Firestore查询游标始终返回相同的数据

Question

我正在处理一个虚拟表，该表懒洋洋地订阅firestore中的一批新项目。问题是，无论startAt索引不同，查询游标都会返回同一批数据。

const subscribeForItems = (
startIndex: number,
handleItems: (items: FirestoreItem[]) => void,
): (() => void) => {
const firestoreQuery = query(
collection(firestore, RootCollections.Items),
orderBy('price'),
startAt(startIndex),
limit(LIMIT),
);
return onSnapshot(firestoreQuery, (querySnapshot) => {
const items: FirestoreItem[] = [];
querySnapshot.forEach((doc) => {
items.unshift(
FirestoreUtils.extractDocumentData<FirestoreItem>(doc),
);
});
console.log(startIndex)// START INDEX IS DIFFERENT HERE EACH INVOCATION
console.log(items)// ITEMS ARE SAME HERE EACH INVOCATION (AS IF I'M ALWAYS PASSING THE SAME START INDEX)
handleItems(items);
});
};

Answer 1

所以问题是设置限制。代替

const firestoreQuery = query(
collection(firestore, RootCollections.Items),
orderBy('price'),
startAt(startIndex),
limit(LIMIT),
);

应该是

const firestoreQuery = query(
collection(firestore, RootCollections.Items),
orderBy('price'),
startAt(startIndex),
limit(LIMIT + startIndex),
);

我发现limit((方法的命名违反直觉，如果我需要自己添加，也许endAt((会是一个更好的名称