How to find a document with an element's value greater than size of array?

Question

I want to find a document with x larger than the size of the array y. I'm doing this:

db.find(x: { $gt: { $size: "$y" } })

Doesn't find anything. What is wrong?

The last document should be returned:

{x: 0, y: [0, 1]}
{x: 1, y: [0, 1]}
{x: 2, y: [0, 1]}
{x: 3, y: [0, 1]} # 3 is larger than 2

mickl · Accepted Answer · 2019-07-21 20:05:28Z

1

You need $expr to compare two fields from the same document in your query:

db.col.find({ $expr: { $gt: [ "$x", { $size: "$y" } ] } })

answered Jul 21, 2019 at 20:05

mickl

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