From: Daniel DeLorme <dan-ml@...42.com>
Date: 2006-08-04T09:03:32+09:00
Subject: Re: Array#size empties the Array??

Sven Suska wrote:
>> This may be irrelevant, but what's rks.class.ancestors?
> 
> [Array,
>  ActiveSupport::CoreExtensions::Array::Conversions,
>  Enumerable,
>  Object,
>  Kernel]

This is probably wrong. Try to do this instead:
   (class << rks;self;end).ancestors
and you'll probably find this:
   [ActiveRecord::Associations::HasManyAssociation, 
ActiveRecord::Associations::AssociationCollection, 
ActiveRecord::Associations::AssociationProxy, Object, Base64::Deprecated, 
Base64, Kernel]

ActiveRecord associations forward most messages (including 'class') to the 
underlying array structure, but some messages (like 'size') are part of the 
association class itself.

I think what's happening is that by calling 'size' first, the objects have not 
yet been fetched from the database so instead it uses a COUNT(*) query to find 
the size. When calling 'length' (or any other method) first, the objects are 
fetched from the database and placed in an array and the 'length' message is 
forwarded to that array. Then, when 'size' is invoked again, it notices that the 
array is already present and uses its size instead of wasting time doing another 
DB query. Normally the results should be the same but in your case something 
weird is happening. I don't know what exactly but this should give you some 
avenues to investigate.

Daniel