Rails - Mar 2006 - ActiveRecord returning Strings with find_by_sql?

Hello,

I''m new to Ruby & Rails, and I''m trying to figure out if
this
behavior by ActiveRecord is by design, or if I''m doing something  
incorrectly. Here''s the deal: I have a class based on  
ActiveRecord::Base that defines a method that creates a query using  
find_by_sql(). The fields retrieved by joins with other tables are  
being returned as Strings, regardless of field type. Fields from the  
table that the class directly corresponds to are being returned as  
whatever type is appropriate. Is that how it''s supposed to work? I  
find myself having to do a lot of conversions when I need to perform  
any math on the results obtained from this query.

Thanks for your help,

Mike Marcus
Software Engineer
Broadband.com
mmarcus@broadband.com

Mike Marcus wrote:
> Hello,
>
> I''m new to Ruby & Rails, and I''m trying to figure out
if this behavior
> by ActiveRecord is by design, or if I''m doing something
incorrectly.
> Here''s the deal: I have a class based on ActiveRecord::Base that 
> defines a method that creates a query using find_by_sql(). The fields 
> retrieved by joins with other tables are being returned as Strings, 
> regardless of field type. Fields from the table that the class 
> directly corresponds to are being returned as whatever type is 
> appropriate. Is that how it''s supposed to work? I find myself
having
> to do a lot of conversions when I need to perform any math on the 
> results obtained from this query.
>
> Thanks for your help,
>
It''s a long known deficiency of the current ActiveRecord implementation
(http://dev.rubyonrails.org/ticket/240). Likely not to change very soon.

-- stefan

-- 
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Mike Marcus wrote:
> I''m new to Ruby & Rails, and I''m trying to figure out
if this  behavior
> by ActiveRecord is by design, or if I''m doing something 
incorrectly.
> Here''s the deal: I have a class based on  ActiveRecord::Base that 
> defines a method that creates a query using  find_by_sql(). The fields 
> retrieved by joins with other tables are  being returned as Strings, 
> regardless of field type. Fields from the  table that the class directly 
> corresponds to are being returned as  whatever type is appropriate. Is 
> that how it''s supposed to work? I  find myself having to do a lot
of
> conversions when I need to perform  any math on the results obtained 
> from this query.
That''s how it works. You only get automatic casting for fields in
the model on which find is called, and only for fields from joined
tables when you use find''s :include option.

You can however define custom reader and writer methods for the
joined fields so that you only have to write the casting code once.

-- 
We develop, watch us RoR, in numbers too big to ignore.

> That''s how it works. You only get automatic casting
> for fields in
> the model on which find is called, and only for
> fields from joined
> tables when you use find''s :include option.
Isn''t it database specific? Doesn''t oracle return type
information and isn''t that used to cast it? I use
mysql so they are always strings for me, but I believe
I read that it''s different for other db''s.

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Jay Donnell wrote:
>>That''s how it works. You only get automatic casting
>>for fields in
>>the model on which find is called, and only for
>>fields from joined
>>tables when you use find''s :include option.
> 
> Isn''t it database specific? Doesn''t oracle return type
> information and isn''t that used to cast it? I use
> mysql so they are always strings for me, but I believe
> I read that it''s different for other db''s.
You''re right. My reply was MySQL-centric.  p273 of
/Agile Web Development with Rails/ states that the
Oracle adaptor will type-convert all fields fetched
from the DB.

-- 
We develop, watch us RoR, in numbers too big to ignore.

Thanks, Mark and Stefan for your replies!

- Mike


On Mar 8, 2006, at 5:56 PM, Mark Reginald James wrote:
> Mike Marcus wrote:
>
>> I''m new to Ruby & Rails, and I''m trying to figure
out if this
>> behavior by ActiveRecord is by design, or if I''m doing
something
>> incorrectly. Here''s the deal: I have a class based on   
>> ActiveRecord::Base that defines a method that creates a query  
>> using  find_by_sql(). The fields retrieved by joins with other  
>> tables are  being returned as Strings, regardless of field type.  
>> Fields from the  table that the class directly corresponds to are  
>> being returned as  whatever type is appropriate. Is that how
it''s
>> supposed to work? I  find myself having to do a lot of conversions  
>> when I need to perform  any math on the results obtained from this  
>> query.
>
> That''s how it works. You only get automatic casting for fields in
> the model on which find is called, and only for fields from joined
> tables when you use find''s :include option.
>
> You can however define custom reader and writer methods for the
> joined fields so that you only have to write the casting code once.
>
> -- 
> We develop, watch us RoR, in numbers too big to ignore.
>
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