sorry for the noob question.
I'm trying to write the CRUD endpoints for a Friendship model, which holds two users' IDs.
To create a Friendship the first thing I want to do is check if there is already an instance of that model, which would hold both IDs in any given order, so I wrote:
Friendship.findOne.all({users: [user1.id, user2.id]})
.then(.....
But the server responds with a 500 error: Friendship.findOne.all is not a function
What would be the proper way to do this?
I am assuming that you want to check if both id records/documents are present in your collection or not so for that you use $in operator like this
Friendship.find({id: {$in : [user1.id, user2.id]} })
.then(.....
This will return an array of records if any of id records will be present. And it will return empty array if non of the id records will present in your db
Related
Here is my problem:
I have a firestore collection that has a number of documents. There are about 500 documents generated/updated every hour and saved to the collection.
I would like to query the collection and setup a real-time snapshot listener for a subset of document IDs, that are provided by the client.
I think maybe I could to something like this (this syntax is likely not correct...just trying to get a feel for if it's even possible...but isn't the "in" limited to an array of 10 items? ):
const subbedDocs = ["doc1","doc2","doc3","doc4","doc5"]
docsRef.where('docID', 'in', subbedDocs).onSnapshot((doc) => {
handleSnapshot(doc);
});
I'm sorry, that code probably doesn't make sense....I'm still trying to learn all the ins and outs of Firestore.
Essentially, what I am trying to do is take an array of ID's and setup a .onSnapshot listener for those ID's. This list of IDs could be upwards of 40-50 items. Is this even possible? I am trying to avoid just setting up a listener on the whole collection and filtering out things I am not "subscribed" too as that seems wasteful from a resources perspective.
If you have the doc IDs in your array (it looks like you have) you can loop over them and start a listener during that:
const subbedDocs = ["doc1", "doc2", "doc3", "doc4", "doc5"];
for (let i = 0; i < subbedDocs.length; i++) {
const docID = subbedDocs[i];
docsRef.doc(docID).onSnapshot((doc) => {
handleSnapshot(doc);
});
}
It would be better to listen to a query and all filtered docs at once. But if you want to listen to each of them with a explicit listener that would do the trick.
As you've discovered, Firestore's in operator only allows up to 10 entries in the array. I'm also guessing you've added the docID as a field in the document, since I don't believe 'docID references the actual documentid.
I would not take this approach, because of the 10-entry limitation. What I would do is, as the client is selecting documents to follow, set a field (same in each document) to a unique Id for the client, so your query completely avoids the limitation. You can allow an unlimited number of Client listeners (up to implementation limits of Firestore) if you add that client ID into an array (called something like "ListenerArray") [again, as the client is selecting them]. Your query would be more like:
docsRef.where('ListenerArray', 'array-contains', clientID).onSnapshot((doc) => {
handleSnapshot(doc);
})
array-contains checks a single value against all entries in a document array, without limit. Every client can mark any number of documents to subscribe to.
I have defined a model like
Class Orders(Document):
orderAmount = fields.FloatField()
cashbackAmount = fields.FloatField()
meta = {'strict': False}
I want to get all orders where (orderAmount - cashbackAmount value > 500). I am using Mongoengine and using that I want to perform this operation. I am not using Django Framework so I cannot use solutions of that.
Let's approach this if you had to do this without Mongoengine. You would start by dividing this problem into two steps
1) How to get the difference between two fields and output it as the new field?
2) How to filter all the documents based on that field's value?
You can see that it consists of several steps, so it looks like a great use case for the aggregation framework.
The first problem can be solved using addFields and subtract operators.
{$addFields: {difference: {$subtract: ["$a", "$b"]}}}
what can be translated into "for every document add a new field called difference where difference=a-b".
The second problem is a simple filtering:
{$match: {difference:{$gt: 500}}}
"give me all documents where difference field is greater than 500"
So the whole query in MongoDB would look like this
db.collectionName.aggregate([{$addFields: {difference: {$subtract: ["$a", "$b"]}}}, {$match: {difference:{$gt: 500}}}])
Now we have to translate it into Mongoengine. It turns out that there is aggregate method defined, so we can easily make small adjustments to make this query work.
Diff.objects.aggregate({"$addFields": {"difference": {"$subtract": ["$a", "$b"]}}}, {"$match": {"difference":{"$gt": 500}}})
As a result, you get CommandCursor. You can interact with that object or just convert it to the list, to get a list of dictionaries.
I was wondering whether someone could provide some advice on my cloudant query below. It is now taking upwards of 20 seconds to execute against a DB of 50,000 documents - I suspect I could be getting better speed than this.
The purpose of the query is to find all of my documents with the attribute "searchCode" equalling a specific value plus a further list of specific IDs.
Both searchCode and _id are indexed - any ideas why my query would be taking so long / what I could do to speed it up?
mydb.find({selector: {"$or":[{"searchCode": searchCode},{"_id":{"$in":idList}}]}}, function (err, result) {
if(!err){
fulfill(result.docs);
}
else{
console.error(err);
}
});
Thanks,
James
You could try doing separate calls for the queries
find me documents where the searchCode = 'some value'
find me documents whose ids match a list of ids
The first can be achieved with a find call and a query like so:
{ selector: {"searchCode": searchCode} }
The second can be achieved by hitting the databases's _all_docs endpoint, passing in the list of ids as a keys parameter e.g.
GET /db/_all_docs?keys=["a","b","c"]
You might find that running both requests in parallel and merging the results gives you better performance.
I come from MySQL world so mongo queries are a bit difficult to make considering I can't really make sense of mongo style queries. I am trying to make a query for finding a string. The problem is from my very primitive knowledge about mongodb queries, the query I made isn't working. I tried it in mongoose as well in mongo shell.
Schema:
mongoose.Schema({
doctorID : String,
patientIDList : Array // array of strings
});
Query Objective:
I want to find a doctor with doctorID and then look inside the patientIDList for an ID xxx. If the patientIDList doesn't contains xxx then add xxx in the list otherwise just add nothing.
Query:
The 2 queries I tried
MyModel.findOne({'doctorID':newAppointment.doctorID}, {'patientIDList' : newAppointment.patientID}, function(err){...});
MyModel.findOne({'doctorID': newAppointment.doctorID, 'patientIDList': newAppointment.patientID}, function(err){...});
What am I doing wrong? How can I make a query?
It's always a bit of challenge to switch from a SQL to NoSQL DB and other way around. What you are trying to do is check if a value exists in an array. If the array is a string array you can simply query for the value in array.
MyModel.findOne({doctorID : newAppointment.doctorID}, {patientIDList :newAppointment.doctorID}, function(err, res){
console.log(err, res);
})
Further read: https://docs.mongodb.com/manual/tutorial/query-documents/#match-an-array-element
Relevant Question: Find document with array that contains a specific value
I'm trying to do a 'findOne' operation in a model that has an array property and filter the results to only list the item if the string im searching is in that array.
Example:
var AppUser = server.loopback.getModel('AppUser');
AppUser.create({
"name":"juan"
"favoriteLetters":["a","b","c"]
},function(){
AppUser.findOne({where:{favoriteLetters:'a'}},function(error,appUser){
console.log(error,appUser);
});
});
So in this case i want to find a 'appUser' that has a favorite letter 'a'.
Thanks.
As far as I understood, possibility of such kind of a query depends on the underlying datasource and is not supported yet for relational DBs. But should be fine with memory storage or mongodb. More details and syntax for query is here: https://groups.google.com/d/msg/loopbackjs/8c8kw8EMiPU/yev3lsmrTFUJ
For anyone else who lands here, that query in your model is correct (for Mongo anyways).
{where:{favoriteLetters:'a'}
Reference:
Find document with array that contains a specific value