Cloud Firestore provides powerful query functionality for specifying which documents you want to retrieve from a collection or collection group.

firestore unique id

After creating a query object, use the get function to retrieve the results:. See Get Data for more information on retrieving query results. You can also add a listener to a query to get the current results and listen for future updates. The where method takes three parameters: a field to filter on, a comparison operation, and a value. For iOS, Android, and Java, the comparison operator is explicitly named in the method.

You can use the array-contains operator to filter based on array values. For example:. If the array has multiple instances of the value you query on, the document is included in the results only once. An in query returns documents where the given field matches any of the comparison values.

This query returns every city document where the country field is set to USA or Japan. Similarly, use the array-contains-any operator to combine up to 10 array-contains clauses on the same field with a logical OR.

An array-contains-any query returns documents where the given field is an array that contains one or more of the comparison values:. Results from array-contains-any are de-duped. Even if a document's array field matches more than one of the comparison values, the result set includes that document only once.

Manage indexes in Cloud Firestore

Note the following limitations for in and array-contains-any :. You can also chain multiple where methods to create more specific queries logical AND. A collection group consists of all collections with the same ID. By default, queries retrieve results from a single collection in your database. Use a collection group query to retrieve documents from a collection group instead of from a single collection. For example, you can create a landmarks collection group by adding a landmarks subcollection to each city:.

We can use the simple and compound query described earlier to query a single city's landmarks subcollection, but you might also want to retrieve results from every city's landmarks subcollection at once.

The landmarks collection group consists of all collections with the ID landmarksand you can query it using a collection group query. For example, this collection group query retrieves all museum landmarks across all cities:. Before using a collection group query, you must create an index that supports your collection group query.Ever wondered about the magic behind Firebase's push IDs? If you're not familiar with Firebase's push IDs, they are the chronological, character unique IDs generated when you write lists of data to Firebase from any of our client libraries.

Below is an example of some data stored in Firebase by push ID:. We created push IDs for collaborative, multi-user applications to handle situations where many clients are adding to a list at the same time. We needed IDs that could be generated client-side so that they wouldn't need to wait for a round-trip to the server.

And we needed them to be unique so that many clients could append data to the same location at the same time without worrying about conflicts.

Push IDs are string identifiers that are generated client-side. They are a combination of a timestamp and some random bits. The timestamp ensures they are ordered chronologically, and the random bits ensure that each ID is unique, even if thousands of people are creating push IDs at the same time. A push ID contains bits of information. The first 48 bits are a timestamp, which both reduces the chance of collision and allows consecutively created push IDs to sort chronologically.

The timestamp is followed by 72 bits of randomness, which ensures that even two people creating push IDs at the exact same millisecond are extremely unlikely to generate identical IDs. One caveat to the randomness is that in order to preserve chronological ordering if a client creates multiple push IDs in the same millisecond, we just 'increment' the random bits by one.

There's one caveat to the chronological ordering of push IDs. Since the timestamp is generated client-side, it's at the mercy of the client's local clock, which could be incorrect.

When a Firebase client establishes a connection, the Firebase server sends an accurate timestamp to the client so it can use that to correct its incorrect clock when generating push IDs.

However, this correction only takes effect once the client has connected to Firebase, so if you generate a push ID before the client connects, we won't make an attempt to correct it. You could even generate two push IDs on the same client and the second push ID will be ordered before the first one if we started compensating for your clock between when you generated them. This guarantees chronological ordering, since the ServerValue.

We also get questions on whether developers can rely on push IDs to be unguessable by others, which can be important if you're trying to do security via unguessable Firebase paths.

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If you'd like to take a closer look at how push IDs work, we've published the code we use to generate them in a gist here. Have other questions about push IDs that weren't answered here? Let us know in our google group or by mentioning Firebase on Twitter, we'd love to hear your feedback! The Firebase Blog. About Firebase gives you the tools and infrastructure to build better apps and grow successful businesses. Learn more. Recent Posts.Cloud Firestore provides powerful query functionality for specifying which documents you want to retrieve from a collection or collection group.

After creating a query object, use the get function to retrieve the results:. See Get Data for more information on retrieving query results. You can also add a listener to a query to get the current results and listen for future updates. The where method takes three parameters: a field to filter on, a comparison operation, and a value.

For iOS, Android, and Java, the comparison operator is explicitly named in the method. You can use the array-contains operator to filter based on array values.

For example:. If the array has multiple instances of the value you query on, the document is included in the results only once. An in query returns documents where the given field matches any of the comparison values. This query returns every city document where the country field is set to USA or Japan. Similarly, use the array-contains-any operator to combine up to 10 array-contains clauses on the same field with a logical OR.

An array-contains-any query returns documents where the given field is an array that contains one or more of the comparison values:. Results from array-contains-any are de-duped. Even if a document's array field matches more than one of the comparison values, the result set includes that document only once. Note the following limitations for in and array-contains-any :. You can also chain multiple where methods to create more specific queries logical AND. A collection group consists of all collections with the same ID.

By default, queries retrieve results from a single collection in your database. Use a collection group query to retrieve documents from a collection group instead of from a single collection. For example, you can create a landmarks collection group by adding a landmarks subcollection to each city:.

firestore unique id

We can use the simple and compound query described earlier to query a single city's landmarks subcollection, but you might also want to retrieve results from every city's landmarks subcollection at once.

The landmarks collection group consists of all collections with the ID landmarksand you can query it using a collection group query. For example, this collection group query retrieves all museum landmarks across all cities:.

Before using a collection group query, you must create an index that supports your collection group query. You can create an index through an error message, the console, or the Firebase CLI. For the web and mobile SDKs, you must also create rules that allow your collection group queries. Cloud Firestore either does not support or provides limited support for the following types of queries:. Except as otherwise noted, the content of this page is licensed under the Creative Commons Attribution 4.

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Change your preferences any time. Stack Overflow for Teams is a private, secure spot for you and your coworkers to find and share information. This is covered in the documentation. See the last paragraph of the add a document section. You can do this in following manner code is for AngularFire2 v5, which is similar to any other version of firebase SDK say web, node etc.

This will generate a new document at Collection called projectsRef, with its id as pushKey and that document will have pushKey property same as id of document. But with. IDK if this helps, but I was wanting to get the id for the document from the Firestore database - that is, data that had already been entered into the console.

I wanted an easy way to access that ID on the fly, so I simply added it to the document object like so:. It doesn't work because the second statement executes before documentID is finished getting the document's ID. So, you have to wait for documentID to finish loading before you set the next document:. It's not the prettiest, but it is the only way to do what you are asking. This code is in Swift 5. This works for me. I update the document while in the same transaction. I create the document and immediately update the document with the document Id.

Learn more. Ask Question. Asked 2 years, 5 months ago. Active 2 months ago.Unlike a SQL database, there are no tables or rows. Instead, you store data in documentswhich are organized into collections.

Each document contains a set of key-value pairs. Cloud Firestore is optimized for storing large collections of small documents. All documents must be stored in collections. Documents can contain subcollections and nested objects, both of which can include primitive fields like strings or complex objects like lists. Collections and documents are created implicitly in Cloud Firestore. Simply assign data to a document within a collection. If either the collection or document does not exist, Cloud Firestore creates it.

In Cloud Firestore, the unit of storage is the document. A document is a lightweight record that contains fields, which map to values.

Each document is identified by a name. A document representing a user alovelace might look like this:. Complex, nested objects in a document are called maps. For example, you could structure the user's name from the example above with a map, like this:. You may notice that documents look a lot like JSON. In fact, they basically are. There are some differences for example, documents support extra data types and are limited in size to 1 MBbut in general, you can treat documents as lightweight JSON records.

Documents live in collections, which are simply containers for documents. For example, you could have a users collection to contain your various users, each represented by a document:. Cloud Firestore is schemaless, so you have complete freedom over what fields you put in each document and what data types you store in those fields.

Documents within the same collection can all contain different fields or store different types of data in those fields. However, it's a good idea to use the same fields and data types across multiple documents, so that you can query the documents more easily.This guide explains how to use the set, add, or update individual documents in Cloud Firestore. If you want to write data in bulk, see Transactions and Batched Writes. To create or overwrite a single document, use the set method:.

If the document does not exist, it will be created. If the document does exist, its contents will be overwritten with the newly provided data, unless you specify that the data should be merged into the existing document, as follows:. If you're not sure whether the document exists, pass the option to merge the new data with any existing document to avoid overwriting entire documents. Cloud Firestore lets you write a variety of data types inside a document, including strings, booleans, numbers, dates, null, and nested arrays and objects.

Cloud Firestore always stores numbers as doubles, regardless of what type of number you use in your code. Using Map or Dictionary objects to represent your documents is often not very convenient, so Cloud Firestore supports writing documents with custom classes. Cloud Firestore converts the objects to supported data types. Each custom class must have a public constructor that takes no arguments. In addition, the class must include a public getter for each property.

When you use set to create a document, you must specify an ID for the document to create. For example:. But sometimes there isn't a meaningful ID for the document, and it's more convenient to let Cloud Firestore auto-generate an ID for you. You can do this by calling add :. In some cases, it can be useful to create a document reference with an auto-generated ID, then use the reference later. For this use case, you can call doc :.

Behind the scenes. To update some fields of a document without overwriting the entire document, use the update method:. You can set a field in your document to a server timestamp which tracks when the server receives the update. If your document contains nested objects, you can use "dot notation" to reference nested fields within the document when you call update :.

Perform simple and compound queries in Cloud Firestore

Dot notation allows you to update a single nested field without overwriting other nested field. If you update a nested field without dot notation, you will overwrite the entire map field, for example:. If your document contains an array field, you can use arrayUnion and arrayRemove to add and remove elements.The Cloud Firestore is an awesome platform for quickly prototyping your app ideas into reality, however, it certainly comes with some limitations.

Currently, there is no way for you to enable uniqueness in field values in the whole database. There is a quick workaround, though with queries that you can use.

An app where users have their profiles and a unique username assigned to them. But, of course, there is a workaround. You can use Firestore queries to get the document ID which corresponds to the field you want to keep unique. Consider a sample usernames collection with and a few child documents.

Our database is set up such that each document corresponds to a single user profile data. To keep things simple, we will simply focus on keeping the username field unique in our database. Create a collection usernames containing a unique doc for each user. The doc-id of the document should be the username itself. When a user tries to sign up, check the usernames collection to see if a document with the id equal to the username that the user entered is available or not.

Since you have to get a doc, you need to give the clients access to the users collection. This may, or may not be a big deal for you, but if you are storing some sensitive data in the docs, this is a problem. Get the username from the user when they click signup after filling out their details. Send a GET request to the server with the username in the query parameter. In the usernames collection, check for a document with the id that is the username from the query parameter. As you can see, this code is pretty simple.

It checks the document with the id that is the username that you want to check. On your client, you need to check what the response for this request is. And, based on that, you can decide whether to sign up the user. Home contact archives privacy policy Previous post Next post Back to top Share post. The Problem 2.

Use Case 3. The Workaround 4. Creating User With Cloud Functions. The Problem You want to enforce uniqueness for a field value in your Firestore database for your app. Use Case An app where users have their profiles and a unique username assigned to them. The Workaround You can use Firestore queries to get the document ID which corresponds to the field you want to keep unique.

The simplest approach for this is this: Create a collection usernames containing a unique doc for each user. If the doc existsthe username is taken. Else, allow signup. Well… There is a problem with this approach. So, how do you fix this issue?

firestore unique id

Here comes the savior of the day: The Firebase Cloud Functions.


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