On Saturday, July 7, 2012 3:43:48 PM UTC-6, Jeremy Evans wrote:
>
> On Saturday, July 7, 2012 2:09:43 PM UTC-7, Joe Van Dyk wrote:
>>
>> Given the following:
>>
>> buyable = DB[:product_listings].where(:buyable => true)
>>
>> recent = DB[:product_listings].where("start_sale_date > now() - interval
>> '1 day'")
>>
>> What's the best way to find all recent buyable products? (Ideally,
>> without using Sequel::Model)
>>
>> In AR, I'd do:
>>
>> class ProductListing
>> scope :buyable, where(:buyable => true)
>> scope :recent, where("start_sale_date > now() - interval '1 day'")
>> end
>> ProductListing.buyable.recent
>>
>
> You probably want to use subset:
>
> class ProductListing
> subset :buyable, :buyable => true
> subset :recent, "start_sale_date > now() - interval '1 day'"
> end
>
> or for more general things that aren't simple where conditions, either
> def_dataset_method:
>
> class ProductListing
> def_dataset_method(:buyable){where(:buyable => true)}
> def_dataset_method(:recent){where("start_sale_date > now() - interval '1
> day'")}
> end
>
> or dataset_module:
>
> class ProductListing
> dataset_module do
> def buyable; where(:buyable => true) end
> def recent; where("start_sale_date > now() - interval '1 day'") end
> end
> end
>
> All of those are for Sequel::Model though.
>
>
I was hoping to not use Sequel::Model. :)
> If you really want to get the intersection of products that are both
> buyable and recent taking the two separate datasets as input, you want an
> SQL INTERSECT query:
>
> DB[:product_listings].where(:buyable =>
> true).intersect(DB[:product_listings].where("start_sale_date > now() -
> interval '1 day'"))
>
>
I don't think that sort of intersection would be nearly as efficient as
combining the where clauses.
> However, it's rare to actually do that. In most cases you'd just add the
> appropriate buyable and recent filter conditions to the same dataset, where
> they would be ANDed together in the where clause:
>
> DB[:product_listings].where(:buyable => true).where("start_sale_date >
> now() - interval '1 day'")
>
Right, so what I was looking for is a way to combine these where clauses.
Maybe I want to do something sorta like:
def Decorate ds
def ds.with_recent
where("start_sale_date < now() - interval '1 month'")
end
def ds.with_buyable
where(:buyable => true)
end
ds
end
puts Decorate(DB[:product_listings]).with_buyable.with_recent.sql
Thoughts?
>
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