我想在Firestore文档中存储一个有序的图像路径列表。使用包含位置的元数据和链接到文档的标签将图像上载到存储器。预期的图像量是已知的。几乎同时完成图像的上传。
对,我知道,我是通过将图像路径列表存储为数组来实现的。简而言之:上传图像,使用事务读取文档,更改阵列并再次保存。事务永远不会失败,但有时一个数组项在上传另一个图像后再次消失。
我的两个问题是:数组是NoSql数据库中针对此问题的最佳结构吗?尽管交易,为什么数组项目会消失?
export const addImageToTag = functions.storage.object().onFinalize(async (object) => {
try {
const tag = object.metadata.Tag;
const position = object.metadata.Position;
const tagRef = db.collection(COLLECTION_TAGS).doc(tag)
const tagSnapshot = await db.runTransaction(t => t.get(tagRef));
const images = tagSnapshot.data().images;
images[position] = object.name;
let uploadCount = 0;
for (let i = 0; i < tagSnapshot.data().imageCount; i++) {
if (images[i].length > 0) {
uploadCount++;
} else {
break;
}
}
let state;
if (tagSnapshot.data().imageCount === uploadCount) {
state = STATE_ACTIVE;
} else {
state = STATE_UPLOADING;
}
await tagSnapshot.ref.update({
images: images,
state: state
});
console.log('Image ', position, ' of tag ', tag, 'added')
} catch (error) {
console.error('Call failed: ', error)
}
});
第二个问题得到了回答,实际上将代码放在事务块中就可以了。我读过使用tagSnapshot.ref
引用标签文件就足够了,这是错误的。
export const addImageToTag = functions.storage.object().onFinalize(async (object) => {
try {
const tag = object.metadata.Tag;
const position = object.metadata.Position;
const tagRef = db.collection(COLLECTION_TAGS).doc(tag)
await db.runTransaction(async transaction => {
const tagSnapshot = await transaction.get(tagRef)
const images = tagSnapshot.data().images;
images[position] = object.name;
let uploadCount = 0;
for (let i = 0; i < tagSnapshot.data().imageCount; i++) {
if (images[i].length > 0) {
uploadCount++;
} else {
break;
}
}
let state;
if (tagSnapshot.data().imageCount === uploadCount) {
state = STATE_ACTIVE;
} else {
state = STATE_UPLOADING;
}
transaction.update(tagRef, {
images: images,
state: state
});
if (state === STATE_ACTIVE) {
console.log('All images of tag ', tag, ' were succesfully added')
}
});
} catch (error) {
console.error('Call failed: ', error)
}
});