
> On Tuesday, May 12, 2015 at 4:42:46 PM UTC-7, Janko Marohnić wrote:
>>
>> A question related to this situation, which I'm not sure it's a bug.
>>
>> user = User.eager(:quizzes => :questions).all.first
>> user.associations #=> {:quizzes => [...]}
>>
>> user = User.eager(:quizzes => :questions).first
>> user.associations #=> {}
>>
>> So, when I fetch the first user directly, the eager loading is cancelled,
>> meaning that fetching questions for each quiz will result in a N+1 query.
>> However, doesn't Sequel have all the necessary information to do the eager
>> loading?
>>
>
> First, if you are loading a single record, there is no reason to use eager
> loading. Eager loading is only an advantage if you are loading multiple
> records. 1+1 = N+1 if N = 1.
>
> In terms of having the necessary information to eager load, not really.
> Dataset#first calls Dataset#each, which iterates over the recordset, and
> therefore doesn't have all records available before iterating, which is
> necessary to eager load correctly. If you want, you can use the eager_each
> plugin, which makes #each call #all internally if the dataset is supposed
> to eager load.
>
> So no, this isn't a bug, it is expected behavior.
>
> If you want to always eager load questions when loading quizzes for a
> given user:
>
> User.first.quizzes{|ds| ds.eager(:questions)}
> # or
> User.one_to_many :quizzes, :eager=>:questions
> User.first.quizzes # eager loads questions as well
>
> Thanks,
> Jeremy
>
--
You received this message because you are subscribed to the Google Groups
"sequel-talk" group.
To unsubscribe from this group and stop receiving emails from it, send an email
to [email protected].
To post to this group, send email to [email protected].
Visit this group at http://groups.google.com/group/sequel-talk.
For more options, visit https://groups.google.com/d/optout.
