startAt second argument has no effect

[esprehn]

[REQUIRED] Describe your environment

• Operating System version: OS X 10.12.6
• Firebase SDK version: Firebase admin 4.1.4
• Firebase Product: database

[REQUIRED] Describe the problem

Using startAt with a query appears to have no effect.

Relevant Code:

  const a: any = await ref.orderByChild('timestamp').startAt(1).limitToFirst(3).once('value');
  const keysA: string[] = [];
  a.forEach((s: any) => { keysA.push(s.key!); return false; });
  console.log(keysA);

  const b: any = await ref.orderByChild('timestamp').startAt(1, keysA[keysA.length - 1]).limitToFirst(3).once('value');
  const keysB: string[] = [];
  b.forEach((s: any) => { keysB.push(s.key!); return false; });
  console.log(keysB);
  console.log(keysA.join() === keysB.join());

[ '-Kstq4UIQPsLL-8EpKTS',
  '-Kstv8g-In43jQOrCpNU',
  '-Kstve77XYA9VlORXm3F' ]
[ '-Kstq4UIQPsLL-8EpKTS',
  '-Kstv8g-In43jQOrCpNU',
  '-Kstve77XYA9VlORXm3F' ]
true

No matter what I pass as the second argument to startAt it doesn't seem to change the values returned.

[esprehn]

I tried firebase-admin 5.4.3 and I see the same thing.

[puf]

When you pass two arguments to startAt, Firebase first filters by the first argument. Then it uses the second argument to find the unique key within the results.

  const a: any = await ref.orderByChild('timestamp').startAt(1).limitToFirst(3).once('value');
  const keysA: string[] = [];
  var lastTimestamp;
  a.forEach((s: any) => { keysA.push(s.key!); lastTimestamp = s.val().timestamp; });
  console.log(keysA);

  const b: any = await ref.orderByChild('timestamp').startAt(lastTimestamp, keysA[keysA.length - 1]).limitToFirst(3).once('value');
  const keysB: string[] = [];
  b.forEach((s: any) => { keysB.push(s.key!); return false; });
  console.log(keysB);
  console.log(keysA.join() === keysB.join());

Also see:

• Firebase orderByChild with startAt()'s second argument w/ pagination not ordering
• Firebase Query order by and start at name
• Pagination using startAt() when ordering by child