mongodb - Find all documents within last n days

Question

My daily collection has documents like:

..
{ "date" : ISODate("2013-01-03T00:00:00Z"), "vid" : "ED", "san" : 7046.25, "izm" : 1243.96 }
{ "date" : ISODate("2013-01-03T00:00:00Z"), "vid" : "UA", "san" : 0, "izm" : 0 }
{ "date" : ISODate("2013-01-03T00:00:00Z"), "vid" : "PAL", "san" : 0, "izm" : 169.9 }
{ "date" : ISODate("2013-01-03T00:00:00Z"), "vid" : "PAL", "san" : 0, "izm" : 0 }
{ "date" : ISODate("2013-01-03T00:00:00Z"), "vid" : "CTA_TR", "san" : 0, "izm" : 0 }
{ "date" : ISODate("2013-01-04T00:00:00Z"), "vid" : "CAD", "san" : 0, "izm" : 169.9 }
{ "date" : ISODate("2013-01-04T00:00:00Z"), "vid" : "INT", "san" : 0, "izm" : 169.9 }
...

I left off _id field to spare the space here. My task is to "fetch all documents within last 15 days". As you can see I need somehow to:

1. Get 15 unique dates. The newest one should be takes as the newest document in collection (what I mean that it isn't necessary the today's date, it's just the latest one in collection based on date field), and the oldest.. well, maybe it's not necessary to strictly define the oldest day in query, what I need is some kind of top15 starting from the newest day, if you know what I mean. Like 15 unique days.
2. db.daily.find() all documents, that have date field in that range of 15 days.

So, in result, I should see all documents within 15 days starting from the newest in collection.

How do I do that?

Thank you

Answer 1

I just tested the following query against your data sample and it worked perfectly:

db.datecol.find(
{
    "date": 
    {
        $gte: new Date((new Date().getTime() - (15 * 24 * 60 * 60 * 1000)))
    }
}
).sort({ "date": -1 })