Firestore to query by an array's field value

As Frank has explained in his answer it is not possible, with array-contains, to query for a specific property of an object stored in an array.

However, there is a possible workaround: it is actually possible to query for the entire object, as follows, in your case:

db.collection('identites').where("partyMembers", "array-contains", {id: "7LNK....", name: "John Travolta"})

Maybe this approach will suit your needs (or maybe not....).

The array-contains operations checks if an array, contains a specific (complete) value. It can't check if an array of objects, contains an item with a specific value for a property.

The only way to do your query, is to add an additional field to your document with just the value you want to query existence on. So for example: partyMemberNames: ["John Travolta", "Olivia Newton"].