Select documents where doc.arr[i]>n

Question

I have a collection with elements like this:

{
name: "Smith",
fields: [10, 20, 30]
}

Is there a way to select documents where second value of fields array ( fields[1]) > 15 ?

Minh Tuan Nguyen · Accepted Answer · 2017-08-18T10:10:58.260

2

One solution is:

 //create multikey index on field
db.test.createIndex({"fields.1" : 1})

db.test.find({"fields.1" : {$gt : 15}})

edited Aug 18 '17 at 10:10

answered Aug 18 '17 at 05:56

Minh Tuan Nguyen

This can be a solution if you also include the Index on "fields.1". Can You take a look on "https://docs.mongodb.com/manual/core/index-multikey/" and maybe update your answer? – Daniele Tassone Aug 18 '17 at 08:35
Thank you for your comment! – Minh Tuan Nguyen Aug 18 '17 at 09:23
Just to say, is more optimized "fields.1" instead of "fields" index. Besides this, i will upvote your reply. – Daniele Tassone Aug 18 '17 at 09:48
yes you are right! it must be {"fields.1" : 1}. Otherwise mongo will perform the full coll scan. – Minh Tuan Nguyen Aug 18 '17 at 10:10

1 Answers1