Rails - Jun 2006 - :limit => Parent / Child Relationship

Hi all,

I trying to find the best way to do the following and I''ll use a blog 
with comments for an example.

Blog has many comments
Comments belongs to blog

My question is how to limit the number of comments (child) records read 
for each blog (parent) record.  Most of the solutions I''ve come up with
are limiting the number of records displayed within the views but the 
select statement on the comments table still gets all of them.  My goal 
is to only show the 10 most recent comments for the blog entry if there 
are X + 10 comments, but I still want to be able to display all comments 
if the user chooses to.  I want to retrieve the least amount of records 
possible to save on performance.

I''m stumped on where to implement this.  In the model?  The controller?
And still make it DRY enough.

Any thoughts would be greatly appreciated.

Sam

try using limit in the has_many method call

has_many :comments
has_many :recent_comments, :class_name => "comment", :order =>
"created_at
DESC", :limit => 10

Then in your controller / view / whatever

@my_blog.recent_comments # => returns a result of the 10 (or upto 10 ) most
recent comments


On 6/24/06, Sam Schroeder <sschroeder@mn.rr.com>
wrote:
>
> Hi all,
>
> I trying to find the best way to do the following and I''ll use a
blog
> with comments for an example.
>
> Blog has many comments
> Comments belongs to blog
>
> My question is how to limit the number of comments (child) records read
> for each blog (parent) record.  Most of the solutions I''ve come up
with
> are limiting the number of records displayed within the views but the
> select statement on the comments table still gets all of them.  My goal
> is to only show the 10 most recent comments for the blog entry if there
> are X + 10 comments, but I still want to be able to display all comments
> if the user chooses to.  I want to retrieve the least amount of records
> possible to save on performance.
>
> I''m stumped on where to implement this.  In the model?  The
controller?
> And still make it DRY enough.
>
> Any thoughts would be greatly appreciated.
>
> Sam
>
>
> _______________________________________________
> Rails mailing list
> Rails@lists.rubyonrails.org
> http://lists.rubyonrails.org/mailman/listinfo/rails
>
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Daniel,

Thanks! That worked like a charm.  The only change I had to make was to 
capitalize the :class_name string.

Sam

Daniel N wrote:
> try using limit in the has_many method call
>
> has_many :comments
> has_many :recent_comments, :class_name => "comment", :order
=>
> "created_at DESC", :limit => 10
>
> Then in your controller / view / whatever
>
> @my_blog.recent_comments # => returns a result of the 10 (or upto 10 ) 
> most recent comments
>
>
> On 6/24/06, *Sam Schroeder* < sschroeder@mn.rr.com 
> <mailto:sschroeder@mn.rr.com>> wrote:
>
>     Hi all,
>
>     I trying to find the best way to do the following and I''ll use
a blog
>     with comments for an example.
>
>     Blog has many comments
>     Comments belongs to blog
>
>     My question is how to limit the number of comments (child) records
>     read
>     for each blog (parent) record.  Most of the solutions I''ve
come up
>     with
>     are limiting the number of records displayed within the views but the
>     select statement on the comments table still gets all of them.  My
>     goal
>     is to only show the 10 most recent comments for the blog entry if
>     there
>     are X + 10 comments, but I still want to be able to display all
>     comments
>     if the user chooses to.  I want to retrieve the least amount of
>     records
>     possible to save on performance.
>
>     I''m stumped on where to implement this.  In the model?  The
>     controller?
>     And still make it DRY enough.
>
>     Any thoughts would be greatly appreciated.
>
>     Sam
>
>
>     _______________________________________________
>     Rails mailing list
>     Rails@lists.rubyonrails.org <mailto:Rails@lists.rubyonrails.org>
>     http://lists.rubyonrails.org/mailman/listinfo/rails
>
>
>------------------------------------------------------------------------
>
>_______________________________________________
>Rails mailing list
>Rails@lists.rubyonrails.org
>http://lists.rubyonrails.org/mailman/listinfo/rails
>  
>
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