dynamial query in firebase firestore in flutter

I am trying to dynamical query in firestore for <= and >= operator.
that is mean I wanna add each key and value dynamical to the query
but I getting an error that it will not work on firebase.

> All where filters with an inequality (<, <=, >, or >=) must be on the same field. But you have inequality filters on 'FieldPath([price])' and 'FieldPath([meter])'.
'package:cloud_firestore/src/query.dart':
Failed assertion: line 780 pos 13: 'hasInequality == field'

My code:

class HomePage extends StatefulWidget {

  @override
  _HomePageState createState() => _HomePageState();
}

class _HomePageState extends State<HomePage> {
  late Query _query;
  final Map<String, dynamic> _filters = {
    'price': 500,
    'meter': 120,
  };
@override
  void initState() {
    super.initState();
    _query = FirebaseFirestore.instance.collection('items');
    for (var key in _filters.keys) {
      if (_filters[key] != null) {
        _query = _query.where(key, isGreaterThanOrEqualTo: _filters[key]);
      }
    }
  }
@override
  Widget build(BuildContext context) {
    return Scaffold(
      appBar: AppBar(
        title: const Text('My App'),
      ),
      body: StreamBuilder<QuerySnapshot>(
        stream: _query.snapshots(),
        builder: (BuildContext context, AsyncSnapshot<QuerySnapshot> snapshot) {
          if (!snapshot.hasData) {
            return const CircularProgressIndicator();
          }
          List<DocumentSnapshot> documents = snapshot.data!.docs;
          return ListView.builder(
            itemCount: documents.length,
            itemBuilder: (BuildContext context, int index) {
              DocumentSnapshot document = documents[index];
              return ListTile(
                title: Text('${document['price']}'),
                subtitle: Text(
                    '${document['meter']} m² / ${document['landMeter']} m²'),
              );
            },
          );
        },
      ),
    );
  }
}

is there any way to work around this limitation?
or dynamic querying?

If you check the Firestore documentation on query limitations it says:

> In a compound query, range (<, <=, >, >=) and not equals (!=, not-in) comparisons must all filter on the same field.

Your code is adding isGreaterThanOrEqualTo (>=) conditions on both price and meter fields, which does not meet this limit.

The problem is not so much that you're building your query dynamically, but that you're trying to add isGreaterThanOrEqualTo conditions on multiple fields, which Firestore doesn't support.

One options is to perform only one condition on the database, and do further filtering in your application code.

Another workaround is (as usual when dealing with NoSQL databases) to add additional data to allow the use-case, although I'm not sure if it applies here.

The closest I can think of, you could add a single field with both of the values:

price_meter: "500_120"

You could then do a notEqual query on this composite value, but it won't be easy to implement a double >= this way, so client-side filtering might be your only option for that.