Re: [Rails] Problem with named_scope using a count
Dave Aronson
> I have two models, Post and Rate. You can rate each post with "good" or
> "bad".
> I would like to create a named_scope to get the best posts.
> How can I do that?
First you need to define "best". What is the overall rating for each
post? Good minus bad? Total good and ignore the bad? Something more
complex? How many "best" do you want?
Once you've defined that, you can figure out how to do it
programmatically for each post. Offhand I'd say this might wind up
being too slow to do on the fly for all posts, so as to find the top.
Premature optimization is the root of all evil, but still I'd give
SOME thought to how to stash a post's overall rating, especially in a
way that will make it trivial to retrieve the top N "best" posts (or
"worst" for that matter). Further thoughts if you like....
-Dave
--
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Greg Ma
> On Sat, Jul 24, 2010 at 13:23, Greg Ma <li...@ruby-forum.com> wrote:
>
>> I have two models, Post and Rate. You can rate each post with "good" or
>> "bad".
>> I would like to create a named_scope to get the best posts.
>> How can I do that?
>
> First you need to define "best". What is the overall rating for each
> post? Good minus bad? Total good and ignore the bad? Something more
> complex? How many "best" do you want?
>
> Once you've defined that, you can figure out how to do it
> programmatically for each post. Offhand I'd say this might wind up
> being too slow to do on the fly for all posts, so as to find the top.
> Premature optimization is the root of all evil, but still I'd give
> SOME thought to how to stash a post's overall rating, especially in a
> way that will make it trivial to retrieve the top N "best" posts (or
> "worst" for that matter). Further thoughts if you like....
>
> -Dave
Sorry I haven't been very clear.
The model Rate has a column kind where it is stored "good" or "bad".
What I want is to count all the "good" and "bast" rates.
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Posted via http://www.ruby-forum.com/.
pepe
When somebody rates the Post you just add 1 to whichever column you
need. Then it would be a simple matter of sorting your posts in
ascending/descending sequence by the column you want to work with.
I would add indexes by the columns to make it work faster.
Greg Ma
> Maybe adding 2 integer columns to your Posts table to count the hits?
>
> When somebody rates the Post you just add 1 to whichever column you
> need. Then it would be a simple matter of sorting your posts in
> ascending/descending sequence by the column you want to work with.
>
> I would add indexes by the columns to make it work faster.
Good idea
Dave Aronson
> Maybe adding 2 integer columns to your Posts table to count the hits?
>
> When somebody rates the Post you just add 1 to whichever column you
> need. Then it would be a simple matter of sorting your posts in
> ascending/descending sequence by the column you want to work with.
>
> I would add indexes by the columns to make it work faster.
That's pretty much what I had in mind for stashing. There is some
merit to still having a separate Rate model, storing *who* rated each
Post as good or bad (and maybe when?), to prevent ballot-stuffing and
let them change it later. However, I would be tempted to call it
Rating, since the noun Rate is how often something happens, not an
opinon.
pepe
> merit to still having a separate Rate model, storing *who* rated each
> Post as good or bad (and maybe when?), to prevent ballot-stuffing and
> let them change it later. However, I would be tempted to call it
> Rating, since the noun Rate is how often something happens, not an
> opinon.
stuffing you would have to come up with logic to stop it. First you
would need to be able to uniquely identify a user/visitor/rater and
then figure out some logic to stop the ballot-stuffing depending on
your needs (one vote only, or one vote per day/hour/week, etc).