I thought I read that you can query subcollections with the new Firebase Firestore, but I don't see any examples. For example I have my Firestore setup in the following way:
Dances [collection]
danceName
Songs [collection]
songName
How would I be able to query "Find all dances where songName == 'X'"
Update 2019-05-07
Today we released collection group queries, and these allow you to query across subcollections.
So, for example in the web SDK:
db.collectionGroup('Songs')
.where('songName', '==', 'X')
.get()
This would match documents in any collection where the last part of the collection path is 'Songs'.
Your original question was about finding dances where songName == 'X', and this still isn't possible directly, however, for each Song that matched you can load its parent.
Original answer
This is a feature which does not yet exist. It's called a "collection group query" and would allow you query all songs regardless of which dance contained them. This is something we intend to support but don't have a concrete timeline on when it's coming.
The alternative structure at this point is to make songs a top-level collection and make which dance the song is a part of a property of the song.
UPDATE
Now Firestore supports array-contains
Having these documents
{danceName: 'Danca name 1', songName: ['Title1','Title2']}
{danceName: 'Danca name 2', songName: ['Title3']}
do it this way
collection("Dances")
.where("songName", "array-contains", "Title1")
.get()...
#Nelson.b.austin Since firestore does not have that yet, I suggest you to have a flat structure, meaning:
Dances = {
danceName: 'Dance name 1',
songName_Title1: true,
songName_Title2: true,
songName_Title3: false
}
Having it in that way, you can get it done:
var songTitle = 'Title1';
var dances = db.collection("Dances");
var query = dances.where("songName_"+songTitle, "==", true);
I hope this helps.
UPDATE 2019
Firestore have released Collection Group Queries. See Gil's answer above or the official Collection Group Query Documentation
Previous Answer
As stated by Gil Gilbert, it seems as if collection group queries is currently in the works. In the mean time it is probably better to use root level collections and just link between these collection using the document UID's.
For those who don't already know, Jeff Delaney has some incredible guides and resources for anyone working with Firebase (and Angular) on AngularFirebase.
Firestore NoSQL Relational Data Modeling - Here he breaks down the basics of NoSQL and Firestore DB structuring
Advanced Data Modeling With Firestore by Example - These are more advanced techniques to keep in the back of your mind. A great read for those wanting to take their Firestore skills to the next level
What if you store songs as an object instead of as a collection? Each dance as, with songs as a field: type Object (not a collection)
{
danceName: "My Dance",
songs: {
"aNameOfASong": true,
"aNameOfAnotherSong": true,
}
}
then you could query for all dances with aNameOfASong:
db.collection('Dances')
.where('songs.aNameOfASong', '==', true)
.get()
.then(function(querySnapshot) {
querySnapshot.forEach(function(doc) {
console.log(doc.id, " => ", doc.data());
});
})
.catch(function(error) {
console.log("Error getting documents: ", error);
});
NEW UPDATE July 8, 2019:
db.collectionGroup('Songs')
.where('songName', isEqualTo:'X')
.get()
I have found a solution.
Please check this.
var museums = Firestore.instance.collectionGroup('Songs').where('songName', isEqualTo: "X");
museums.getDocuments().then((querySnapshot) {
setState(() {
songCounts= querySnapshot.documents.length.toString();
});
});
And then you can see Data, Rules, Indexes, Usage tabs in your cloud firestore from console.firebase.google.com.
Finally, you should set indexes in the indexes tab.
Fill in collection ID and some field value here.
Then Select the collection group option.
Enjoy it. Thanks
You can always search like this:-
this.key$ = new BehaviorSubject(null);
return this.key$.switchMap(key =>
this.angFirestore
.collection("dances").doc("danceName").collections("songs", ref =>
ref
.where("songName", "==", X)
)
.snapshotChanges()
.map(actions => {
if (actions.toString()) {
return actions.map(a => {
const data = a.payload.doc.data() as Dance;
const id = a.payload.doc.id;
return { id, ...data };
});
} else {
return false;
}
})
);
Query limitations
Cloud Firestore does not support the following types of queries:
Queries with range filters on different fields.
Single queries across multiple collections or subcollections. Each query runs against a single collection of documents. For more
information about how your data structure affects your queries, see
Choose a Data Structure.
Logical OR queries. In this case, you should create a separate query for each OR condition and merge the query results in your app.
Queries with a != clause. In this case, you should split the query into a greater-than query and a less-than query. For example, although
the query clause where("age", "!=", "30") is not supported, you can
get the same result set by combining two queries, one with the clause
where("age", "<", "30") and one with the clause where("age", ">", 30).
I'm working with Observables here and the AngularFire wrapper but here's how I managed to do that.
It's kind of crazy, I'm still learning about observables and I possibly overdid it. But it was a nice exercise.
Some explanation (not an RxJS expert):
songId$ is an observable that will emit ids
dance$ is an observable that reads that id and then gets only the first value.
it then queries the collectionGroup of all songs to find all instances of it.
Based on the instances it traverses to the parent Dances and get their ids.
Now that we have all the Dance ids we need to query them to get their data. But I wanted it to perform well so instead of querying one by one I batch them in buckets of 10 (the maximum angular will take for an in query.
We end up with N buckets and need to do N queries on firestore to get their values.
once we do the queries on firestore we still need to actually parse the data from that.
and finally we can merge all the query results to get a single array with all the Dances in it.
type Song = {id: string, name: string};
type Dance = {id: string, name: string, songs: Song[]};
const songId$: Observable<Song> = new Observable();
const dance$ = songId$.pipe(
take(1), // Only take 1 song name
switchMap( v =>
// Query across collectionGroup to get all instances.
this.db.collectionGroup('songs', ref =>
ref.where('id', '==', v.id)).get()
),
switchMap( v => {
// map the Song to the parent Dance, return the Dance ids
const obs: string[] = [];
v.docs.forEach(docRef => {
// We invoke parent twice to go from doc->collection->doc
obs.push(docRef.ref.parent.parent.id);
});
// Because we return an array here this one emit becomes N
return obs;
}),
// Firebase IN support up to 10 values so we partition the data to query the Dances
bufferCount(10),
mergeMap( v => { // query every partition in parallel
return this.db.collection('dances', ref => {
return ref.where( firebase.firestore.FieldPath.documentId(), 'in', v);
}).get();
}),
switchMap( v => {
// Almost there now just need to extract the data from the QuerySnapshots
const obs: Dance[] = [];
v.docs.forEach(docRef => {
obs.push({
...docRef.data(),
id: docRef.id
} as Dance);
});
return of(obs);
}),
// And finally we reduce the docs fetched into a single array.
reduce((acc, value) => acc.concat(value), []),
);
const parentDances = await dance$.toPromise();
I copy pasted my code and changed the variable names to yours, not sure if there are any errors, but it worked fine for me. Let me know if you find any errors or can suggest a better way to test it with maybe some mock firestore.
var songs = []
db.collection('Dances')
.where('songs.aNameOfASong', '==', true)
.get()
.then(function(querySnapshot) {
var songLength = querySnapshot.size
var i=0;
querySnapshot.forEach(function(doc) {
songs.push(doc.data())
i ++;
if(songLength===i){
console.log(songs
}
console.log(doc.id, " => ", doc.data());
});
})
.catch(function(error) {
console.log("Error getting documents: ", error);
});
It could be better to use a flat data structure.
The docs specify the pros and cons of different data structures on this page.
Specifically about the limitations of structures with sub-collections:
You can't easily delete subcollections, or perform compound queries across subcollections.
Contrasted with the purported advantages of a flat data structure:
Root-level collections offer the most flexibility and scalability, along with powerful querying within each collection.
I have a mongoose object which contains an array of ObjectIds, being used for population from another table. I want to be able to dedupe these. eg I have
[ '61e34f3293d9361bbb5883c7' ,'61e34f3293d9361bbb5883c7', '61e34f3293d9361bbb5883c7' ]
When i print and iterate through these they look like strings.
But they also have an _id property, so I think they're somehow "populated" or at least contain references to the child table.
What's the best way to do this? I tried:
const uniqueTokens = _.uniqBy(tokens, '_id') which doesn't seem to work as _id is some kind of Object.
converting to a string will allow me to dedupe:
const tokens = this.tokens || []
let newTokens: string[] = []
for (let t of tokens) {
const text = t.toString()
// clog.info('t', t, t._id, typeof t._id)
if (!newTokens.includes(text)) {
newTokens.push(text)
}
}
but then these aren't real Objects I can assign back to the original parent object.
// this.tokens = newTokens
await this.save()
I could maybe go through and re-find the objects, but that seems to be digging deeper into the hole!
Seems there must be a better way to handle these type of types...
related searches
How to compare mongoDB ObjectIds & remove duplicates in an array of documents using node.js?
I also tried using lean() on the tokens array to try and convert it back to a simple list of references, in case somehow the 'population' could be undone to help.
I'm down to creating a unique signature field for the referenced items and de-duping based on that.
In Mongoose, I can use a query populate to populate additional fields after a query. I can also populate multiple paths, such as
Person.find({})
.populate('books movie', 'title pages director')
.exec()
However, this would generate a lookup on book gathering the fields for title, pages and director - and also a lookup on movie gathering the fields for title, pages and director as well. What I want is to get title and pages from books only, and director from movie. I could do something like this:
Person.find({})
.populate('books', 'title pages')
.populate('movie', 'director')
.exec()
which gives me the expected result and queries.
But is there any way to have the behavior of the second snippet using a similar "single line" syntax like the first snippet? The reason for that, is that I want to programmatically determine the arguments for the populate function and feed it in. I cannot do that for multiple populate calls.
After looking into the sourcecode of mongoose, I solved this with:
var populateQuery = [{path:'books', select:'title pages'}, {path:'movie', select:'director'}];
Person.find({})
.populate(populateQuery)
.execPopulate()
you can also do something like below:
{path:'user',select:['key1','key2']}
You achieve that by simply passing object or array of objects to populate() method.
const query = [
{
path:'books',
select:'title pages'
},
{
path:'movie',
select:'director'
}
];
const result = await Person.find().populate(query).lean();
Consider that lean() method is optional, it just returns raw json rather than mongoose object and makes code execution a little bit faster! Don't forget to make your function (callback) async!
This is how it's done based on the Mongoose JS documentation http://mongoosejs.com/docs/populate.html
Let's say you have a BookCollection schema which contains users and books
In order to perform a query and get all the BookCollections with its related users and books you would do this
models.BookCollection
.find({})
.populate('user')
.populate('books')
.lean()
.exec(function (err, bookcollection) {
if (err) return console.error(err);
try {
mongoose.connection.close();
res.render('viewbookcollection', { content: bookcollection});
} catch (e) {
console.log("errror getting bookcollection"+e);
}
//Your Schema must include path
let createdData =Person.create(dataYouWant)
await createdData.populate([{path:'books', select:'title pages'},{path:'movie', select:'director'}])
I want to get a list of people that have the same tags as the user.
For that I need to use a react native fetch and the entity framework.
I also tried some raw sql with EF, but couldn't make it work, just don't know how.
I have two fetches. Both return a typical JSON object array. So I'm doing this:
var users = db.Users
.Include("TagUsers")
.Where(u => u.TagUsuario.Any(t => tags.Contains(t.idTag))).ToList();
The tags variable is an object array from a React Native Fetch, which in my C# function is of the type IList<>long.
The problem is that if this array have one element, like this const tags = [1]; or from the fetch like this
{0}
Tags:
idTag: 1
Name: "MyTag"
I can return the people with this tag, but if I do like this const tags = [1, 2]; or
{0}
Tags:
idTag: 1
Name: "MyTag"
{1}
Tags:
idTag: 2
Name: "AnotherTag"
It returns nothing on my LINQ request.
But if I do something like this on my C# function:
IList<>long tags = new List<>long();
tags.Add(1);
tags.Add(2);
It works perfectly.
The problem here is that the object array from the fetch is not "compatible" with the LINQ statement (Any, Contains). So I am in search of an alternative.
What do I have to do?
Change the IList parameter? I'm using that because accepts null without crashing.
Change the LINQ?
Use Raw SQL?
Maybe some conversion to get only an int array with the tags, not an object one.
Thanks for any tips and solutions.
Can you try to get the idTags from tags and use it as below.
var idTags = tags.Select(t => t.idTag);
var users = db.Users
.Include("TagUsers")
.Where(u => u.TagUsuario.Any(t => idTags.Contains(t.idTag))).ToList();
Is there any way to on Firebae to filter data in an array?
I have this model on my Firebase:
-KABIGeWnBMUKjLTcvp8
deviceToken:"7DE60240CB4B712F05A009F32358610C1327917E7E68409..."
favorites
0:"Masha"
1:"moksha"
name:"juan"
And the problem is that I can't find any method to get all "users" that contain a certain value on the "favorites" array field.
Nope, that's not an option See firebase equivalent to sql where in ().
Instead: invert your data structure to make this query possible:
items_by_favorites
"Masha"
"-KABIGeWnBMUKjLTcvp8"
"moksha"
"-KABIGeWnBMUKjLTcvp8"
Now you can look up the item keys for Masha with a simple read: ref.child('items_by_favorites/Masha') and then load each item:
ref.child('items_by_favorites/Masha').on('value', function(snapshot) {
snapshot.forEach(function(childSnapshot) {
var key = childSnapshot.key();
ref.child('items').child(key).once('value', function(itemSnapshot) {
console.log(itemSnapshot.val());
});
});
})
First of all your question is answered deep in the guide for retrieving data, which is where I got this answer. It's under complex queries, then range queries, should you want more info.
var ref = new Firebase("https://dinosaur-facts.firebaseio.com/dinosaurs");
ref.orderByChild("height").equalTo(25).on("child_added", function(snapshot) {
console.log(snapshot.key());
});
The basic idea is that you need to first order the reference by a common child value, and then call .equalTo() to end up with a query that yields what you want.
Also you can call order by child like
ref.orderByChild("height/sublevel")
To drill deeper in the tree.
FirebaseFirestore.instance.collection('your collection name').where('favorite', arrayContains: 'Masha').snapshot();