ValueChanges not returning all data.

[robert-king]

Version info

"@agm/core": "^1.0.0-beta.2",
"@angular/animations": "6.0.5",
"@angular/cdk": "^5.2.5",
"@angular/common": "6.0.5",
"@angular/compiler": "6.0.5",
"@angular/core": "6.0.5",
"@angular/forms": "6.0.5",
"@angular/http": "6.0.5",
"@angular/material": "^5.2.5",
"@angular/platform-browser": "6.0.5",
"@angular/platform-browser-dynamic": "6.0.5",
"@angular/router": "6.0.5",
"@angular/service-worker": "6.0.5",
"angular-instantsearch": "^2.0.2",
"angularfire2": "^5.0.0-rc.10",

return this.usersCollection.valueChanges().subscribe((users) => {
  console.log('got users', users);
})

I have two users, however it logs a users array of just one user, then after that, it logs an array with two users. This is dangerous because If I pipe valueChanges() to first() or take(1), then I will be missing content forever.

I assume this happens because one of the users is me, and since i've already logged in, my user record is in the cache, so it returns that while fetching the rest of the user collection. Perhaps that's expected behaviour, if so, then it should be better documented to be careful piping valueChanges to .first() or to .take(1)

[davideast]

@robert-king Can you create a stackblitz recreating the problem so I can debug?

[robert-king]

https://stackblitz.com/edit/angular-g4ppdt?file=src%2Fapp%2Fhello.component.ts

https://angular-g4ppdt.stackblitz.io/

[trentjones21]

I can confirm that this is a problem. It would be nice if there was a way to disable the cache completely for an individual query. Something like

db.collection('users').valueChanges({ source: 'server' });

This appears to be how it works when using firestore directly. I can't seem to find a way to do it with angularfire2 though. Here is the relevant firestore documentation:

https://firebase.google.com/docs/reference/js/firebase.firestore.GetOptions

var docRef = db.collection("cities").doc("SF");

// Valid options for source are 'server', 'cache', or
// 'default'. See https://firebase.google.com/docs/reference/js/firebase.firestore.GetOptions
// for more information.
var getOptions = {
    source: 'cache'
};

// Get a document, forcing the SDK to fetch from the offline cache.
docRef.get(getOptions).then(function(doc) {
    // Document was found in the cache. If no cached document exists,
    // an error will be returned to the 'catch' block below.
    console.log("Cached document data:", doc.data());
}).catch(function(error) {
    console.log("Error getting cached document:", error);
});

[robert-king]

It would be cool to show progress too - e.g. show some things quickly from the cache, but have a loading spinner to show while more results are being fetched from the server.

[mikhailmelnik]

Spent a few hours yesterday debugging same thing, ended up with the following snippet illustrating the issue:

afs.collection('profiles').valueChanges().pipe(take(1), tap(console.log)).subscribe(() =>
  afs.doc('profiles/SOME_ID').valueChanges().pipe(tap(console.log), delay(2000)).subscribe(() =>
    afs.collection('profiles').valueChanges().pipe(tap(console.log)).subscribe()));

with output [N], {...}, [1], [N] where N/1 is the reported collection length, so if I add take(1) to the last line which was my original intention I would never receive the full collection.

As a workaround started using underlying firestore which allows to set a source:

afs.firestore.collection('profiles').get({source: 'server'}).then(...)

Would be great to have a parameter for the valueChanges() call as @trentjones21 have suggested.

[TyagiAnkit40]

I have the same issue. Did anyone find a workaround on how to disable caching when using valuechanges or onSnapShot?

[davideast]

@robert-king @trentjones21 @TyagiAnkit40 Just put in a PR to address this. You can specify the { includeMetadataChanges: true } config and then filter out any snap.meta.fromCache: true objects.

Let me know if any of you are up for testing the test release.

[TyagiAnkit40]

I can test. Currently, I am using an ugly workaround by calling get directly inside get collection which I want to avoid.

this.db.collection('OrderBom', ref => {
let query : firebase.firestore.Query = ref;
query = query.where('orderNo', '==', orderNo).where('inEntityLC', '==', entity);
query.get({source: 'server'}).then(result=>{
var arr=[];
result.forEach((doc) => {
arr.push(doc.data());
});
this.createOrderTab(arr);
})
return query;
})

[TyagiAnkit40]

Will it be better if we can directly specify {source : 'server'} instead of reading metadata? That way, the subscribe to valuechanges / snapshot will only fire once. Today, subscribe fires two times, one for cached data and another for server data. Even today, I can look at 'fromCache' property and identify whether it's cached data or loaded from server. Not sure how including metadata will be different.

[davideast]

We will add the ability to filter client events with #1819. However, in the OP's use case you should not use .take(1) on a stream. Stream behave differently than a data request like a .get() call. If you need the set of data call ref.get().