Search in array child firestore - node.js

Question

How can I retrieve all the documents who match a child in a data structure like this:
{
[
id: {
name: "name",
products: {
items: [
productName: "this is the product Name"
]
}
}
]
}
The parameter i try to compare is the one inside products.items[0].productName.
this is how i tried but it does not retrieve anything:
try{
var data = [];
const byName = await dbRef.where('producto.items[0].producto', '==', req.params.nombre).get();
console.log(byName);
if (byName.empty) {
console.log('No matching documents.');
res.send('No matching documents.');
return;
}
byName.forEach(doc => {
console.log(doc.id, '=>', doc.data());
data.push(doc.data());
});
res.send(data);
}catch(err){
res.send(err);
}

Answer 1

If you want to search across all items in the items array for one that matches the value you have, you can use the array-contains operator:
dbRef.where('producto.items', 'array-contains', { producto: req.params.nombre})
But note that this only works if the array only contains the producto field in each item. The reason is that array-contains (and other array-level operators) work on complete items only.
So if the items in producto.items have multiple subfields, and you want to match on one/some of them, you can't use array-contains. In that case, you're options are:
Store the items names in a separate/additional array field product-names and then query on that with array-contains.
Store the array items in a subcollection and query that.
Use a map instead of an array to store these values. This will generate many extra indexes though, which both adds to your storage cost, and may get you to the limit on the number of indexes.