I've seen the firefeed example, but unfortunately it's a little lacking in functionality and I'm not sure how to move forward.
Given a data structure of users and posts:
{
"posts":
"12": {
"uid": 14,
"message": "This is my message #16 #55"
"timestamp": 1459361875666
"mentions": {
0: 16,
1: 55
}
}
"13": {
"uid": 55,
"message": "This is another message"
"timestamp": 1469861245622,
"mentions": null
}
}
"users": {
"14": {
"following": {
1: 16,
2: 55
}
}
"16": {
"following": {
0: 55
}
}
"55": {
"following": {
0: 14
}
}
}
}
How would I construct the query to bring back all the posts for users I'm following, as well as the posts I'm mentioned in? I can't find any recent documentation on advanced queries...
For example, if I am user 16, I should see all posts by user 55 (a user I am following) PLUS the post (id 12) by user 14 since they mentioned me in descending timestamp order.
Should I rethink the way the data is structured for performance purposes?
Any help would be greatly appreciated.
EDIT: restructured IDs to be unique
all the posts for users I'm following
// Reference
var ref = firebase.database().ref("users").child("some-user").child("following");
// Data call
ref.once("value).then(function(snapshot) {
// Iterate each following
snapshot.forEach(function(childSnapshot) {
// value
var childData = childSnapshot.val();
var followRef = firebase.database().ref("posts").orderByChild("uid").equalTo(i);
followRef.once("value").then(function(grandChildSnapshot) {
// RETURN OF ALL POSTS
}
});
});
Objects must have unique keys inside so for your data structure make sure they're not all called post, I recommend using push() and they would all get unique ids.
posts I'm mentioned in?
"users": {
"user": {
"id": 14,
"following": {
1: 16,
2: 55
},
mentioned: {
some-post: the-user,
...
}
}
...
You can keep your data structure the way it is, but also add to each follower the posts he is mentioned in.
// When post is pushed, get all users mentioned
...
var ref = firebase.database().ref("users").child(some-mentioned-user).child("mentioned");
ref.update({ <some-post> : <user-who-posted> });
After
var mentionedRef = firebase.database().ref("users").child(some-mentioned-user).child("mentioned");
mentionedRef.once("value").then(function(snapshot) {
// Iterate each following
snapshot.forEach(function(childSnapshot) {
// key
var childKey = childSnapshot.key();
var postRef = firebase.database().ref("posts").child(childKey);
postRef.once("value").then(function(grandChildSnapshot) {
// RETURN OF ALL POSTS
})
});
});
Comment with any questions.
Related
I have a collection users like this:
[{
'uid' : '1',
'favourites' : [
{ // fav1 },
{ // fav2 },
{ // fav3 },
etc
]
},
{
'uid' : '2',
'favourites' : [
{ // fav1 },
{ // fav2 },
{ // fav3 },
etc
]
},
etc
]
In some situations I have to update the favourites collection with a new "fav" and I can do that in this way:
final doc = FirebaseFirestore.instance.collection('users').doc(userId);
doc.update({ 'favourites': FieldValue.arrayUnion([fav.toJson()]) });
however the item might be not there so I have to use doc.set to create a new item. As I am new with Firebase, what is a "best practice" for a problem like this (if the element is not there create it first, otherwise update it)?
You can specify a merge option to set, which does precisely what you want:
doc.set({ 'favourites': FieldValue.arrayUnion([fav.toJson()]) }, SetOptions(merge : true))
You can use a function that can check if there is a doc or not with that specific info. And you can create a if-else statement depends on if there is a doc named like that or not.
An example function for checking the doc:
Future<bool> checkIfDocExists(String stuffID) async {
try {
/// Check If Document Exists
// Get reference to Firestore collection
var collectionRef = FirebaseFirestore.instance
.collection('favorites');
var doc = await collectionRef.doc(userId).get();
return doc.exists;
} catch (e) {
throw e;
}
}
I just want to Publish the relational Data for a Publication to client, but the issue is my Relational Data field is array of ID's of a Different Collection, I tried Different Packages but all works with single Relational ID but not working with Array of relational ID's, let assume I have two Collection Companies and Meteor.users below is my Company Document Looks like
{
_id : "dYo4tqpZms9j8aG4C"
owner : "yjzakAgYWejmJcuHz"
name : "Labbaik Waters"
peoples : ["yjzakAgYWejmJcuHz", "yjzakAgYWejmJcuHz"],
createdAt: "2019-09-18T15:33:29.952+00:00"
}
here you can see peoples field contains the user ID's as Array, so How I publish this userId's as user Documents, as for example I tried the most popular meteor package named publishComposit, when I tried Loop in Children's find, I got undefined in children i.e below
publishComposite('compoundCompanies', {
find() {
// Find top ten highest scoring posts
return Companies.find({
owner: this.userId
}, {sort: {}});
},
children: [
{
find(company) {
let cursors = company.peoples.forEach(peopleId => {
console.log(peopleId)
return Meteor.users.find(
{ _id: peopleId },
{ fields: { profile: 1 } });
})
//here cursor undefined
console.log(cursors)
return cursors
}
}
]
});
and if I implement async loop in children's find I got error like below code
publishComposite('compoundCompanies', {
find() {
// Find top ten highest scoring posts
return Companies.find({
owner: this.userId
}, {sort: {}});
},
children: [
{
async find(company) {
let cursors = await company.peoples.forEach(peopleId => {
console.log(peopleId)
return Meteor.users.find(
{ _id: peopleId },
{ fields: { profile: 1 } });
})
//here cursor undefined
console.log(cursors)
return cursors
}
}
]
});
the error occured in above code is Exception in callback of async function: TypeError: this.cursor._getCollectionName is not a function
I don't know what I am exactly doing wrong here, or implementing package function not as intended any help will be greatly appropriated
EDIT: my desired result should be full user documents instead of ID no matter it mapped in same peoples array or as another fields I just want as below
{
_id: "dYo4tqpZms9j8aG4C",
owner: "yjzakAgYWejmJcuHz",
name: "Labbaik Waters",
peoples: [
{
profile: {firstName: "Abdul", lastName: "Hameed"},
_id: "yjzakAgYWejmJcuHz"
}
],
createdAt: "2019-09-18T15:33:29.952+00:00"
}
I ran into a similar problem couple of days ago. There are two problems with the provided code. First, using async; it's not needed and rather complicates things. Second, publishComposite relies on receiving one cursor not multiple within its children to work properly.
Below is a snippet of the code used to solve the problem I had, hopefully you can replicate it.
Meteor.publishComposite("table.conversations", function(table, ids, fields) {
if (!this.userId) {
return this.ready();
}
check(table, String);
check(ids, Array);
check(fields, Match.Optional(Object));
return {
find() {
return Conversation.find(
{
_id: {
$in: ids
}
},
{ fields }
);
},
children: [
{
find(conversation) {
// constructing one big cursor that entails all of the documents in one single go
// as publish composite cannot work with multiple cursors at once
return User.find(
{ _id: { $in: conversation.participants } },
{ fields: { profile: 1, roles: 1, emails: 1 } }
);
}
}
]
};
});
I have the following document structure:
ProductDocument {
_id: "a",
price: 12,
starredByUserIds: [
"user1id",
"user2id",
"user3id",
]
}
For security, I want to ensure that a given user cannot see the other user's starredByUserIds by performing a query through a client console.
i.e. user3 should only be able to see his own respective entry:
ProductDocument {
_id: "a",
price: 12,
starredByUserIds: [
"user3id",
]
}
whilst a non-logged-in user should only be able to see:
ProductDocument {
_id: "a",
price: 12,
starredByUserIds: [
]
}
I can't seem to define the right Publish command. I'd like to be able to do something like:
Meteor.publish('Products', function() {
return Products.find( {}, { fields: { starredByUserIds: this.userId }} );
})
but 'fields' doesn't accept/match arbitrary string values.
How can this be achieved?
I think the below query should answer your requirement:
Products.find({}, {starredByUserIds: {$elemMatch:{$eq:this.userId}});
Following snippet would work:
Meteor.publish('Products', function() {
return Products.find( {starredByUserIds: this.UserId}, { fields: { starredByUserIds: 0 }} );
})
Explanation:
Here the query selector starredByUserIds: this.UserId will return documents only which has current user's Id in its starredByUserIds array.
I'm omitting starredByUserIds array while sending it to the client, because you it will either contain the current user's Id if the user is logged in or empty if the user is not logged in, you can regenerate it.
With those security concerns, maybe you should change your data model and put the 'stars' in a different collection. If you don't want to do that, then you must change the code of your publish functions to something like this:
Meteor.publish('Products', function () {
return Products.find().fetch().map(function (product) {
if (this.userId && product.starredByUserIds.indexOf(this.userId) != -1) {
product.starredByUserIds = [this.userId];
} else {
product.starredByUserIds = [];
}
return product;
});
});
I'm building an app where I need to process 5k+ tasks in small batches. For that I have a queue of tasks that is stored in a Firebase. I'd like to be able to pull certain amount of tasks with empty status, update their status and write back.
Currently I don't see how I can pull data where a certain field is empty. Is it possible? If not, what would be the alternative solution?
UPDATED 02/12. Here is the data structure that I have:
{
"-KAMnc89C5Yi_ef18ewc" : {
"0": {
"url": "https://excample.com/url",
"status": "done"
},
"1": {
"url": "https://excample.com/url1"
},
"2": {
"url": "https://excample.com/ur2"
},
"3": {
"url": "https://excample.com/ur3"
}
}
And this is the query I'm using:
queueRef.orderByChild('status').equalTo(null).limitToFirst(1).once('value', function(snapshot) {
console.log(snapshot.val());
});
queueRef points to "-KAMnc89C5Yi_ef18ewc" from the data above.
I expect to get one object - "1", but instead I'm getting all of them. Is there something I'm missing?
Firebase doesn't allow you to store a property without a value. That simply means that the property doesn't exist.
Luckily this doesn't really matter too much, because this seems to work. Given this data structure:
{
"-KADbswYg3FiQF78mmUf": {
"name": "task1",
"status": "done"
},
"-KADbugr7QzTx0s93Fs0": {
"name": "task2"
},
"-KADbvKvBgiAXxnQvoBp": {
"name": "task3"
}
}
This works:
ref.orderByChild('status').equalTo(null).once('value', function(snapshot) {
console.log(snapshot.val());
})
This prints task2 and task3.
Use the DataSnapshot.exists()
This will returns true if this snapshot contains any data. If not it will return false. According to the documentation here. It is slightly more efficient than using snapshot.val() !== null.
With a data structure like this:
{
"girlfriend": {
"first": "Pamala",
"last": "Anderson"
}
}
And a firebase call like this:
var ref = new Firebase("https://myURL/girlfriend/Pamala");
ref.once("value", function(snapshot) {
var a = snapshot.exists();
// a === true
var b = snapshot.child("girlfriend").exists();
// b === true
var c = snapshot.child("girlfriend/first").exists();
// c === true
var d = snapshot.child("girlfriend/middle").exists();
// d === false (because there is no "name/middle" girlfriend in the data snapshot)
});
I have a pretty basic data structure
events
topics
I would like to be able to easily show (query)
what topics are owned by an event
what events cover a topics
what are the most popular topics this month
I am pretty comfortable with my events structure like
/events/880088/topics.json *
["Firebase", "Cloud"]
but I struggle with how to structure the /topics nodes. I partially get the idea of going with something like
/topics/Firebase
{"12345":true,"88088":true}
and then if when I update an events's topic collection I would have to iterate over all the /topics/ nodes and update /topics/{{topic}}/{{eventid}} to {true | null}. Which seems rather ham fisted.
ALSO, then I am still at a loss of how to query say, what are the topics covered by events this month.
Example JSBin from comments below http://jsbin.com/dumumu/edit?js,output
* I know, I know, arrays are evil, https://www.firebase.com/blog/2014-04-28-best-practices-arrays-in-firebase.html, but I think they fit in this scenaris
Here's one way to add an event:
function addEvent(title, topics) {
var event =ref.child('events').push({ title: title });
topics.forEach(function(topic) {
event.child('topics').child(topic).set(true);
ref.child('topics').child(topic).child(event.key()).set(true);
});
}
Seems pretty simple for me. For an interesting twist, you can use the new multi-location updates we launched yesterday (September 2015):
function addEvent(title, topics) {
var updates = {};
var eventId = ref.push().key();
updates['events/'+eventId+'/title'] = title;
topics.forEach(function(topic) {
updates['events/'+eventId+'/topics/'+topic] = true;
updates['topic/'+topic+'/'+eventId] = true;
});
ref.update(updates);
}
The latter is a bit more code. But it's a single write operation to Firebase, so there's no chance of the user closing the app between write operations.
You invoke both the same of course:
addEvent('Learn all about Firebase', ['Firebase']);
addEvent('Cloudspin', ['Firebase', 'Google', 'Cloud']);
And the data structure becomes:
{
"events": {
"-K-4HCzj_ziHkZq3Fpat": {
"title": "Learn all about Firebase",
"topics": {
"Firebase": true
}
},
"-K-4HCzlBFDIwaA8Ajb7": {
"title": "Cloudspin",
"topics": {
"Cloud": true,
"Firebase": true,
"Google": true
}
}
},
"topic": {
"Cloud": {
"-K-4HCzlBFDIwaA8Ajb7": true
},
"Firebase": {
"-K-4HCzj_ziHkZq3Fpat": true,
"-K-4HCzlBFDIwaA8Ajb7": true
},
"Google": {
"-K-4HCzlBFDIwaA8Ajb7": true
}
}
}
Querying/reporting
With Firebase (and most NoSQL databases), you typically have to adapt your data structure for the reporting you want to do on it.
Abe wrote a great answer on this recently, so go read that for sure: Firebase Data Structure Advice Required
Update: change the topics for an event
If you want to change the topics for an existing event, this function is once way to accomplish that:
function updateEventTopics(event, newTopics) {
newTopics.sort();
var eventId = event.key();
var updates = {};
event.once('value', function(snapshot) {
var oldTopics = Object.keys(snapshot.val().topics).sort();
var added = newTopics.filter(function(t) { return oldTopics.indexOf(t) < 0; }),
removed = oldTopics.filter(function(t) { return newTopics.indexOf(t) < 0; });
added.forEach(function(topic) {
updates['events/'+eventId+'/topics/'+topic] = true;
updates['topic/'+topic+'/'+eventId] = true;
});
removed.forEach(function(topic) {
updates['events/'+eventId+'/topics/'+topic] = null;
updates['topic/'+topic+'/'+eventId] = null;
});
ref.update(updates);
});
}
The code is indeed a bit long, but that's mostly to determine the delta between the current topics and the new topics.
In case you're curious, if we run these API calls now:
var event = addEvent('Cloudspin', Date.now() - month, ['Firebase', 'Google', 'Cloud']);
updateEventTopics(event, ['Firebase', 'Google', 'GCP']);
The changeEventTopics() call will result in this update():
{
"events/-K-93CxuCrFDxM6k0B14/topics/Cloud": null,
"events/-K-93CxuCrFDxM6k0B14/topics/GCP": true,
"topic/Cloud/-K-93CxuCrFDxM6k0B14": null,
"topic/GCP/-K-93CxuCrFDxM6k0B14": true
}