Firestore如何停止交易? [英] Firestore how stop Transaction?
本文介绍了Firestore如何停止交易?的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
在事务中,我只想在不存在数据的情况下写数据
In transaction I only want to write data if data not present
DocumentReference callConnectionRef1 = firestore.collection("connectedCalls").document(callChannelModel.getUid());
firestore.runTransaction(new Transaction.Function < Void > () {
@Override
public Void apply(Transaction transaction) throws FirebaseFirestoreException {
DocumentSnapshot snapshot = transaction.get(callConnectionRef1);
Log.d(TAG, callChannelModel.getUid());
if (!snapshot.exists()) {
//my code
transaction.set(callConnectionRef1, model);
} else {
//do nothing
}
return null;
});
您可以在我的文档参考中看到基于uid,并且在我的日志中我正在打印uid
You can see in my Document reference is uid based and in my log I am printing uid
因此,在不存在uid数据的情况下,我的日志仅打印一次,而我在其他地方调用transaction.set(),它继续显示uid日志,其中已经存在数据,如果不调用transaction.set( )
So where uid's data not exist my Log prints only once and I call transaction.set() elsewhere it keep showing Log of uid where data exists already it looks like my transaction keep running if I don't call transaction.set()
如何阻止它.
推荐答案
文档中提供了一个示例,只是抛出一个异常,它将退出事务并停止执行.
There is an example given in the documentation, just throw an exception and it will exit the transaction and stop executing.
db.runTransaction(new Transaction.Function<Double>() {
@Override
public Double apply(Transaction transaction) throws FirebaseFirestoreException {
DocumentSnapshot snapshot = transaction.get(sfDocRef);
double newPopulation = snapshot.getDouble("population") + 1;
if (newPopulation <= 1000000) {
transaction.update(sfDocRef, "population", newPopulation);
return newPopulation;
} else {
throw new FirebaseFirestoreException("Population too high",
FirebaseFirestoreException.Code.ABORTED);
}
}
}).addOnSuccessListener(new OnSuccessListener<Double>() {
@Override
public void onSuccess(Double result) {
Log.d(TAG, "Transaction success: " + result);
}
})
.addOnFailureListener(new OnFailureListener() {
@Override
public void onFailure(@NonNull Exception e) {
Log.w(TAG, "Transaction failure.", e);
}
});
DocSnippets.java
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