How to get value of some field in firebase firestore android?

Question

Like upper question, i want to get value of some field in firebase firestore instead of all document with DocumentSnapshot

like this in SQL SELECT col_1, col_2, col_3 FROM table_name

How can i do it?

Thank you for the help.

Share us your database structure.. – Alex Mamo Nov 24 '17 at 08:21 — Alex Mamo, Nov 24 '17 at 08:21

Frank van Puffelen · Accepted Answer · 2021-11-06T13:52:58.360

28

The Cloud Firestore client-side SDKs always read and returns full documents. There is no way to read a subset of the fields in a document.

You can retrieve the entire document, and then process the DocumentSnapshot to just use the fields you're interested. But this means you're using more bandwidth than needed. If this is a regular occurrence for your app, consider creating a secondary collection where each document contains just the fields you're interested in.

Also see Doug's answer here (for Swift): How to access a specific field from Cloud FireStore Firebase in Swift

edited Nov 06 '21 at 13:52

answered Nov 24 '17 at 16:57

Frank van Puffelen

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yeah but this way I do not know what of a `DocumentSnapshot` has been modified! – Lamberto Basti May 04 '18 at 07:48
@Frank Regarding the bandwidth issue you mentioned, If I query for a document with multiple sub-collections (/nested sub-collections), will firestore return the document along with the documents of the sub-collections ? – Prasanna Kumar Dec 05 '20 at 12:42
Firestore queries are shallow. They don't return documents from subcollections. – Frank van Puffelen Dec 05 '20 at 15:21

score 4 · Answer 2 · answered Mar 16 '18 at 09:22

4

Firestore can read single field value. Firebase guides looks like didn't show these simple method.

For example:

[android]

String value = document.getString("col_1");


[node.js]

const value = doc.data().col_1

answered Mar 16 '18 at 09:22

Mike Yan

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2

Thanks @Mike Yan it works. Really strange that Firebase guide did not include it. – Ovais Chaudhry Apr 05 '18 at 09:00
3

you're still reading the entire document from Firestore, if that matters. You are consuming the bandwidth of the full document with this read on the client. – regretoverflow Nov 02 '18 at 03:18
Yes, but at least the client need not loop through the whole document to get 1 single field data. – Mike Yan Nov 02 '18 at 04:40
Animal animal = document.toObject(Animal); then animal.getName() or in js const animal = document.data(); then animal.name, use models! – cutiko Mar 30 '19 at 14:44

score 0 · Answer 3 · answered Apr 23 '22 at 04:56

0

Firebase allows a few ways to query like an RDBMS database. And these are very handy too. Try the Where clause. It returns a single document but u can add multiple filters. check for more

answered Apr 23 '22 at 04:56

Sanat Kumar

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score -2 · Answer 4 · answered Sep 15 '18 at 05:57

-2

try this code:

//set a global variable
dataList: Array<any>;


const dataCollection = firebase.firestore().collection('data');
dataCollection.get(query => {
query.forEach(docs => {
this.dataList.push({id: doc.id, data:doc.data()});
  })
})

answered Sep 15 '18 at 05:57

Luis Fernando Hernandez

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How to get value of some field in firebase firestore android?

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