Limiting Firebase queries with startAt and endAt

Question

Limiting Firebase queries with startAt and endAt

I need to retrieve the first 100 results from my Firebase data, followed by the next 100, and so on. Despite trying multiple methods, I have not been successful.

Method 1

ref.child('products').orderByChild('domain').startAt(0).endAt(100).once('value').then(function(snapshot) {});

Method 2

ref.child('products').orderByChild('domain').startAt(0).limitToFirst(100).once('value').then(function(snapshot) {});

Method 3

ref.child('products').startAt(0).endAt(100).once('value').then(function(snapshot) {});

Each time the snapshot returned is null. Is there a way in Firebase to achieve the desired range of data?

javascript firebase firebase-realtime-database

Answer 1

Answer №1

Utilizing the orderByChild() method requires subsequent calls to startAt(), endAt(), or equalTo() with a child value, not an index. Unless the value of domain is a sequential index (which is highly unlikely), this approach will not yield the desired results.

A more effective strategy involves storing the domain value of the last child retrieved and passing it into startAt() for the next set of data:

var productsRef = ref.child('products');
var lastKnownDomainValue = null;
var pageQuery = productsRef.orderByChild('domain').limitToFirst(100);
pageQuery.once('value', function(snapshot) {
  snapshot.forEach(function(childSnapshot) {
    lastKnownDomainValue = childSnapshot.child('domain').val();
  });
});

By maintaining the variable lastKnownDomainValue, you can easily fetch the next batch of children by passing this value into startAt():

var nextQuery = productsRef.orderByChild('domain').startAt(lastKnownDomainValue).limitToFirst(100);

Remember to update the lastKnownDomainValue as you iterate over the children once again.

Answer 2

Utilizing the orderByChild() method requires subsequent calls to startAt(), endAt(), or equalTo() with a child value, not an index. Unless the value of domain is a sequential index (which is highly unlikely), this approach will not yield the desired results.

A more effective strategy involves storing the domain value of the last child retrieved and passing it into startAt() for the next set of data:

var productsRef = ref.child('products');
var lastKnownDomainValue = null;
var pageQuery = productsRef.orderByChild('domain').limitToFirst(100);
pageQuery.once('value', function(snapshot) {
  snapshot.forEach(function(childSnapshot) {
    lastKnownDomainValue = childSnapshot.child('domain').val();
  });
});

By maintaining the variable lastKnownDomainValue, you can easily fetch the next batch of children by passing this value into startAt():

var nextQuery = productsRef.orderByChild('domain').startAt(lastKnownDomainValue).limitToFirst(100);

Remember to update the lastKnownDomainValue as you iterate over the children once again.

Limiting Firebase queries with startAt and endAt

Answer №1

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