CODEWITHSUNDEEP
firebasegoogle-cloud-firestore
user93796
user93796

Reputation: 18399

Optimizing the number of reads from firestore server using caching or snapshot listener

I am rendering the following view using Firebase. So basically the search is powered by a Firebase query.

enter image description here

I am using the following code:

Query query = FirebaseUtils.buildQuery(
        fireStore, 'customers', filters, lastDocument, documentLimit);
    print("query =" + query.toString());
    QuerySnapshot querySnapshot = await query.getDocuments();
    print("Got reply from firestore. No of items =" +  querySnapshot.documents.length.toString());

Questions:

  1. If the user hits the same query, again and again, it still hits the server. I checked this by using doc.metadata.isFromCache and it always returns false.

  2. Will using query snapshots help in reduce no of reads for this search query? I guess no. As the user is changing the query again and again.

  3. Any other way to limit the number of reads?

Upvotes: 0

Views: 121

Answers (1)

Alex Mamo
Alex Mamo

Reputation: 1

  1. If the user hits the same query, again and again, it still hits the server. I checked this by using doc.metadata.isFromCache and it always returns false.

If you are online, it will always return false and that's the expected behavior since the listener is always looking for changes on the server. If you want to force the retrieval of the data from the cache while you are online, then you should explicitly specify this to Firestore by adding Source.CACHE to your get() call. If you're offline, it will always return true.

  1. Will using query snapshots help in reduce no of reads for this search query? I guess no. As the user is changing the query again and again.

No, it won't. What does a query snapshot represent? It's basically an object that contains the results of your query. However, if you perform a query, "again and again", as long as it's the same query and nothing has changed on the server, then you will not be charged with any read operations. This is happening because the second time you perform the query, the results are coming from the cache. If you perform each time a new search, you'll always be billed with a number of read operations that are equal with the number of elements that are returned by your query. Furthermore, if you create new searches and the elements that are returned are already in your cache, then you'll be billed with a read operation only for the new ones.

  1. Any other way to limit the number of reads?

The simplest method to limit the results of a query is to use a limit() call and pass as an argument the number of elements you want your query to return:

limit(10)

Upvotes: 1

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