firestore query a value under a subfield under field asterisk star

I have this data: { root: { _rEG: { fen: 'value' }, _AS: { fen: 'value' }, _BSSA: { fen: 'value' } } } I want to query like where('root.*.fen', '==', 'value'). How can I do this. I thought about putting all fen values as keys and value to this * path and index like that, is there a better way?

There is no way to use a wildcard in the field name in a query. To implement this use-case, you can: Either create a top-level field with all fen values (using an array-union), and query with array-contains against that field. Or put the _rEG, _AS and _BSSA in documents in a dedicated subcollection, and query against that with a collection group query.