MongoDb timestamp

Question

i have created and want to now import a dummy collection. one of the fields in each item are "created" and "updated" fields. what can i put in the source/json file so that MongoDb will use the current date and time as the value on import?

this wont work

"created" : Date()

i get a failure parsing JSON string error when i try "new Date()" — Simba, Oct 11 '12 at 00:08
you have to give as bit more information of what exactly you are doing. Can you post an excerpt of the json file and how you import it and may be what the exact error is. — peshkira, Oct 11 '12 at 09:51

score 14 · Accepted Answer · answered Oct 11 '12 at 13:20

mongoimport is intended for importing data existing data in CSV, TSV, or JSON format. If you want to insert new fields (such as a created timestamp) you will have to set a value for them.

For example, if you want to set the created timestamp to the current time, you could get a unix timestamp from the command line (which will be seconds since the epoch):

$ date +%s
1349960286

The JSON <date> representation that mongoimport expects is a 64-bit signed integer representing milliseconds since the epoch. You'll need to multiply the unixtime seconds value by 1000 and include in your JSON file:

{ "created": Date(1349960286000) }

An alternative approach would be to add the created timestamps to documents after they have been inserted.

For example:

db.mycoll.update(
    {created: { $exists : false }},    // Query criteria
    { $set : { created: new Date() }}, // Add 'created' timestamp
    false, // upsert
    true   // update all matching documents
)

What about if the field is an ISODate? I have noticed that the Date(timestamp) produces a string, and ISODate(sametimestamp) produces a completely different and unexpected date. How to convert from the string to the ISODate format ? — Ketema, Dec 18 '12 at 23:22
The [`ISODate()` function](https://github.com/mongodb/mongo/blob/v2.2/src/mongo/shell/utils.js#L400) is a convenient helper to create `Date()` objects. The `ISODate()` constructor expects an ISO8601-style date/time string, while `Date()` expects a unixtime (seconds since the epoch). If you try `new Date()` and `new ISODate()` in the `mongo` shell you should see they both produce the same value (an `ISODate`). Both formats have the same [BSON representation](http://bsonspec.org/#/specification), which is a UTC datetime. — Stennie, Dec 19 '12 at 20:20

score 3 · Answer 2 · answered Oct 25 '13 at 09:08

As Stennie correctly pointed out, you can not do this with just mongoimport or mongorestore: they are just for restoring your previously dumped data. Correct way of doing this is to restore the data and then to make update on the restored data.

With a new mongo 2.6 you can do this easily using $currentDate operation, which was created to update time to a current timestamp.

In your case you need something like

db.users.update( 
  {},
  {
     $currentDate: {
      created: true,
      updated: true
     },
  }
)

MongoDb timestamp

2 Answers2

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