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

issue に示されている admin.database.Database.ref のクエリチェーンから始め、特に orderByKey()、limitToFirst()、startAfter() を確認します。提供されているページネーションループを使って、SDK 11.11.0 と 11.4.1 の違いを再現します。十分な数のキーが残っている場合に、lastDocument.key の後の 100 件を要求するクエリが 100 件を返し、リグレッションに対するカバレッジがあることを完了条件とします。

[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;
  }