FireStore：如何在强制执行唯一字段值的同时插入带有自动id的文档？

Question

const query = firestore.collection(`/fruits`).where("name", "==", "banana").limit(1);

await firestore.runTransaction(async transaction => {
    const querySnapshot = await transaction.get(query);
    if (querySnapshot.length == 0) {
        const newRef = firestore.collection(`/fruits`).doc();
        await transaction.create(newRef, { name: "banana" });
    }
});

const hash = computeHash("banana");
const uniqueIndexRef = firestore.doc(`/fruitsNameUniqueIndex/${hash}`);

try {
    await firestore.runTransaction(async transaction => {
        transaction.create(uniqueIndexRef, {});

        const newRef = firestore.collection(`/fruits`).doc();
        transaction.create(newRef, { name: "banana" });
    });
} catch (error) {
    console.log("fruit not inserted", error.message);
}

Answer 1

newRef保证不会被使用吗？

它实际上保证是唯一的。两个随机生成的文档ID的可能性非常小。

另见：

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