elasticsearch filtering by the size of a field that is an array

Question

How can I filter documents that have a field which is an array and has more than N elements?

How can I filter documents that have a field which is an empty array?

Answer 1

If you have an array of objects that aren't mapped as nested, keep in mind that Elastic will flatten them into:

attachments: [{size: 123}, {size: 456}] --> attachments.size: [123, 456]

So you want to reference your field as doc['attachments.size'].length, not doc['attachments'].length, which is very counter-intuitive.

Same for doc.containsKey(attachments.size).

The .values part is deprecated and no longer needed.