Hello and thanks for the feedback.
foca, thanks for the clarification. I did know about the differences
between .size and .count but I didn't remember about .length.
However, despite length returning the needed results (potentially with
an extra query), I find it misleading to have AR execute a COUNT query
on both .count and .size that ignores the current scope, deliberately
expressed by the developer.
In that regard, I think Jeremy is right appointed Sequel behavior is
more in line with what the average developer - like myself - would
expect AR to return.
I'm not too familiar with AR codebase, but I'll try and check how hard
it would be to modify .count and .size, making them take into account
the current scope.
Thanks,
DBA
On Aug 1, 12:05 am, Jeremy Evans <jeremyeva...@gmail.com> wrote:
> 2010/7/31 Nicolás Sanguinetti <h...@nicolassanguinetti.info>:
>
>
>
>
>
> > On Sat, Jul 31, 2010 at 6:08 PM, DBA <diogo.borges.alme...@gmail.com> wrote:
> >> I've implemented the following scope in a rails 3 application:
>
> >> scope :popular, lambda { |l = 5| order('views desc').limit(l) }
>
> >> However, it seems that when you attempt to count its records directly
> >> it doesn't apply the scope filters.
>
> >> For example:
>
> >> Post.popular.size #=> 20
>
> >> Checking the log, it executes the following query:
>
> >> SQL (0.4ms) SELECT COUNT(*) AS count_id FROM `posts` LIMIT 5
>
> >> Now if I execute
>
> >> Post.popular.all.size #=> 5
>
> >> And the correct query is executed:
>
> >> Post Load (1.5ms) SELECT `posts`.* FROM `posts` ORDER BY views
> >> desc LIMIT 5
>
> >> Anyone else experienced this kind of behavior? If so, any idea if this
> >> is the expected behavior or am I facing a bug?
>
> > This is expected. The three ways to get the size of an ActiveRecord
> > collection are:
>
> > .count #=> this always triggers a SELECT COUNT(*) on the database
> > .size #=> if the collection has been loaded, defers to
> > Enumerable#size, else does the SELECT COUNT(*)
> > .length #=> always loads the collection and then defers to
> > Enumerable#size (I think it's length, but I don't think I ever used it
> > :P)
>
> > So, since Post.popular doesn't trigger the query and load the objects,
> > calling size will do a count query.
>
> > This is, apparently, a good use case for Post.popular.length :)
>
> Or a good reason to change the code to do:
>
> SELECT COUNT(*) FROM (SELECT `posts`.* FROM `posts` ORDER BY views
> desc LIMIT 5) AS some_alias
>
> which is Sequel's behavior.
>
> Jeremy
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