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Firebase query orderByKey().limitToFirst(n).startAfter() returns n-1 items iso n

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#2,350 4 comments 1 reaction 0 assignees View on GitHub

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
38/100
Issue type
Bug
Clarity
Mostly clear
Activity status
Stale
Tech stack
firebase, node.js, typescript
Domain
databases

Research direction

Start with the admin.database.Database.ref query chain shown in the issue, especially orderByKey(), limitToFirst(), and startAfter(). Reproduce the difference between SDK 11.11.0 and 11.4.1 using the provided pagination loop. Done means a query requesting 100 items after lastDocument.key returns 100 when enough keys remain, with coverage for the regression.

Written by the indexing model from the issue text.

Description

api: database
[READ] Step 1: Are you in the right place?

yes

[REQUIRED] Step 2: Describe your environment
  • Operating System version: Ubuntu 22.04 lts
  • Firebase SDK version: 11.11.0
  • Firebase Product: realtime database (auth, database, storage, etc)
  • Node.js version: 16.20.2
  • NPM version: 8.19.4
[REQUIRED] Step 3: Describe the problem

Firebase query of type:
admin.database.Database.ref('collection').orderByKey().limitToFirst(100).startAfter(lastKey) only returns 99 items iso 100 even if more keys are in the firebase realtime database.

On version 11.4.1 of firebase-admin this query behaves as expected and 100 items are returned.

Steps to reproduce:

What happened? How can we make the problem occur?
This could be a description, log/console output, etc.

Relevant Code:
let query;
let lastDocument = null;
let lastBatchSize: number = 100;

while (lastBatchSize === 100) {
    query = database.ref('collection').orderByKey()
      .limitToFirst(100);

    if (lastDocument !== null) {
      query = query.startAfter(lastDocument.key);
    }

    const snapshot = await query.get();
    const keys = Object.keys(snapshot.val() || {});
    const docs = keys.map((key) => snapshot.child(key));

    if (docs.length === 0) break;
    console.log("docs length " + docs.length); //prints 99 on 11.11.0, prints 100 on 11.4.1

    if (docs.length) {
      lastDocument = docs[docs.length - 1];
    }
    lastBatchSize = docs.length;
  }
Dominant language
TypeScript
Stars
1.7k
Forks
419
Avg merge
4d 20h
Merged PRs (30d)
16

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