How can I ask MongoDB to evaluate some JavaScript in order to obtain value for a field?

Question

I want to let MongoDB dynamically assign a value to one of the fields of the document I\'m inserting. For example: the current time from MongoDB server just like NOW() woul

Answer 1

See the following URL on the MongoDB documentation:

http://www.mongodb.org/display/DOCS/Server-side+Code+Execution#Server-sideCodeExecution-Storingfunctionsserverside

There is a special system collection called system.js that can store JavaScript functions to be reused.

Note though, that the support and performance of server-sided code (equivalent to stored procedures) is still a little poor (details in link).

Edit:

To call a stored procedure from Go using the mgo driver use the mgo.Database type's Run() method (direct link) and issue an eval command with the Javascript code to be executed server-side as argument. Something like:

db.Run(bson.M{"eval": "myStoredFunction();"})

_{code untested}

It is not possible to have code evaluated in a MongoDB insert statement.