MongoDB query with an 'or' condition

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.

user_6883436 · Answer

MongoDB query with an 'or' condition

db.getCollection('movie').find({$or:[{"type":"smartreply"},{"category":"small_talk"}]})

MongoDB query with an 'or', 'and', condition combined.

db.getCollection('movie').find({"applicationId":"2b5958d9629026491c30b42f2d5256fa8",$or:[{"type":"smartreply"},{"category":"small_talk"}]})

user_104887 · Answer

Query objects in Mongo by default AND expressions together. Mongo currently does not include an OR operator for such queries, however there are ways to express such queries.

Use "in" or "where".

Its gonna be something like this:

db.mycollection.find( { $where : function() { 
return ( this.startTime < Now() && this.expireTime > Now() || this.expireTime == null ); } } );

user_4294682 · Answer

db.Lead.find(

{"name": {'$regex' : '.*' + "Ravi" + '.*'}},
{
"$or": [{
    'added_by':"arunkrishna@aarux.com"
}, {
    'added_by':"aruna@aarux.com"
}]
}

);

user_255357 · Answer

Using a $where query will be slow, in part because it can't use indexes. For this sort of problem, I think it would be better to store a high value for the "expires" field that will naturally always be greater than Now(). You can either store a very high date millions of years in the future, or use a separate type to indicate never. The cross-type sort order is defined at here.

An empty Regex or MaxKey (if you language supports it) are both good choices.

MongoDB query with an 'or' condition

6 Answers