Generating Mongo ObjectId (_id) with custom time?

Question

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?

Answer 1

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 easiest to use the helper method GenerateNewId:

var id = ObjectId.GenerateNewId(new DateTime(2012, 01, 01));

I don't know which programming language you're using and whether the driver in that language supports this feature, but I guess this is widely available.

EDIT: This question contains the code for Java, mongoose and python, and the answer contains code for PHP. "Widely available" seems to be a wrong assumption, it's not yet implemented in the PHP driver, for instance.