The title might imply this is nonsensical, but I’m trying to limit the amount of data retrieved from Firebase. I have a query structured like this:

for (final Map.Entry<String, String> entry : map.entrySet())
{
    final Query dataQuery = mFirebaseRef.child("someChild").child(entry.getKey());

    dataQuery.addListenerForSingleValueEvent(new ValueEventListener()
    {
        // do something with data
    }
}

Each child returned has a timestamp. Now I want to limit the query further by only returning children in the Map that have timestamp newer than the previous query.

If I form a query such as this:

final Query dataQuery = mFirebaseRef.child("someChild").orderByChild("timestamp").startAt(timeMsec);

Then it works and the query returns all children meeting that criteria.

But I want to first limit only to children in the Map (using .child(entry.getKey()), and then check the timestamp values that meet that criteria. i.e.

for (final Map.Entry<String, String> entry : map.entrySet())
{
    final Query dataQuery = mFirebaseRef.child("someChild").child(entry.getKey()).orderByChild("timestamp").startAt(timeMsec);
   ... 

And this doesn’t work even when children have a timestamp that meet the criteria. Is this a specific limitation that orderByChild doesn’t work when the query returns a single child? A simple check is to use timeMsec = 0 and nothing is returned by the query.