Rails - Jun 2006 - Performance vs normalization best practice

I have a common situation and would like best practice suggestions from some
of you more experienced rails developers.
 
In my DB I''ve normalized tables in a traditional manner, e.g. I have
Posts
which have authors stored in a Users table.  
 
My problem is when I go to show a list of Posts and I want to display the
author name (e.g. post.author.name) 
ActiveRecord appears to do a SELECT on the Users table for each post.  If I
want to display additional author properties
(e.g. phone_number), additional queries are generated.  Clearly this is a
performance penalty for my normalization.
 
What''s the recommended way for avoiding the performance penalty WITHOUT
de-normalizing?  
 
In C# or Java I''d cache the "static" User data and do
in-memory lookups, but
in Rails I''m not sure how I''d set up such a cache
even if that were the right solution.
 
Thanks in advance.
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You could try:

  Post.find(:all, :include => :author)

This is on p244 of "Agile Web Development with Rails", which mentions 
that this will only work for databases which support LEFT OUTER JOIN. It 
is designed to avoid just the situation you are having by preloading the 
child rows.

Julian

-- 
Posted via http://www.ruby-forum.com/.

Scott R Brittain wrote:
> I have a common situation and would like best practice suggestions 
> from some of you more experienced rails developers.
>  
> In my DB I''ve normalized tables in a traditional manner, e.g. I
have
> Posts which have authors stored in a Users table. 
>  
> My problem is when I go to show a list of Posts and I want to display 
> the author name (e.g. post.author.name )
> ActiveRecord appears to do a SELECT on the Users table for each post 
> .  If I want to display additional  author properties
> (e.g. phone_number ), additional queries are generated.  Clearly this 
> is a performance penalty for my normalization.
>  
> What''s the recommended way for avoiding the performance penalty 
> WITHOUT de-normalizing?
My piggy back plugin seems to address this issue.

See http://railsexpress.de/blog/articles/2006/05/29/simpler-piggy-backing.

-- stefan

-- 
Rails performance tuning: http://railsexpress.de/blog
Subscription: http://railsexpress.de/blog/xml/rss20/feed.xml

On 6/24/06, Julian Gall <julian.gall@gmail.com>
wrote:
> You could try:
>
>   Post.find(:all, :include => :author)
>
> This is on p244 of "Agile Web Development with Rails", which
mentions
> that this will only work for databases which support LEFT OUTER JOIN. It
> is designed to avoid just the situation you are having by preloading the
> child rows.
>
> Julian
This is called ''eager loading'' if you''d like to
google for more information.


Isak