How can I create indexes for different combinations of fields in Firestore?

Question

Suppose I have a users collection that I want to filter in a page of mine. The fields to be filtered on are name, age, location.

For this reason, I create a composite index (name, age, location). The issue is that I want to have the opportunity to filter by any combination of the 3 - name and age, name and location, age and location. When I try to do this, I am prompted to create another composite index for the used combination of fields.

My question is - does that mean that I have to add indexes for all possible composite combinations? If yes, how can I make this happen, if I want to potentially filter by 10 fields, and not only 3? Do I have to create indexes for all combinations myself?

Answer 1

If you are using multiple equality (==) clauses for queries, then you can take advantage of index merging. Cloud Firestore can re-use existing indexes. In your case you have 3 columns name, age, and location and you want to order by hearts, then create three indexes like this:

Collection   Fields indexed
users        ↑ name,      ↑ hearts
users        ↑ age,       ↑ hearts
users        ↑ location,  ↑ hearts

Now you can create different queries with combination of name, age and location using multiple equality (==) clauses.

You can refer to the Firestore documentation about index merging here