objectid

In my database I have to store an array of object ids. What should I use? Something like this: [ObjectId("50350e12a36feb1be6000364"), ObjectId("57350e12a37fef1be6000922"), ObjectId("10350e17d34ffb1be6200925")] or something like this: ["50350e12a36feb1be6000364", "57350e12a37fef1be6000922", "10350e17d34ffb1be6200925"] I could save space with the second, and then cast to ObjectId , but am I loosing anything by using this approach? Do ObjectId s behave like foreign keys in relational databases? I would definitely go with the first approach, storing the ObjectId s directly. This saves space, as

I am porting over a table of articles from MySQL to Mongo DB. I understand that the _id field generated by Mongo has the time of creation somehow in there and can be extracted or you can query against it. Because of this, I want to use it to have my created_time INT timestamp from MySQL. Is there a way when moving my data to generate an _id for Mongo that will have the time stamp that I currently have for my records in a separate field? mnemosyn Yes, that's possible. In the C# driver for instance, there's a constructor for ObjectId where you can pass in a timestamp, see this source file . It's

I have a document in MongoDB and I would like to get the ObjectId of this document, but I did not find so far a method that does this to me. Example of query : user= db.users.find({userName:"Andressa"}) This returns this : { "_id" : ObjectId("53b1c579bdf3de74f76bdac9"), "userid" : 0, "userName" : "Andressa", "userEmail" : "dessa_beca@hotmail.com", "teams" : [ 1, 2, 3 ] } I want get the ObjectId to do another query . Example: userID = `user._id();` //but this does not work, of course, its an example So, I could user the ObjectId to do another query like this: userFind = db.users.find({_id:

I came across this ruby object_id allocation question sometime back and then read this awesome article which talks about VALUE and explains why object_id of true, nil and false the way they are. I have been toying with ruby2.0 object_id when I found the apparent change that has been made regarding object_id of true and nil. forbidden:~$ ruby -v ruby 2.0.0p0 (2013-02-24 revision 39474) [x86_64-linux] forbidden:~$ forbidden:~$ irb irb(main):001:0> true.object_id => 20 irb(main):002:0> false.object_id => 0 irb(main):003:0> nil.object_id => 8 irb(main):004:0> exit forbidden:~$ forbidden:~$ rvm use

Is it somehow possible to get the object id programmatically, which is seen in the debug tooltip in eclipse? moeTi This is an internal ID from the eclipse debugger and has nothing to do with the JVM. You can check this question for more information and a possible way to retrieve it. 来源： https://stackoverflow.com/questions/12578608/how-to-get-eclipse-debug-id-of-an-object

I have two collections User { "_id" : ObjectId("584aac38686860d502929b8b"), "name" : "John" } Role { "_id" : ObjectId("584aaca6686860d502929b8d"), "role" : "Admin", "userId" : "584aac38686860d502929b8b" } I want to join these collection based on the userId (in role collection) - _id ( in user collection). I tried the below query: db.role.aggregate( { $lookup: { from: 'user', localField: 'userId', foreignField: '_id', as: 'output' } } ); This gives me expected results as long as i store userId as a ObjectId. When my userId is a string there are no results. Ps: I tried foreignField: '_id'