I'd like to query my database so that it returns Distinct Value of the chosen field. (Like SELECT DICTINCT) in MySQL.
Example: I queried my firstore Collection to get Documents where field messageTo isEqualTo 'Terry', this works fine but returns multiple documents with the same field 'chatID'.
I'd like to query the Collection to return Documents where field messageTo isEqualTo 'Terry' and making 'ChatID' field as DISTINCT value.
Firestore doesn't have anything that's equivalent to "select distinct". You will have to make a decision on the client by looking at the returned documents from a query.
It's worth noting, in a more general sense, that Firestore also does not offer any sort of projection view of documents when using client app APIs. Distinct selection is effectively a projection, because it only returns certain fields. Firestore document fetches and queries always return all the fields in a document.
Related
I use this code to get a collection snapshot from Firestore.
firestore().collection('project').where('userID', '==', authStore.uid).onSnapshot(onResult, onError);
This returns a huge amount of data, but I only need a few fields. Is it possible to query only a specific field? For example, if I only need the projectName and the creationDate fields.
Is it possible to query only a specific field?
No, that is not possbile. A Firestore listener fires on the document level. This means that you'll always get the entire document.
For example if I only need the projectName and the creationDate fields.
You cannot only get the value of a specific set of fields. It's the entire document or nothing. If you, however, only need to read those values and nothing more, then you should consider storing them in a separate document. This practice is called denormalization, and it's a common practice when it comes to NoSQL databases.
You might also take into consideration using the Firebase Realtime Database, for the duplicated data.
I am building a search bar that retrieve documents from firestore that matches a string value. What I want is not retrieve documents that I have retrieved before, which are stored in a Set<documents>.
Is that possible in Firestore?
I think you're looking for the not-in clause, which allows you to specify values not to retrieve. If you want to do this based on the document ID, you can specify FieldPath.documentId() for the field name.
I have the following structure in a Firestore collection. The "ranks" collection is updated with documents named after the timestamps. In each document, I have the same fields and values. How can I query all documents for a specific field without parsing the entire document? I.e. I want all values in all documents where field is "aave"?
I am new to Firestore and I've been trying this for several weeks now. I tried limiting with where and considered using sub collection group queries but in my case data is not stored in sub collections. Sorry, for not being able to provide more context, since I couldn't get much closer.
Queries select specific values, or ranges of values, of a known field. There is no support for dynamic field names in a query in Firestore.
But if you want to get all documents where the field aave exists/has any value, you can make use of the fact that in the sort order of values they always start with null. So to get all documents where the field aave exists/has any value, you could do:
firebase.firebase().collection("ranks").where("aave", ">=", null)
I have an Orders collection. It contains a field called venueId. And I'm querying against this field using isEqualTo. The venueId is the firebase user uid. I also have a venues collection. It contains this venueId and also has a list of VenueAdmins ids(These ids are also firebase user uids )The app is a point of sales app(pos). I need to query the orders collections so that valueAdmins and venueId see the correct stream. Is quite easy to query with venueId.. venueId,isEqualto, uid. I'm wondering what's the best approach to allow the venueAdmins see the stream as well.
|-Orders // collection
order. //doc
venueId:'2344567788999999'
|-Venues // collection
venue. //doc
venueAdmin: ['3333333333333','55555555555555555']
venueId:'2344567788999999'
My query builder so far: queryBuilder: (query) => query.where('venue.id', isEqualTo: uid)
Firestore does not have the capability to "join" documents from different collections in a single query. A single query can only consider documents in single collection at a time. The way you have your data structured now, it will require at least two queries. First, to find a venue, then second, to find the orders for an admin in a venue.
The only way to make this easier from the perspective of queries is to denormalize your data by duplicating venue data into the order documents. If each order also had a list of admins, then you could reduce this down to a single query.
So few day ago I moved my apps posts to cloud firestore from realtime database because of the more flexable querying that firestore apparently has. I have been modifying my code to work with firestore as the new database. Now I ran into a problem. How can I retrieve every document within "Posts" collection that has "Likes" collection that contains a specifically named document? I don't know if that makes sense so here's an image showcasing the problem:
I had a working query for firebase realtime database but can't figure out how to do it with firestore. Is it possible or do I have to change the structure of my database? If I do have to change the structure, what would be the most convenient way of getting the same result?
This is currently not possible with collection group queries. You might be tempted to put a filter on the query for FieldPath.documentId() == 'your-doucment-id', but that just isn't supported. FieldPath.documentId() is actually a token that refers to to fully unique document id, which includes the entire path of the document.
The workaround is to store the document ID as a field in the document, and filter on the contents of that field instead. So, if the document had a field called id with the ID of the document, you could query for collectionGroup("Likes").whereEquals('id', 'your-document-id').