Is it possible to query a Firestore collection to get all documents whose array filed has a specific prefix word?
for example,
User A uid : uid000 region list : [ USA-CA, USA-NY]
User B uid : uid001 region list : [ USA-ALL, EU-FR]
User C uid : uid002 region list : [ASIA-JP, ASIA-CH]
when fetching the user list like above from Firestore and select 'USA-' to filter, I want to get all users whose region list even has an element that starts with 'USA-'
result : userlist : [ User A, User B ]
when fetching the user list like above from Firestore and selecting 'USA-' to filter, I want to get all users whose region list even has an element that starts with 'USA-'
No, you cannot achieve that using an array. However, if you're allowed to change the database structure a little bit, then you can achieve the same result. Since the USA- is the common element of those arrays, then you should consider naming the array like so:
Firestore-root
|
--- users (collection)
|
--- uid000 (document)
| |
| --- USA: ["CA", "NY"]
|
--- uid001 (document)
| |
| --- USA: ["ALL"]
| |
| --- EU: ["FR"]
|
--- uid002 (document)
|
--- ASIA: ["JP", "NY"]
To query the users who have the USA array present in the document, please use the following lines of code:
FirebaseFirestore db = FirebaseFirestore.getInstance();
db.collection("products").whereNotEqualTo("USA", null).get().addOnCompleteListener(new OnCompleteListener<QuerySnapshot>() {
@Override
public void onComplete(@NonNull Task<QuerySnapshot> task) {
if (task.isSuccessful()) {
for (QueryDocumentSnapshot document : task.getResult()) {
Log.d(TAG, document.getId());
}
} else {
Log.d(TAG, "Error getting documents: ", task.getException());
}
}
});
As you can see we query against the USA field for existence. The result in the logcat will be:
uid000
uid001
