Find document with its surroundings in MongoDB - mongodb

Question

I have mongo collection with documents like below:
{
_id: [ObjectId]
writeDate: [DateTime]
publishDate: [DateTime]
...
}
I usually display list of such documents sorting by publishDate first and then on writeDate.
Now when I get given document _id I need to fetch list containing: 2 previous documents, this document and 2 next documents. So it should look like as follows:
[1,2,4,3,6,7,8,5,9,0]
if given id is 6 I should get
[4,3,6,7,8]
and if id is 4 I should get
[1,2,4,3,6]
The thing is that publish dates may be the same (then I additionally sort by writeDate), so I suppose I can't just order using $gte and $lte with given document's date. Also _id are not guaranteed to be in order.
Do you have any clues on how to do this?

Answer 1

You can not do this in one query, but you will have to use three instead:
// current
r = db.so.findOne( { _id: 6 } );
// previous 2
db.so
.find( { publishDate: { $lte: r.publishDate }, _id: { $ne: 6 } )
.sort( { publishDate: -1 } )
.limit( 2 );
// next 2
db.so
.find( { publishDate: { $gte: r.publishDate }, _id: { $ne: 6 } )
.sort( { publishDate: 1 } )
.limit( 2 );