Related
From the docs:
You can also chain multiple where() methods to create more specific queries (logical AND).
How can I perform an OR query?
Example:
Give me all documents where the field status is open OR upcoming
Give me all documents where the field status == open OR createdAt <= <somedatetime>
OR isn't supported as it's hard for the server to scale it (requires keeping state to dedup). The work around is to issue 2 queries, one for each condition, and dedup on the client.
Edit (Nov 2019):
Cloud Firestore now supports IN queries which are a limited type of OR query.
For the example above you could do:
// Get all documents in 'foo' where status is open or upcmoming
db.collection('foo').where('status','in',['open','upcoming']).get()
However it's still not possible to do a general OR condition involving multiple fields.
With the recent addition of IN queries, Firestore supports "up to 10 equality clauses on the same field with a logical OR"
A possible solution to (1) would be:
documents.where('status', 'in', ['open', 'upcoming']);
See Firebase Guides: Query Operators | in and array-contains-any
suggest to give value for status as well.
ex.
{ name: "a", statusValue = 10, status = 'open' }
{ name: "b", statusValue = 20, status = 'upcoming'}
{ name: "c", statusValue = 30, status = 'close'}
you can query by ref.where('statusValue', '<=', 20) then both 'a' and 'b' will found.
this can save your query cost and performance.
btw, it is not fix all case.
I would have no "status" field, but status related fields, updating them to true or false based on request, like
{ name: "a", status_open: true, status_upcoming: false, status_closed: false}
However, check Firebase Cloud Functions. You could have a function listening status changes, updating status related properties like
{ name: "a", status: "open", status_open: true, status_upcoming: false, status_closed: false}
one or the other, your query could be just
...where('status_open','==',true)...
Hope it helps.
This doesn't solve all cases, but for "enum" fields, you can emulate an "OR" query by making a separate boolean field for each enum-value, then adding a where("enum_<value>", "==", false) for every value that isn't part of the "OR" clause you want.
For example, consider your first desired query:
Give me all documents where the field status is open OR upcoming
You can accomplish this by splitting the status: string field into multiple boolean fields, one for each enum-value:
status_open: bool
status_upcoming: bool
status_suspended: bool
status_closed: bool
To perform your "where status is open or upcoming" query, you then do this:
where("status_suspended", "==", false).where("status_closed", "==", false)
How does this work? Well, because it's an enum, you know one of the values must have true assigned. So if you can determine that all of the other values don't match for a given entry, then by deduction it must match one of the values you originally were looking for.
See also
in/not-in/array-contains-in: https://firebase.google.com/docs/firestore/query-data/queries#in_and_array-contains-any
!=: https://firebase.googleblog.com/2020/09/cloud-firestore-not-equal-queries.html
I don't like everyone saying it's not possible.
it is if you create another "hacky" field in the model to build a composite...
for instance, create an array for each document that has all logical or elements
then query for .where("field", arrayContains: [...]
you can bind two Observables using the rxjs merge operator.
Here you have an example.
import { Observable } from 'rxjs/Observable';
import 'rxjs/add/observable/merge';
...
getCombinatedStatus(): Observable<any> {
return Observable.merge(this.db.collection('foo', ref => ref.where('status','==','open')).valueChanges(),
this.db.collection('foo', ref => ref.where('status','==','upcoming')).valueChanges());
}
Then you can subscribe to the new Observable updates using the above method:
getCombinatedStatus.subscribe(results => console.log(results);
I hope this can help you, greetings from Chile!!
We have the same problem just now, luckily the only possible values for ours are A,B,C,D (4) so we have to query for things like A||B, A||C, A||B||C, D, etc
As of like a few months ago firebase supports a new query array-contains so what we do is make an array and we pre-process the OR values to the array
if (a) {
array addObject:#"a"
}
if (b) {
array addObject:#"b"
}
if (a||b) {
array addObject:#"a||b"
}
etc
And we do this for all 4! values or however many combos there are.
THEN we can simply check the query [document arrayContains:#"a||c"] or whatever type of condition we need.
So if something only qualified for conditional A of our 4 conditionals (A,B,C,D) then its array would contain the following literal strings: #["A", "A||B", "A||C", "A||D", "A||B||C", "A||B||D", "A||C||D", "A||B||C||D"]
Then for any of those OR combinations we can just search array-contains on whatever we may want (e.g. "A||C")
Note: This is only a reasonable approach if you have a few number of possible values to compare OR with.
More info on Array-contains here, since it's newish to firebase docs
If you have a limited number of fields, definitely create new fields with true and false like in the example above. However, if you don't know what the fields are until runtime, you have to just combine queries.
Here is a tags OR example...
// the ids of students in class
const students = [studentID1, studentID2,...];
// get all docs where student.studentID1 = true
const results = this.afs.collection('classes',
ref => ref.where(`students.${students[0]}`, '==', true)
).valueChanges({ idField: 'id' }).pipe(
switchMap((r: any) => {
// get all docs where student.studentID2...studentIDX = true
const docs = students.slice(1).map(
(student: any) => this.afs.collection('classes',
ref => ref.where(`students.${student}`, '==', true)
).valueChanges({ idField: 'id' })
);
return combineLatest(docs).pipe(
// combine results by reducing array
map((a: any[]) => {
const g: [] = a.reduce(
(acc: any[], cur: any) => acc.concat(cur)
).concat(r);
// filter out duplicates by 'id' field
return g.filter(
(b: any, n: number, a: any[]) => a.findIndex(
(v: any) => v.id === b.id) === n
);
}),
);
})
);
Unfortunately there is no other way to combine more than 10 items (use array-contains-any if < 10 items).
There is also no other way to avoid duplicate reads, as you don't know the ID fields that will be matched by the search. Luckily, Firebase has good caching.
For those of you that like promises...
const p = await results.pipe(take(1)).toPromise();
For more info on this, see this article I wrote.
J
OR isn't supported
But if you need that you can do It in your code
Ex : if i want query products where (Size Equal Xl OR XXL : AND Gender is Male)
productsCollectionRef
//1* first get query where can firestore handle it
.whereEqualTo("gender", "Male")
.addSnapshotListener((queryDocumentSnapshots, e) -> {
if (queryDocumentSnapshots == null)
return;
List<Product> productList = new ArrayList<>();
for (DocumentSnapshot snapshot : queryDocumentSnapshots.getDocuments()) {
Product product = snapshot.toObject(Product.class);
//2* then check your query OR Condition because firestore just support AND Condition
if (product.getSize().equals("XL") || product.getSize().equals("XXL"))
productList.add(product);
}
liveData.setValue(productList);
});
For Flutter dart language use this:
db.collection("projects").where("status", whereIn: ["public", "unlisted", "secret"]);
actually I found #Dan McGrath answer working here is a rewriting of his answer:
private void query() {
FirebaseFirestore db = FirebaseFirestore.getInstance();
db.collection("STATUS")
.whereIn("status", Arrays.asList("open", "upcoming")) // you can add up to 10 different values like : Arrays.asList("open", "upcoming", "Pending", "In Progress", ...)
.addSnapshotListener(new EventListener<QuerySnapshot>() {
#Override
public void onEvent(#Nullable QuerySnapshot queryDocumentSnapshots, #Nullable FirebaseFirestoreException e) {
for (DocumentSnapshot documentSnapshot : queryDocumentSnapshots) {
// I assume you have a model class called MyStatus
MyStatus status= documentSnapshot.toObject(MyStatus.class);
if (status!= null) {
//do somthing...!
}
}
}
});
}
I need to create a view that lists the values for an attribute of a doc field.
Sample Doc:
{
"_id": "003e5a9742e04ce7a6791aa845405c17",
"title", "testdoc",
"samples": [
{
"confidence": "high",
"handle": "joetest"
}
]
}
Example using that doc, I want a view that will return the values for "handle"
I found this example with the heading - Get contents of an object with specific attributes e.g. doc.objects.[0].attribute. But when I fill in the attribute name, e.g. "handle" and replace doc.objects with doc.samples, I get no results:
Toggle line numbers
// map
function(doc) {
for (var idx in doc.objects) {
emit(doc.objects[idx], attribute)
}
}
That will create an array of key-value-pairs where the key is alway the value of handle. Replace null with a value you want e.g. doc.title. If you want to get the doc attached to every row use the query parameter ?include_docs=true while requesting the view.
// map
function (doc) {
var samples = doc.samples
for(var i = 0, sample; sample = samples[i++];) {
emit(sample.handle, null)
}
}
Like this ->
function(doc) {
for (var i in doc.samples) {
emit(doc._id, doc.samples[i].handle)
}
}
It will produce a result based on the doc._id field as the key. Or, if you want your key to be based on the .handle field you reverse the parameters in emit so you can search by startKey=, endKey=.
Is it possible to $addToSet and determine which items were added to the set?
i.e. $addToSet tags to a post and return which ones were actually added
Not really, and not with a single statement. The closest you can get is with the findAndModify() method, and compare the orginal document form to the fields that you submitted in your $addToSet statement:
So considering an initial document:
{
"fields": [ "B", "C" ]
}
And then processing this code:
var setInfo = [ "A", "B" ];
var matched = [];
var doc = db.collection.findAndModify(
{ "_id": "myid" },
{
"$addToSet": { "fields": { "$each": setInfo } }
}
);
doc.fields.forEach(function(field) {
if ( setInfo.indexOf(field) != -1 ) {
matched.push(field);
}
});
return matched;
So that is a basic JavaScript abstraction of the methods and not actually nodejs general syntax for either the native node driver or the Mongoose syntax, but it does describe the basic premise.
So as long as you are using a "default" implementation method that returns the "original" state of the document before it was modified the you can play "spot the difference" as it were, and as is shown in the code example.
But doing this over general "update" operations is just not possible, as they are designed to possibly affect one or more objects and never return this detail.
My collection is like this
{
"name":""
"type":""
"arr":[
{
"type":""
"other field"
...
},
{
"type":""
"other field"
...
}
}
and my condition is
input parameter is name.
so based on name i have to fetch document and one more condition is that type outside and inside the array should match..
Need to fetch those records alone..
How to achieve this
Bad performance, but just work (http://docs.mongodb.org/manual/reference/operator/where)
db.SOME_COLLECTION.find({
name:'SOME_VALUE',
$where:
function() {
for(var i = 0; i < obj.arr.length; i++) {
if(obj.arr[i].type==obj.type) {
return obj
}
}
}
}
)
p.s. aggregation framework has solved analogical problems, but in this case, imho, only $where clause available
If I understand you correctly, this is how you get the desired result
{name:"",type:"",arr.type:""}
you can put the desired values and it will return you all the matching record.
Consider following sample documents stored in CouchDB
{
"_id":....,
"rev":....,
"type":"orders",
"Period":"2013-01",
"Region":"East",
"Category":"Stationary",
"Product":"Pen",
"Rate":1,
"Qty":10,
"Amount":10
}
{
"_id":....,
"rev":....,
"type":"orders",
"Period":"2013-02",
"Region":"South",
"Category":"Food",
"Product":"Biscuit",
"Rate":7,
"Qty":5,
"Amount":35
}
Consider following SQL query
SELECT Period, Region,Category, Product, Min(Rate),Max(Rate),Count(Rate), Sum(Qty),Sum(Amount)
FROM Sales
GROUP BY Period,Region,Category, Product;
Is it possible to create map/reduce views in couchdb equivalent to the above SQL query and to produce output like
[
{
"Period":"2013-01",
"Region":"East",
"Category":"Stationary",
"Product":"Pen",
"MinRate":1,
"MaxRate":2,
"OrdersCount":20,
"TotQty":1000,
"Amount":1750
},
{
...
}
]
Up front, I believe #benedolph's answer is best-practice and best-case-scenario. Each reduce should ideally return 1 scalar value to keep the code as simple as possible.
However, it is true you'd have to issue multiple queries to retrieve the full resultset described by your question. If you don't have the option to run queries in parallel, or it is really important to keep the number of queries down it is possible to do it all at once.
Your map function will remain pretty simple:
function (doc) {
emit([ doc.Period, doc.Region, doc.Category, doc.Product ], doc);
}
The reduce function is where it gets lengthy:
function (key, values, rereduce) {
// helper function to sum all the values of a specified field in an array of objects
function sumField(arr, field) {
return arr.reduce(function (prev, cur) {
return prev + cur[field];
}, 0);
}
// helper function to create an array of just a single property from an array of objects
// (this function came from underscore.js, at least it's name and concept)
function pluck(arr, field) {
return arr.map(function (item) {
return item[field];
});
}
// rereduce made this more challenging, and I could not thoroughly test this right now
// see the CouchDB wiki for more information
if (rereduce) {
// a rereduce handles transitionary values
// (so the "values" below are the results of previous reduce functions, not the map function)
return {
OrdersCount: sumField(values, "OrdersCount"),
MinRate: Math.min.apply(Math, pluck(values, "MinRate")),
MaxRate: Math.max.apply(Math, pluck(values, "MaxRate")),
TotQty: sumField(values, "TotQty"),
Amount: sumField(values, "Amount")
};
} else {
var rates = pluck(values, "Rate");
// This takes a group of documents and gives you the stats you were asking for
return {
OrdersCount: values.length,
MinRate: Math.min.apply(Math, rates),
MaxRate: Math.max.apply(Math, rates),
TotQty: sumField(values, "Qty"),
Amount: sumField(values, "Amount")
};
}
}
I was not able to test the "rereduce" branch of this code at all, you'll have to do that on your end. (but this should work) See the wiki for information about reduce vs rereduce.
The helper functions I added at the top actually made the code overall much shorter and easier to read, they're largely influenced by my experience with Underscore.js. However, you can't include CommonJS modules in reduce functions, so it has to be written manually.
Again, best-case scenario is to have each aggregated field get it's own map/reduce index, but if that isn't on option to you, the above code should get you what you've described here in the question.
I will propose a very simple solution that requires one view per variable you want to aggregate in your "select" clause. While it is certainly possible to aggregate all variables in a single view, the reduce function would be far more complex.
The design document looks like this:
{
"_id": "_design/ddoc",
"_rev": "...",
"language": "javascript",
"views": {
"rates": {
"map": "function(doc) {\n emit([doc.Period, doc.Region, doc.Category, doc.Product], doc.Rate);\n}",
"reduce": "_stats"
},
"qty": {
"map": "function(doc) {\n emit([doc.Period, doc.Region, doc.Category, doc.Product], doc.Qty);\n}",
"reduce": "_stats"
}
}
}
Now, you can query <couchdb>/<database>/_design/ddoc/_view/rates?group_level=4 to get the statistics about the "Rate" variable. The result should look like this:
{"rows":[
{"key":["2013-01","East","Stationary","Pen"],"value":{"sum":4,"count":3,"min":1,"max":2,"sumsqr":6}},
{"key":["2013-01","North","Stationary","Pen"],"value":{"sum":1,"count":1,"min":1,"max":1,"sumsqr":1}},
{"key":["2013-01","South","Stationary","Pen"],"value":{"sum":0.5,"count":1,"min":0.5,"max":0.5,"sumsqr":0.25}},
{"key":["2013-02","South","Food","Biscuit"],"value":{"sum":7,"count":1,"min":7,"max":7,"sumsqr":49}}
]}
For the "Qty" variable, the query would be <couchdb>/<database>/_design/ddoc/_view/qty?group_level=4.
With the group_level property you can control over which levels the aggregation is to be performed. For example, querying with group_level=2 will aggregate up to "Period" and "Region".