Question

I’ve been having this problem that I just can’t wrap my mind around. I need to get a sum the attribute “views” in my object, however, when using :include, I get a very innacurate sum.

>> c = Category.find 181
>> c.pages.sum(:views, :include => [:tags, :author], :conditions => q)
=> 48448

If I remove the :include, I get the correct sum.

>> c.pages.sum(:views, :conditions => q)
=> 11991

The amount of pages is the same in both queries, so I have no idea why that value could be any different. Going through each page will work as well.

>> c.pages.find(:all, :include => [:tags, :author], :conditions => q).each {|p| a += p.views}; a
=> 11991

:tags and :author do not have a :views attribute or even anything remotely similar, and even specifying the attribute with pages.views yields the same result.

Unfortunately, I need to get that value through the database in order to quickly generate a graph for the views. The q variable used in the conditions is the filter, and the reason the :include is needed. I don’t understand what could be causing this or where that 48448 value is coming from;

I’d appreciate any help in this, and thanks in advance.

Answer 1

Assume situation

pages
id|name    |views
1 |my_page |10

tags
id|name   |page_id
1 |my_tag1|1
2 |my_tag2|1

using

:include => [:tags]

you are duplicating page with id=1 two times:

result
pages.id|pages.name|pages.views|tags.id|tags.name|tags.page_id
1       |my_page   |10         |1      |my_tag1  |1
1       |my_page   |10         |2      |my_tag2  |1

Sum on column pages.views for this result set is 20 not 10.

[Edited]

Rewritten query witout using :include

c.pages.sum(:views, :conditions => ["id in (select distinct tags.page_id from tags where tags.id in (?))", tag_ids]