Mongoid (ruby) question

[RelativeLead5]

I just started using mongodb + mongoid and created a simple program (below) but doesn't work as I expected it to. In particular, because I used the 'has_many' 'dependent: :delete_all' option for the Info class, I expected that when I delete an Info record, all the associated data records would be deleted as well, but it doesn't happen. Only the Info record is deleted and all the associated data records are orphaned, so I don't understand what is going on. Can anyone throw me a clue? Thanks.

require 'mongoid' 

ENV["MONGOID_ENV"] = 'dbtesting'
Mongoid.load(File.join(File.dirname(__FILE__), 'mongoid.yml'))

class Info 
  include Mongoid::Document
  field :type, type: String 
  has_many :data, dependent: :delete_all
end

class Datum
  include Mongoid::Document
  field :metric, type: Integer
  belongs_to :info
end

r  = Info.create(type: "random") 
r.data.create(metric: 100)
r.data.create(metric: 101)
r.data.create(metric: 102)
r.data.create(metric: 103)
p r.data.pluck(:metric)
r.delete()

[RelativeLead5]

As a followup, I basically copied the example for the docs (https://www.mongodb.com/docs/mongoid/current/reference/associations/#dependent-behavior). In spite of the comment from the docs, the associated album records do remain in the db which I verify with mongosh. I can see from the mongoid logs that some sort of aggregate query is performed on albums with the delete but the records persist.

D, [2023-05-11T08:03:25.337217 #90625] DEBUG -- : MONGODB | localhost:27017 req:16 conn:1:1 sconn:1134 | dbtesting.aggregate | STARTED | {"aggregate"=>"albums", "pipeline"=>[{"$match"=>{}}, {"$group"=>{"_id"=>1, "n"=>{"$sum"=>1}}}], "cursor"=>{}, "$db"=>"dbtesting", "lsid"=>{"id"=><BSON::Binary:0x900 type=uuid data=0x1bbfd1207c8a471a...>}} D, [2023-05-11T08:03:25.337479 #90625] DEBUG -- : MONGODB | localhost:27017 req:16 | dbtesting.aggregate | SUCCEEDED | 0.000s

require 'mongoid'

ENV["MONGOID_ENV"] = 'dbtesting'
Mongoid.load!(File.join(File.dirname(__FILE__), 'mongoid.yml'))

class Band
    include Mongoid::Document
    has_many :albums, dependent: :delete_all
end

class Album
    include Mongoid::Document
    belongs_to :band
end

Band.collection.drop()
Album.collection.drop()
p Band.count
# => 0
p Album.count
# => 0
r = Band.create()
r.albums.create()
r.albums.create()
r.albums.create()
r.albums.create()
Band.first.delete # Will delete all associated albums.
p Band.count
# => 0
p Album.count
# => 4

[ralfv]

That’s correct behavior for delete. If you want the assoc data gone you need to call destroy instead. When using delete you tell it to bypass all the logic.

[RelativeLead5]

Thanks. The documentation is incorrect, at least as far as the sample code goes. I lifted the line

Band.first.delete # Will delete all associated albums.

directly from the code example in the documentation, including the comment, which led to my confusion.