Firestore: No reponse form the getDocs() when used with the query constraints endBefore & limitToLast

[Thanga-Ganapathy]

[REQUIRED] Describe your environment

• Operating System version: Pop!_OS 21.10
• Browser version: Google Chrome Version 100.0.4896.88 (Official Build) (64-bit)
• Firebase SDK version: 9.6.11
• Firebase Product: firestore
• React 18.0.0

[REQUIRED] Describe the problem

There was no response from the getDocs() function when used with query constraints endBefore & limitToLast.

Earlier, this was working on the Beta(9.0.0-beta.8) version of the SDK. After an upgrade to the latest version, it broke.

My main concern is that while awaiting a response from the getDocs function, it does not throw any errors either.

Steps to reproduce:

1. Add some data to a collection.
2. Get the first page using the query with orderBy(name) and limit(5).
3. Get the next page using the query with startAfter(page1 last cursor), orderBy(name) and limit(5).
4. Get the prev page using the query with endBefore(page2 first cursor), orderBy(name) and limitToLast(5).
5. No response or error from the prev page query.

Relevant Code:

async function runTest() {
  const db = getFirestore();
  const ref = collection(db, "items");

  // add test data
  const batch = writeBatch(db);
  [...new Array(10)].forEach((a, i) => {
    batch.set(doc(ref, "Item" + (i + 1)), { name: "Item" + (i + 1) });
  });
  await batch.commit();

  // get first page
  const page1 = await getDocs(query(ref, orderBy("name"), limit(5))).then(
    (snap) => {
      console.log(
        "page 1",
        snap.docs.map((doc) => doc.data().name)
      );
      return snap.docs;
    }
  );

  // get next page
  const page2 = await getDocs(
    query(ref, orderBy("name"), limit(5), startAfter(page1[page1.length - 1]))
  ).then((snap) => {
    console.log(
      "page 2",
      snap.docs.map((doc) => doc.data().name)
    );
    return snap.docs;
  });

  // get prev page
  await getDocs(
    query(ref, orderBy("name"), limitToLast(5), endBefore(page2[0]))
  ).then((snap) => {
    console.log(
      "should be page 1",
      snap.docs.map((doc) => doc.data().name)
    );
    return snap.docs;
  });
}

runTest();

/*
Output: 

page 1 (5) ['Item1', 'Item10', 'Item2', 'Item3', 'Item4']
page 2 (5) ['Item5', 'Item6', 'Item7', 'Item8', 'Item9']
*/

[nwaughachukwuma]

I can confirm that getDocs doesn't resolve with or without query constraints

[wu-hui]

Just want to provide an update: there is another bug reported on endBefore and limitToLast, and it is fixed via: #6168

Although the two reports do not have the same symptom, it is possible that they are from different platforms.

Let's wait to see if the next release did fix the issue. We will look into this again if it does not.

[Thanga-Ganapathy]

@wu-hui Thanks for the fix.

I have tested this in the firebase@canary. It is working fine and seems to be fixed.

One suggestion: in the future, please ensure that it throws some errors when awaiting a response from the async functions if something goes wrong with some kind of timeout or any other solution. Because when the async functions do not respond, the app exhibits undesirable behaviour.

Please close this issue if it can be closed without any further action needed.

Thanks.

[nwaughachukwuma]

I just tested firebase": "9.6.11-canary.dc0e92632" and it doesn't seem resolved yet. In the snippet below, the console statement never gets called.

const activeUsers = await getDocs(query(colRef, where('status', '==', 'active')))
console.log('resolved!')

[wu-hui]

Hi @Thanga-Ganapathy

Thanks for confirming! I do not know why it manifest as a timeout in your environment, maybe something we should look into.

Hi @nwaughachukwuma

Are you reporting a new issue, or you are experiencing the same issue with endBefore and limitToLast?

It seems like you are reporting a new one, from the snippet you pasted. I am going to close this one, and feel free to open a new ticket for your issue.

[nwaughachukwuma]

Hi @wu-hui, I considered the issues to be the same or have the same root cause. My observation is that getDocs never resolves when passed a query constraint - in my case, it doesn't resolve with a simple where constraint

const activeUsers = await getDocs(query(colRef, where('status', '==', 'active')))
console.log('resolved!') // <-- never reached

[nwaughachukwuma]

I can confirm that this now works for me

[mariusschroeter]

Hi @wu-hui, I considered the issues to be the same or have the same root cause. My observation is that getDocs never resolves when passed a query constraint - in my case, it doesn't resolve with a simple where constraint

const activeUsers = await getDocs(query(colRef, where('status', '==', 'active')))
console.log('resolved!') // <-- never reached

For some reason this doesnt get data for me. ^

But this does:
const q = query(colRef, where('status', '==', 'active'))
const activeUsers = await getDocs(q)