How to find a document by looking for a match in an embedded document array? - mongodb

Question

This seems so simple but apparently I'm missing something. I've got a WebSite model:
class WebSite
include Mongoid::Document
has_many :domains, inverse_of: :web_site
field :name, type: String
end
The WebSite model has an embedded array of Domains:
class Domain
include Mongoid::Document
belongs_to :web_site, inverse_of: :domains
field :name, type: String
end
All I'm trying to do is find a WebSite with a domain of "test.com". Nothing I've tried seems to work, either with Mongoid or with the MongoDB console. For example, if I have one WebSite, with one Domain, with the name "test.com":
2.0.0p0 :001 > WebSite.count
=> 1
2.0.0p0 :002 > WebSite.first.domains
=> [#<Domain _id: 5148d9b76a3b8b1fe6000003, web_site_id: "5148d9a96a3b8b1fe6000002", name: "test.com">]
...then shouldn't this work?
2.0.0p0 :003 > WebSite.elem_match(domains: { name: "test.com" }).count
=> 0
2.0.0p0 :004 > WebSite.elem_match('domains' => { 'name' => "test.com" }).count
=> 0
I get zero. I should get one.
I also got the impression from the O'Reilly book that this should work:
2.0.0p0 :005 > WebSite.where('domains.name' => "test.com").count
=> 0
...same with any_in:
.0.0p0 :006 > WebSite.any_in('domains' => { 'name' => "test.com" }).count
=> 0
I've also tried those same queries from the MongoDB console with the same results:
> db.web_sites.find({"domains" : {"$elemMatch" : {"name" : "test.com"}}}).size();
0
> db.web_sites.find({"domains.name" : "test.com"}).size();
0
> db.web_sites.find({"domains" : {$in : {"name" : "test.com"}}}).size();
0
I must be missing something?
Update:
Here is some more information about the schema, from the MongoDB console:
> db.web_sites.find().pretty()
{ "_id" : ObjectId("5148d9a96a3b8b1fe6000002"), "name" : "test" }

Answer 1

Thanks to uldall's help with debugging (that awesome pretty() technique) I realized that my problem was that I had two separate collections side by side, instead of a Domain collection embedded in my WebSite collection. This is how my models should have been set up, with "embedded_in" and "embeds_many":
class WebSite
include Mongoid::Document
embeds_many :domains, inverse_of: :web_site
field :name, type: String
end
class Domain
include Mongoid::Document
embedded_in :web_site, inverse_of: :domains
field :name, type: String
end
Now the document looks like this from the MongoDB console:
> db.web_sites.find().pretty()
{
"_id" : ObjectId("5148e63f6a3b8b8ffa000001"),
"domains" : [
{
"_id" : ObjectId("5148e6706a3b8b8ffa000002"),
"name" : "test.com"
}
],
"name" : "test"
}
With that schema, this works:
2.0.0p0 :008 > WebSite.where('domains.name' => 'test.com').count
=> 1
[CHEER]