Query not picking the correct index

SQL++
, ,
1

I am having trouble getting my query to use the right index and I am wondering what I am doing something wrong with either my query or my index.

Here is the query I am running:

SELECT RAW cd.chargeCategoryIds
    FROM app cd
    WHERE cd.type = "chargeDscrp"
    AND cd.chargeCategoryIds IS VALUED AND cd.chargeCategoryIds != []
    GROUP BY chargeCategoryIds
    ORDER BY chargeCategoryIds

This is the shape of the documents I am querying: 

{
  "chargeCategoryIds": [
    "chargeCat-1",
    "chargeCat-2",
    "chargeCat-3"
  ],
  "createdDate": "2021-01-06T06:36:21.6380541+00:00",
  "description": null,
  "docId": "chargeDscrp-1234",
  "lastModified": "2021-04-07T06:13:39.1283129+00:00",
  "schemaVer": "2021.4.5.1",
  "tenantName": "MyTenant",
  "tokens": [],
  "type": "chargeDscrp"
}

This is the index I want it to use:

CREATE INDEX app_idx_chargeDscrp_chargeCategoryIds_distinct ON app((distinct (array t for t in chargeCategoryIds end))) WHERE (type = “chargeDscrp”)

This is the index it ends up using which is very slow:

CREATE INDEX app_part_idx_doc_type_tenant ON app(type,tenantName)

2 
CREATE INDEX ix1 ON `app` (ALL chargeCategoryIds) WHERE ( `type` = "chargeDscrp");

SELECT DISTINCT RAW cId
FROM app AS cd
UNNEST cd.chargeCategoryIds AS cId
WHERE cd.type = "chargeDscrp" AND cId IS NOT NULL
ORDER BY cId;
3

Thanks this works great.