Question

So I have an embedded document that tracks group memberships. Each embedded document has an ID pointing to the group in another collection, a start date, and an optional expire date.

I want to query for current members of a group. “Current” means the start time is less than the current time, and the expire time is greater than the current time OR null.

This conditional query is totally blocking me up. I could do it by running two queries and merging the results, but that seems ugly and requires loading in all results at once. Or I could default the expire time to some arbitrary date in the far future, but that seems even uglier and potentially brittle. In SQL I’d just express it with “(expires >= Now()) OR (expires IS NULL)” — but I don’t know how to do that in Mongo.

Any ideas? Thanks very much in advance.

Answer 1

Just thought I’d update in-case anyone stumbles across this page in the future. As of 1.5.3, mongo now supports a real $or operator: http://www.mongodb.org/display/DOCS/Advanced+Queries#AdvancedQueries-%24or

Your query of “(expires >= Now()) OR (expires IS NULL)” can now be rendered as:

{$or: [{expires: {$gte: new Date()}}, {expires: null}]}