Rails - Jun 2005 - Find by ID plus conditions -> ActiveRecord::RecordNotFound

Hi

I''m trying to understand the AR find facilities, described here:
http://api.rubyonrails.com/classes/ActiveRecord/Base.html#M000650

I have a list of ids that I want to retrieve, but have a condition that
should restrict the list returned:

return self.find(
  noteids,
  :conditions => [ "(private = 0 OR (private = 1 AND user_id =
?))", userid]
)

According to the documentation for find, I can supply this list of
noteids and a :conditions option. 

I can see in the developer log that this results in an SQL call like
this:

SELECT * FROM notes WHERE notes.id IN
(''17'',''36'',''39'',''54'')
AND (private = 0 OR (private = 1 AND user_id = 1)) ORDER BY id

But when the conditions supplied reduce the actual number of notes
returned (e.g. the note with id 54 is excluded) then I get an
ActiveRecord::RecordNotFound, which is raised in active_record/base.rb
line 356:

if result.size == ids.size
  return result
else
  raise RecordNotFound, "Couldn''t find all #{name.pluralize} with
IDs (#{ids_list})#{conditions}"
end

(I have active record version 1.10.1) 

The ability to supply a :conditions option in the find (by id) call
seems to conflict with the code above - any condition that would exclude
something with a given (supplied) id would cause this RecordNotFound
issue. 

It''s likely that it''s my misunderstanding, so I''d be
grateful for any
enlightenment please. 

Thanks!
DJ Adams

p.s. I''ve Googled in vain for this so far ...

On 6/30/05, DJ Adams <dj.adams-e+AXbWqSrlAAvxtiuMwx3w@public.gmane.org>
wrote:
> Hi
> 
> I''m trying to understand the AR find facilities, described here:
> http://api.rubyonrails.com/classes/ActiveRecord/Base.html#M000650
> 
> I have a list of ids that I want to retrieve, but have a condition that
> should restrict the list returned:
> 
> return self.find(
>   noteids,
>   :conditions => [ "(private = 0 OR (private = 1 AND user_id =
?))", userid]
> )
> 
> According to the documentation for find, I can supply this list of
> noteids and a :conditions option.
> 
> I can see in the developer log that this results in an SQL call like
> this:
> 
> SELECT * FROM notes WHERE notes.id IN
(''17'',''36'',''39'',''54'')
AND (private = 0 OR (private = 1 AND user_id = 1)) ORDER BY id
> 
> But when the conditions supplied reduce the actual number of notes
> returned (e.g. the note with id 54 is excluded) then I get an
> ActiveRecord::RecordNotFound, which is raised in active_record/base.rb
> line 356:
> 
> if result.size == ids.size
>   return result
> else
>   raise RecordNotFound, "Couldn''t find all #{name.pluralize}
with IDs (#{ids_list})#{conditions}"
> end
> 
> (I have active record version 1.10.1)
> 
> The ability to supply a :conditions option in the find (by id) call
> seems to conflict with the code above - any condition that would exclude
> something with a given (supplied) id would cause this RecordNotFound
> issue.
>From the API docs:
  Find operates with three different retreval approaches:
    * Find by id: This can either be a specific id (1), a list of ids (1, 5, 6),
       or an array of ids ([5, 6, 10]). If no record can be found for
all of the listed
       ids, then RecordNotFound will be raised.
    * Find first: This will return the first record matched by the options used.
       These options can either be specific conditions or merely an
order. If no
       record can matched, nil is returned.
    * Find all: This will return all the records matched by the options used. If
       no records are found, an empty array is returned.

Perhaps you should try
  return self.find(
    :all,
    noteids,
    :conditions => [ "(private = 0 OR (private = 1 AND user_id =
?))", userid]
  )

The if-statement you analized actually occurs within the else block of a 
case-statement. The second when-block (when :all on line 333) is what will be 
used if you try my example. You might also want to take a look at more 
examples in http://api.rubyonrails.com/

I hope this helps,

 - Rowan

-- 
Morality is usually taught by the immoral.

On Sat, Jul 02, 2005 at 12:04:58AM +0200, BigSmoke
wrote:
> >From the API docs:
> 
>   Find operates with three different retreval approaches:
>     * Find by id: This can either be a specific id (1), a list of ids (1,
5, 6),
>        or an array of ids ([5, 6, 10]). If no record can be found for
> all of the listed
>        ids, then RecordNotFound will be raised.
> [...]
Hi Rowan

Thanks for your response, it''s appreciated. I did read the API
documentation, and that''s what led me to ask the question. Basically it
boils down to:

"Why allow a condition on find-by-id and then raise an exception if
that condition does what you want - filtering the records found from
the list of IDs supplied?"

It just doesn''t make sense, unless you''re writing
exception-driven code
(which I don''t think is the case). 

In other words, I have a list of IDs that I want to pick from, and I
only want those that satisfy the condition. That seems a reasonable
thing to want to do. But trying that results in an exception. Using
the :all construct (which I did in the end, and which you showed as a
workaround) does do the job, but is ultimately more ''blunt''.

Thanks
DJ