can not save new record to my rails model using mongoid and MongoDB

Question

Haven't change my code for some time, and it was working fine. But started yesterday, I found I can't save my new record to the mongod db via mongoid.

Background:

gem 'rails', '3.2.5'
gem 'mongo', "1.6.2"
gem "mongoid", "2.4.7"

mongo server version: db version v2.0.5, pdfile version 4.5 MongoDB shell version: 2.0.5

rails models and data size (still in development mode): 3 models (users: 164K, relation: 122M, status:370K)

Problem: Can't save new users records, as showing here, even it passed the contraints (like I have unique uid, id_str).

[2] pry(main)> User.count
=> 164325
[3] pry(main)> u=User.new(uid: 1001, id_str: "1001")
=> #<User _id: 501452f346b0a14fb5000001, _type: nil, created_at: nil, updated_at: nil, uid: 1001, id_str: "1001", name: nil, screen_name: nil, location: nil>
[4] pry(main)> u.save
=> true
[5] pry(main)> User.count
=> 164325
[6] pry(main)> u.save!
=> true
[7] pry(main)> User.count
=> 164325

Rails log file:

MONGODB (0ms) blog_development['$cmd'].find({"count"=>"users", "query"=>{}, "fields"=>nil}).limit(-1)
MONGODB (0ms) blog_development['users'].insert([{"_id"=>BSON::ObjectId('501452f346b0a14fb5000001'), "uid"=>1001, "id_str"=>"1001", "updated_at"=>2012-07-28 21:00:39 UTC, "created_at"=>2012-07-28 21:00:39 UTC}])
MONGODB (0ms) blog_development['$cmd'].find({"count"=>"users", "query"=>{}, "fields"=>nil}).limit(-1)
MONGODB (0ms) blog_development['$cmd'].find({"count"=>"users", "query"=>{}, "fields"=>nil}).limit(-1)

Nothing in the mongodb.log file as the operation is so fast

What could be the reason causing the not-saving issue?

updates: My db status in mongo shell:

"ns" : "blog_development.users",
    "count" : 164325,
    "size" : 159656080,
    "avgObjSize" : 971.5872813022972,
    "storageSize" : 177336320,
    "numExtents" : 14,
    "nindexes" : 3,
    "lastExtentSize" : 36089856,
    "paddingFactor" : 1.0099999999963194,
    "flags" : 1,
    "totalIndexSize" : 22729280,
    "indexSizes" : {
        "_id_" : 9598624,
        "uid_1" : 6091120,
        "screen_name_1" : 7039536
    },
    "ok" : 1

os is: 2.6.38-8-generic #42-Ubuntu SMP Mon Apr 11 03:31:24 UTC 2011 x86_64 x86_64 x86_64 GNU/Linux

What does the DB shell output of db.users.stats() look like? and what O/S are you using? — Stennie
– Stennie, Commented Jul 28, 2012 at 21:56
just give a try using create, is it able to save to db. I was not able to get the soln :( — Bijendra
– Bijendra, Commented Jul 29, 2012 at 11:16

Stennie · Accepted Answer · 2012-08-02 03:03:34Z

4

You are using the save method which follows "upsert" semantics. If there is an existing document that can be found matching your criteria ((uid: 1001, id_str: "1001")), it will be updated instead of inserting a new document.

 u=User.new(uid: 1001, id_str: "1001")

 u.save
=> true

Since you actually intended to create a new document, you should be using insert:

u.insert

Alternatively, you can also allow a custom _id in your class and specify this on creation. You'll need to override Mongoid's _id field which is readonly by default.

answered Aug 2, 2012 at 3:03

Stennie

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1 Comment

Guoqiang Huang Over a year ago

Actually, there were a duplicated record in my database, find out that later. so you were right. Should distinguish "save" and "insert". Thanks.

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