blocks|key|4343485|text|他们刚刚宣布了这项功能，https://firebase.googleblog.com/2019/11/cloud-firestore-now-supports-in-queries.html。|type|unstyled|depth|inlineStyleRanges|entityRanges|offset|length|data|4343486|现在您可以使用这样的查询，但要记住输入大小不能大于10。|4343487|userCollection.where('uid',+'in',+["1231","222","2131"])|style|CODE|4343488|entityMap|0|LINK|mutability|MUTABLE|url|https://firebase.googleblog.com/2019/11/cloud-firestore-now-supports-in-queries.html^0|C|2C|0|0|0|0|1K|0^^$0|@$1|2|3|4|5|6|7|R|8|@]|9|@$A|S|B|T|1|U]]|C|$]]|$1|D|3|E|5|6|7|V|8|@]|9|@]|C|$]]|$1|F|3|G|5|6|7|W|8|@$A|X|B|Y|H|I]]|9|@]|C|$]]|$1|J|3|-4|5|6|7|Z|8|@]|9|@]|C|$]]]|K|$L|$5|M|N|O|C|$P|Q]]]]

They have just announced this functionality, <a href="https://firebase.googleblog.com/2019/11/cloud-firestore-now-supports-in-queries.html" rel="noreferrer">https://firebase.googleblog.com/2019/11/cloud-firestore-now-supports-in-queries.html</a> . 

Now you can use queries like, but mind that the input size can't be greater than 10.

<code>userCollection.where('uid', 'in', ["1231","222","2131"])</code>

blocks|key|4343389|text|在实践中，您可以像这样使用firestore.getAll|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4343390|async+getUsers({userIds})+{
++++const+refs+=+userIds.map(id+=>+this.firestore.doc(`users/${id}`))
++++const+users+=+await+this.firestore.getAll(...refs)
++++console.log(users.map(doc+=>+doc.data()))
}|code-block|syntax|javascript|4343391|或者使用promise语法|4343392|getUsers({userIds})+{
++++const+refs+=+userIds.map(id+=>+this.firestore.doc(`users/${id}`))
++++this.firestore.getAll(...refs).then(users+=>+console.log(users.map(doc+=>+doc.data())))
}|4343393|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|N|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|O|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

In practise you would use firestore.getAll like this
<pre class="lang-js prettyprint-override"><code>async getUsers({userIds}) {
 const refs = userIds.map(id =&gt; this.firestore.doc(`users/${id}`))
 const users = await this.firestore.getAll(...refs)
 console.log(users.map(doc =&gt; doc.data()))
}
</code></pre>
or with promise syntax
<pre class="lang-js prettyprint-override"><code>getUsers({userIds}) {
 const refs = userIds.map(id =&gt; this.firestore.doc(`users/${id}`))
 this.firestore.getAll(...refs).then(users =&gt; console.log(users.map(doc =&gt; doc.data())))
}
</code></pre>

blocks|key|4343353|text|您可以使用如下函数：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4343354|function+getById+(path,+ids)+{
++return+firestore.getAll(
++++[].concat(ids).map(id+=>+firestore.doc(`${path}/${id}`))
++)
}|code-block|syntax|javascript|4343355|可以使用单个ID进行调用：|4343356|getById('collection',+'some_id')|4343357|或ID数组：|4343358|getById('collection',+['some_id',+'some_other_id'])|4343359|entityMap^0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|Q|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|R|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|S|8|@]|9|@]|A|$]]|$1|I|3|J|5|D|7|T|8|@]|9|@]|A|$E|F]]|$1|K|3|L|5|6|7|U|8|@]|9|@]|A|$]]|$1|M|3|N|5|D|7|V|8|@]|9|@]|A|$E|F]]|$1|O|3|-4|5|6|7|W|8|@]|9|@]|A|$]]]|P|$]]

You could use a function like this:

<pre><code>function getById (path, ids) {
 return firestore.getAll(
 [].concat(ids).map(id =&gt; firestore.doc(`${path}/${id}`))
 )
}
</code></pre>

It can be called with a single ID:

<pre><code>getById('collection', 'some_id')
</code></pre>

or an array of IDs:

<pre><code>getById('collection', ['some_id', 'some_other_id'])
</code></pre>

blocks|key|4342882|text|不能，目前还没有办法使用Cloud+Firestore+SDK批量处理多个读请求，因此也没有办法保证您可以一次读取所有数据。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4342883|然而，正如Frank+van+Puffelen在上面的评论中所说的，这并不意味着获取3个文档的速度将是获取1个文档的速度的3倍。在这里得出结论之前，最好先进行自己的测量。|4342884|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

No, right now there is no way to batch multiple read requests using the Cloud Firestore SDK and therefore no way to guarantee that you can read all of the data at once.

However as Frank van Puffelen has said in the comments above this does not mean that fetching 3 documents will be 3x as slow as fetching one document. It is best to perform your own measurements before reaching a conclusion here.

blocks|key|4343242|text|如果使用的是flutter，则可以执行以下操作：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4343243|Firestore.instance.collection('your+collection+name').where(FieldPath.documentId,+whereIn:[list+containing+multiple+document+IDs]).getDocuments();|code-block|syntax|javascript|4343244|这将返回一个包含List<DocumentSnapshot>的Future，您可以根据需要进行迭代。|offset|length|style|CODE|4343245|entityMap^0|0|0|8|M|0^^$0|@$1|2|3|4|5|6|7|O|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|P|8|@]|9|@]|A|$E|F]]|$1|G|3|H|5|6|7|Q|8|@$I|R|J|S|K|L]]|9|@]|A|$]]|$1|M|3|-4|5|6|7|T|8|@]|9|@]|A|$]]]|N|$]]

If you are using flutter, you can do the following:

<pre><code>Firestore.instance.collection('your collection name').where(FieldPath.documentId, whereIn:[list containing multiple document IDs]).getDocuments();
</code></pre>

This will return a Future containing <code>List&lt;DocumentSnapshot&gt;</code> which you can iterate as you feel fit.

blocks|key|4343319|text|当然，最好的方法是通过在云函数中实现Firestore的实际查询？然后，只有一个从客户端到Firebase的往返调用，这似乎就是您所要求的。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4343320|无论如何，您确实希望保留所有的数据访问逻辑，就像这个服务器端一样。|4343321|在内部，可能会有相同数量的对Firebase本身的调用，但它们都会通过Google的超高速互连，而不是外部网络，并结合Frank+van+Puffelen解释的流水线，您应该会从这种方法中获得出色的性能。|4343322|entityMap^0|0|0|0^^$0|@$1|2|3|4|5|6|7|H|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|I|8|@]|9|@]|A|$]]|$1|D|3|E|5|6|7|J|8|@]|9|@]|A|$]]|$1|F|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|G|$]]

Surely the best way to do this is by implementing the actual query of Firestore in a Cloud Function? There would then only be a single round trip call from the client to Firebase, which seems to be what you're asking for.

You really want to be keeping all of your data access logic like this server side anyway.

Internally there will likely be the same number of calls to Firebase itself, but they would all be across Google's super-fast interconnects, rather than the external network, and combined with the pipelining which Frank van Puffelen has explained, you should get excellent performance from this approach.

blocks|key|4343363|text|您可以使用文档IN+(最多10个)执行IN查询：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4343364|import+{
++++query,
++++collection,
++++where,
++++getDocs,
++++documentId,
}+from+'firebase/firestore';

export+async+function+fetchAccounts(
++++ids:+string[]
)+{
++++//+use+lodash+_.chunk,+for+example
++++const+result+=+await+Promise.all(
++++++++chunk(ids,+10).map(async+(chunkIds)+=>+{
++++++++++++const+accounts+=+await+getDocs(
++++++++++++++++query(
++++++++++++++++++++collection(firestore,+'accounts'),
++++++++++++++++++++where(documentId(),+'in',+chunkIds)
++++++++++++++++));
++++++++++++return+accounts.docs.filter(doc+=>+doc.exists()).map(doc+=>+doc.data());
++++++++})
++++);
++++return+result.flat(1);
}|code-block|syntax|javascript|4343365|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

You can perform an IN query with the document IDs (up to ten):
<pre class="lang-js prettyprint-override"><code>import {
 query,
 collection,
 where,
 getDocs,
 documentId,
} from 'firebase/firestore';

export async function fetchAccounts(
 ids: string[]
) {
 // use lodash _.chunk, for example
 const result = await Promise.all(
 chunk(ids, 10).map(async (chunkIds) =&gt; {
 const accounts = await getDocs(
 query(
 collection(firestore, 'accounts'),
 where(documentId(), 'in', chunkIds)
 ));
 return accounts.docs.filter(doc =&gt; doc.exists()).map(doc =&gt; doc.data());
 })
 );
 return result.flat(1);
}
</code></pre>

blocks|key|4343402|text|对于那些遇到同样问题的人，这里有一个示例代码：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4343403|List<String>+documentsIds+=+{your+document+ids};

FirebaseFirestore.getInstance().collection("collection_name")
.whereIn(FieldPath.documentId(),+documentsIds).get().addOnCompleteListener(new+OnCompleteListener<QuerySnapshot>()+{
++++++++++++@Override
++++++++++++public+void+onComplete(@NonNull+Task<QuerySnapshot>+task)+{
++++++++++++++++if+(task.isSuccessful())+{
+++++++++++++++++++++for+(DocumentSnapshot+document+:+Objects.requireNonNull(task.getResult()))+{
++++++++++++++++++++++++YourClass+object+=+document.toObject(YourClass.class);
++++++++++++++++++++++++//+add+to+your+custom+list
++++++++++++++++++++}+++
++++++++++++++++}
++++++++++++++++
++++++++++++}
++++++++}).addOnFailureListener(new+OnFailureListener()+{
++++++++++++@Override
++++++++++++public+void+onFailure(@NonNull+Exception+e)+{
++++++++++++++++e.printStackTrace();
++++++++++++}
++++++++});|code-block|syntax|javascript|4343404|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|I|8|@]|9|@]|A|$]]|$1|B|3|C|5|D|7|J|8|@]|9|@]|A|$E|F]]|$1|G|3|-4|5|6|7|K|8|@]|9|@]|A|$]]]|H|$]]

For some who are stucked in same problem
here is a sample code:
<pre><code>List&lt;String&gt; documentsIds = {your document ids};

FirebaseFirestore.getInstance().collection(&quot;collection_name&quot;)
.whereIn(FieldPath.documentId(), documentsIds).get().addOnCompleteListener(new OnCompleteListener&lt;QuerySnapshot&gt;() {
 @Override
 public void onComplete(@NonNull Task&lt;QuerySnapshot&gt; task) {
 if (task.isSuccessful()) {
 for (DocumentSnapshot document : Objects.requireNonNull(task.getResult())) {
 YourClass object = document.toObject(YourClass.class);
 // add to your custom list
 } 
 }
 
 }
 }).addOnFailureListener(new OnFailureListener() {
 @Override
 public void onFailure(@NonNull Exception e) {
 e.printStackTrace();
 }
 });
</code></pre>

blocks|key|4343110|text|下面是如何在Kotlin中使用Android+SDK来做类似的事情。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4343111|可能不一定在一个往返过程中，但它确实有效地对结果进行了分组，并避免了许多嵌套回调。|4343112|val+userIds+=+listOf("123",+"456")
val+userTasks+=+userIds.map+{+firestore.document("users/${it!!}").get()+}

Tasks.whenAllSuccess<DocumentSnapshot>(userTasks).addOnSuccessListener+{+documentList+->
++++//Do+what+you+need+to+with+the+document+list
}|code-block|syntax|javascript|4343113|请注意，获取特定文档比获取所有文档并过滤结果要好得多。这是因为Firestore为查询结果集向您收费。|4343114|entityMap^0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|M|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|N|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|O|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|P|8|@]|9|@]|A|$]]|$1|K|3|-4|5|6|7|Q|8|@]|9|@]|A|$]]]|L|$]]

Here's how you would do something like this in Kotlin with the Android SDK.
 May not necessarily be in one round trip, but it does effectively group the result and avoid many nested callbacks.

<pre><code>val userIds = listOf("123", "456")
val userTasks = userIds.map { firestore.document("users/${it!!}").get() }

Tasks.whenAllSuccess&lt;DocumentSnapshot&gt;(userTasks).addOnSuccessListener { documentList -&gt;
 //Do what you need to with the document list
}
</code></pre>

Note that fetching specific documents is much better than fetching all documents and filtering the result. This is because Firestore charges you for the query result set.

blocks|key|4343315|text|对于那些想要使用Angular来做这件事的人，这里有一个例子：|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4343316|首先需要一些库导入：(必须预先安装)|4343317|import+*+as+firebase+from+'firebase/app'
import+{+AngularFirestore,+AngularFirestoreCollection+}+from+'@angular/fire/firestore'|code-block|syntax|javascript|4343318|集合的一些配置：|4343319|yourCollection:+AngularFirestoreCollection;

constructor(
++++private+_db+:+AngularFirestore,
)+{+
++++//+this+is+your+firestore+collection
++++this.yourCollection+=+this._db.collection('collectionName');
}|4343320|下面是执行查询的方法：('products_id‘是一个is数组)|4343321|getProducts(products_ids)+{
++++var+queryId+=+firebase.firestore.FieldPath.documentId();
++++this.yourCollection.ref.where(queryId,+'in',+products_ids).get()
++++++++.then(({+docs+})+=>+{
++++++++++++console.log(docs.map(doc+=>+doc.data()))
++++++++})
}|4343322|entityMap^0|0|0|0|0|0|0|0^^$0|@$1|2|3|4|5|6|7|S|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|T|8|@]|9|@]|A|$]]|$1|D|3|E|5|F|7|U|8|@]|9|@]|A|$G|H]]|$1|I|3|J|5|6|7|V|8|@]|9|@]|A|$]]|$1|K|3|L|5|F|7|W|8|@]|9|@]|A|$G|H]]|$1|M|3|N|5|6|7|X|8|@]|9|@]|A|$]]|$1|O|3|P|5|F|7|Y|8|@]|9|@]|A|$G|H]]|$1|Q|3|-4|5|6|7|Z|8|@]|9|@]|A|$]]]|R|$]]

For the ones who want to do it using Angular, here is an example:
First some library imports are needed: (must be preinstalled)
<pre><code>import * as firebase from 'firebase/app'
import { AngularFirestore, AngularFirestoreCollection } from '@angular/fire/firestore'
</code></pre>
Some configuration for the collection:
<pre><code>yourCollection: AngularFirestoreCollection;

constructor(
 private _db : AngularFirestore,
) { 
 // this is your firestore collection
 this.yourCollection = this._db.collection('collectionName');
}
</code></pre>
Here is the method to do the query: ('products_id' is an Array of ids)
<pre><code>getProducts(products_ids) {
 var queryId = firebase.firestore.FieldPath.documentId();
 this.yourCollection.ref.where(queryId, 'in', products_ids).get()
 .then(({ docs }) =&gt; {
 console.log(docs.map(doc =&gt; doc.data()))
 })
}
</code></pre>

blocks|key|4343258|text|目前在Firestore中这似乎是不可能的。我不明白为什么Alexander的答案被接受，他提出的解决方案只返回"users“集合中的所有文档。|type|unstyled|depth|inlineStyleRanges|entityRanges|data|4343259|根据您需要做的事情，您应该考虑复制需要显示的相关数据，并仅在需要时才请求完整的文档。|4343260|entityMap^0|0|0^^$0|@$1|2|3|4|5|6|7|F|8|@]|9|@]|A|$]]|$1|B|3|C|5|6|7|G|8|@]|9|@]|A|$]]|$1|D|3|-4|5|6|7|H|8|@]|9|@]|A|$]]]|E|$]]

This doesn't seem to be possible in Firestore at the moment. I don't understand why Alexander's answer is accepted, the solution he proposes just returns all the documents in the "users" collection.

Depending on what you need to do, you should look into duplicating the relevant data you need to display and only request a full document when needed.

I am wondering if it's possible to get multiple documents by a list of ids in one round trip (network call) to the Firestore database.

Google Firestore - How to get several documents by multiple ids in one round-trip?

我想知道是否有可能在Firestore数据库的一次往返(网络调用)中通过I列表获取多个文档。

问Google Firestore -如何在一次往返中通过多个in获取多个文档？
EN

回答 11

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问Google Firestore -如何在一次往返中通过多个in获取多个文档？EN

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问Google Firestore -如何在一次往返中通过多个in获取多个文档？
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