Composite index from an array of objects

SQL++
,
1

Hello,
I have a bucket with documents like this:

{
	"fd": [{
			"ac": "AF",
			"d": 30,
			"fn": 1096,
			"ym": 1911
		}, {
			"ac": "AF",
			"d": 9,
			"fn": 1053,
			"ym": 2009
		}, {
			"ac": "BA",
			"d": 29,
			"fn": 1002,
			"ym": 2006
		}, {
			"ac": "QR",
			"d": 6,
			"fn": 1764,
			"ym": 2011
		}
	],
	"ts": 1572258925.187879,
	"yld": [
		"PEKAMS",
		"CDGORY"
	]
}

I am trying to index, as a composite index the following fields: fd.ac, fd.ym, fd.d, i.e. I need to be able to perform query only targeting the first 1 or 2 fields.

I’ve create an index like this:

CREATE INDEX idx1 ON bucket (DISTINCT ARRAY [f.ac, f.ym, f.d] FOR f IN fd END)

But Couchbase is not able to use it as a composite index, only as a “normal” index, e.g. each element in the array pushes only 1 key in the index.

For instance this query will not work:

SELECT RAW meta().id FROM bucket WHERE ANY f IN fd SATISFIES (f.ac == ‘AF’) END

Couchbase will tell me that no index is suitable for this query (even if I explicitly add a USE INDEX).

Only queries like this, specifying all the fields work:

SELECT RAW meta().id FROM bucket WHERE ANY f IN fd SATISFIES [f.ac, f.ym, f.d] == [“AF”, 1911, 30] END

Going through the documentation I’m not able to find a case like that. Is there a way to do this in Couchbase? Currently I’m using version 5.5.

Thanks a lot for your help!