I have a method that calls Model.find(:first, :order => "RAND()") twice. I want it to return two different results but it always returns the same thing twice. Is there some kind of sql caching at work here? If so, can I disable for this method? thanks! Jason
First of all, I''m assuming you are calling rand() (lowercase). rand() returns a value less than between 0 and 1. Using this as the call to :order tells the database to use the column reference (rather than a name). In MySQL, if you pass a non-integer column value, it gets ignored. (Not sure how other databases handle it). I don''t really understand what you are trying to randomize in your order parameter. You should probably get the count of the records in your table and generate a random number between 1 and that count. Then use offset to select that record. On May 23, 10:35 am, jg <jgagn...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:> I have a method that calls Model.find(:first, :order => "RAND()") > twice. I want it to return two different results but it always returns > the same thing twice. Is there some kind of sql caching at work here? > If so, can I disable for this method? > > thanks! > > Jason
On Sat, May 23, 2009 at 10:06 PM, E. Litwin <elitwin-ur4TIblo6goN+BqQ9rBEUg@public.gmane.org> wrote: Speaking strictly from a MySQL perspective --> First of all, I''m assuming you are calling rand() (lowercase).Case isn''t significant.> I don''t really understand what you are trying to randomize in your > order parameter. > You should probably get the count of the records in your table and > generate a random number between 1 and that count. Then use offset to? The syntax below works just fine to return a random instance of Model.>> I have a method that calls Model.find(:first, :order => "RAND()") >> twice. I want it to return two different results but it always returns >> the same thing twice.What it *doesn''t* do is guarantee that any two randomly selected instances won''t be the same :-) Quick example:>> (1..20).each do?> @up = UserProfile.find(:first, :order => "rand()")>> puts @up.id >> end8 8 11 1 5 1 13 13 2 6 17 5 4 9 6 17 8 10 7 5 => 1..20 If the two really need to be different, you''ll have to address that with application logic. FWIW, -- Hassan Schroeder ------------------------ hassan.schroeder-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org
You may be getting stuck in the query cache. Try this:
Model.uncached { Model.find(:first, :order => "RAND()") }
Which will shut off query caching for that call.
--Matt Jones
On May 23, 1:35 pm, jg <jgagn...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
wrote:> I have a method that calls Model.find(:first, :order =>
"RAND()")
> twice. I want it to return two different results but it always returns
> the same thing twice. Is there some kind of sql caching at work here?
> If so, can I disable for this method?
>
> thanks!
>
> Jason
My bad - I didn''t notice the quotes around "rand()" in the first post. I thought a random number was being passed to the database rather than a function. On May 24, 8:10 am, Hassan Schroeder <hassan.schroe...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org> wrote:> On Sat, May 23, 2009 at 10:06 PM, E. Litwin <elit...-ur4TIblo6goN+BqQ9rBEUg@public.gmane.org> wrote: > > Speaking strictly from a MySQL perspective -- > > > First of all, I''m assuming you are calling rand() (lowercase). > > Case isn''t significant. > > > I don''t really understand what you are trying to randomize in your > > order parameter. > > You should probably get the count of the records in your table and > > generate a random number between 1 and that count. Then use offset to > > ? The syntax below works just fine to return a random instance of > Model. > > >> I have a method that calls Model.find(:first, :order => "RAND()") > >> twice. I want it to return two different results but it always returns > >> the same thing twice. > > What it *doesn''t* do is guarantee that any two randomly selected > instances won''t be the same :-) > > Quick example:>> (1..20).each do > > ?> @up = UserProfile.find(:first, :order => "rand()")>> puts @up.id > >> end > > 8 > 8 > 11 > 1 > 5 > 1 > 13 > 13 > 2 > 6 > 17 > 5 > 4 > 9 > 6 > 17 > 8 > 10 > 7 > 5 > => 1..20 > > If the two really need to be different, you''ll have to address that with > application logic. > > FWIW, > -- > Hassan Schroeder ------------------------ hassan.schroe...-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org