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Giant Cranes

2007-Apr-12 20:03 UTC

Model.find(:all) - return a list of ids

Hi,

I currently call find(:all, ...) on one of my models and it return a
page of models.

I am now looking at adding a memcached server and want the find(:all..)
to only return model ids, the models will be individually retrieved from
the cache.

Is this something that ActiveRecord supports or should I write a custom
bit of sql?

Thanks,
GiantCranes

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Rick Olson

2007-Apr-12 20:33 UTC

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Re: Model.find(:all) - return a list of ids

On 4/12/07, Giant Cranes
<rails-mailing-list-ARtvInVfO7ksV2N9l4h3zg@public.gmane.org>
wrote:>
> Hi,
>
> I currently call find(:all, ...) on one of my models and it return a
> page of models.
>
> I am now looking at adding a memcached server and want the find(:all..)
> to only return model ids, the models will be individually retrieved from
> the cache.
>
> Is this something that ActiveRecord supports or should I write a custom
> bit of sql?
You''ll have to write a bit of SQL for this, since it''s not
really a
common operation.  You can use the #select_values method of the
connection object:

  Widget.connection.select_values("select id from widgets")

-- 
Rick Olson
http://lighthouseapp.com
http://weblog.techno-weenie.net
http://mephistoblog.com

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Giant Cranes

2007-Apr-12 20:35 UTC

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Re: Model.find(:all) - return a list of ids

Thanks Rick, I''ll do just that then.

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Ball, Donald A Jr \(Library\)

2007-Apr-12 20:42 UTC

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Re: Model.find(:all) - return a list of ids

> I currently call find(:all, ...) on one of my models and it 
> return a page of models.
> 
> I am now looking at adding a memcached server and want the 
> find(:all..) to only return model ids, the models will be 
> individually retrieved from the cache.
> 
> Is this something that ActiveRecord supports or should I 
> write a custom bit of sql?
You can do custom sql, or use the :select option to limit the columns
returned:

model.find(:all, :select=>''id'') returns an array of models
with only the
ids loaded

model.find(:all, :select=>''id'').collect(&:id) returns
an array of ids

if you like using the rest of the find options to help generate your sql
for you.

- donald

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Florian Gilcher

2007-Apr-12 20:49 UTC

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Re: Model.find(:all) - return a list of ids

> You can do custom sql, or use the :select option to limit the columns
> returned:
> 
> model.find(:all, :select=>''id'') returns an array of
models with only the
> ids loaded
> 
> model.find(:all, :select=>''id'').collect(&:id)
returns an array of ids
> 
> if you like using the rest of the find options to help generate your sql
> for you.
> 
> - donald
Sure, it does. But it creates an Object for each model, while raw SQL
gives you an Array of ids. From a performance perspective, the second
method is much better.

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Giant Cranes

2007-Apr-12 20:55 UTC

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Re: Model.find(:all) - return a list of ids

>> You can do custom sql, or use the :select option to limit the columns
>> returned:
>> 
>> model.find(:all, :select=>''id'') returns an array
of models with only the
>> ids loaded
>> 
>> model.find(:all, :select=>''id'').collect(&:id)
returns an array of ids
>> 
>> if you like using the rest of the find options to help generate your
sql
>> for you.
>> 
>> - donald
> 
> Sure, it does. But it creates an Object for each model, while raw SQL
> gives you an Array of ids. From a performance perspective, the second
> method is much better.
Thanks for the option donald, I hadn''t seen :select before.

I think I will go with the raw SQL option as this is an area of my 
application that will be under load.

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Michael Wang

2007-Apr-13 04:11 UTC

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Re: Model.find(:all) - return a list of ids

Giant Cranes wrote:> Hi,
> 
> I currently call find(:all, ...) on one of my models and it return a
> page of models.
> 
> I am now looking at adding a memcached server and want the find(:all..)
> to only return model ids, the models will be individually retrieved from
> the cache.
> 
> Is this something that ActiveRecord supports or should I write a custom
> bit of sql?
> 
> Thanks,
> GiantCranes
> 
ids = Model.find(:all, :select => "id")


-- 
Michael Wang

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Rails - Apr 2007 - Model.find(:all) - return a list of ids

Model.find(:all) - return a list of ids

Re: Model.find(:all) - return a list of ids

Re: Model.find(:all) - return a list of ids

Re: Model.find(:all) - return a list of ids

Re: Model.find(:all) - return a list of ids

Re: Model.find(:all) - return a list of ids

Re: Model.find(:all) - return a list of ids