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[英]Android Studio - How do I get documents from a sub-collection in Firestore?
[英]How do you iterate through documents in a sub-collection within a transaction for firestore android?
我希望能夠刪除子集合中的所有文檔,這是android中交易的一部分。 我發現以下代碼,但這是針對Node.js的
// First perform the query
db.collection('job_skills').where('job_id','==',post.job_id).get()
.then(function(querySnapshot) {
// Once we get the results, begin a batch
var batch = db.batch();
querySnapshot.forEach(function(doc) {
// For each doc, add a delete operation to the batch
batch.delete(doc.ref);
});
// Commit the batch
return.batch.commit();
}).then(function() {
// Delete completed!
// ...
});
任何幫助將不勝感激!
謝謝!
我在您的代碼中看到的不是交易,而是批處理。 因此,如果您想使用Android SDK刪除集合中的所有文檔,建議您使用以下方法:
private void deleteCollection(final CollectionReference collection, Executor executor) {
Tasks.call(executor, new Callable<Object>() {
@Override
public Object call() throws Exception {
int batchSize = 10;
Query query = db.collection("job_skills").whereEqualTo("job_id", job_id);
List<DocumentSnapshot> deleted = deleteQueryBatch(query);
while (deleted.size() >= batchSize) {
DocumentSnapshot last = deleted.get(deleted.size() - 1);
query = collection.orderBy(FieldPath.documentId()).startAfter(last.getId()).limit(batchSize);
deleted = deleteQueryBatch(query);
}
return null;
}
});
}
這是deleteQueryBatch()
方法:
@WorkerThread
private List<DocumentSnapshot> deleteQueryBatch(final Query query) throws Exception {
QuerySnapshot querySnapshot = Tasks.await(query.get());
WriteBatch batch = query.getFirestore().batch();
for (DocumentSnapshot snapshot : querySnapshot) {
batch.delete(snapshot.getReference());
}
Tasks.await(batch.commit());
return querySnapshot.getDocuments();
}
即使Firebase團隊不建議刪除操作,因為它具有負面的安全性和性能影響,您仍然可以將其用於小型數據集。
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