Related
Is it possible to count how many items a collection has using the new Firebase database, Cloud Firestore?
If so, how do I do that?
2023 Update
Firestore now supports aggregation queries.
Node SDK
const collectionRef = db.collection('cities');
const snapshot = await collectionRef.count().get();
console.log(snapshot.data().count);
Web v9 SDK
const coll = collection(db, "cities");
const snapshot = await getCountFromServer(coll);
console.log('count: ', snapshot.data().count);
Notable Limitation - You cannot currently use count() queries with real-time listeners and offline queries. (See below for alternatives)
Pricing - Pricing depends on the number of matched index entries rather than the number of documents. One index entry contains multiple documents making this cheaper than counting documents individually.
Old Answer
As with many questions, the answer is - It depends.
You should be very careful when handling large amounts of data on the front end. On top of making your front end feel sluggish, Firestore also charges you $0.60 per million reads you make.
Small collection (less than 100 documents)
Use with care - Frontend user experience may take a hit
Handling this on the front end should be fine as long as you are not doing too much logic with this returned array.
db.collection('...').get().then(snap => {
size = snap.size // will return the collection size
});
Medium collection (100 to 1000 documents)
Use with care - Firestore read invocations may cost a lot
Handling this on the front end is not feasible as it has too much potential to slow down the users system. We should handle this logic server side and only return the size.
The drawback to this method is you are still invoking Firestore reads (equal to the size of your collection), which in the long run may end up costing you more than expected.
Cloud Function:
db.collection('...').get().then(snap => {
res.status(200).send({length: snap.size});
});
Front End:
yourHttpClient.post(yourCloudFunctionUrl).toPromise().then(snap => {
size = snap.length // will return the collection size
})
Large collection (1000+ documents)
Most scalable solution
FieldValue.increment()
As of April 2019 Firestore now allows incrementing counters, completely atomically, and without reading the data prior. This ensures we have correct counter values even when updating from multiple sources simultaneously (previously solved using transactions), while also reducing the number of database reads we perform.
By listening to any document deletes or creates we can add to or remove from a count field that is sitting in the database.
See the firestore docs - Distributed Counters
Or have a look at Data Aggregation by Jeff Delaney. His guides are truly fantastic for anyone using AngularFire but his lessons should carry over to other frameworks as well.
Cloud Function:
export const documentWriteListener = functions.firestore
.document('collection/{documentUid}')
.onWrite((change, context) => {
if (!change.before.exists) {
// New document Created : add one to count
db.doc(docRef).update({ numberOfDocs: FieldValue.increment(1) });
} else if (change.before.exists && change.after.exists) {
// Updating existing document : Do nothing
} else if (!change.after.exists) {
// Deleting document : subtract one from count
db.doc(docRef).update({ numberOfDocs: FieldValue.increment(-1) });
}
return;
});
Now on the frontend you can just query this numberOfDocs field to get the size of the collection.
Simplest way to do so is to read the size of a "querySnapshot".
db.collection("cities").get().then(function(querySnapshot) {
console.log(querySnapshot.size);
});
You can also read the length of the docs array inside "querySnapshot".
querySnapshot.docs.length;
Or if a "querySnapshot" is empty by reading the empty value, which will return a boolean value.
querySnapshot.empty;
As far as I know there is no build-in solution for this and it is only possible in the node sdk right now.
If you have a
db.collection('someCollection')
you can use
.select([fields])
to define which field you want to select. If you do an empty select() you will just get an array of document references.
example:
db.collection('someCollection').select().get().then(
(snapshot) => console.log(snapshot.docs.length)
);
This solution is only a optimization for the worst case of downloading all documents and does not scale on large collections!
Also have a look at this:
How to get a count of number of documents in a collection with Cloud Firestore
Aggregate count query just landed as a preview in Firestore.
Announced at the 2022 Firebase Summit: https://firebase.blog/posts/2022/10/whats-new-at-Firebase-Sumit-2022
Excerpt:
[Developer Preview] Count() function: With the new count function in
Firstore [sic], you can now get the count of the matching documents when you
run a query or read from a collection, without loading the actual
documents, which saves you a lot of time.
Code sample they showed at the summit:
During the Q&A, someone asked about pricing for aggregated queries, and the answer the Firebase team provided was that it'll cost 1 / 1000th of the price of a read (rounded up to the nearest read, see comments below for more details), but will count all records that are part of the aggregate.
Be careful counting number of documents for large collections. It is a little bit complex with firestore database if you want to have a precalculated counter for every collection.
Code like this doesn't work in this case:
export const customerCounterListener =
functions.firestore.document('customers/{customerId}')
.onWrite((change, context) => {
// on create
if (!change.before.exists && change.after.exists) {
return firestore
.collection('metadatas')
.doc('customers')
.get()
.then(docSnap =>
docSnap.ref.set({
count: docSnap.data().count + 1
}))
// on delete
} else if (change.before.exists && !change.after.exists) {
return firestore
.collection('metadatas')
.doc('customers')
.get()
.then(docSnap =>
docSnap.ref.set({
count: docSnap.data().count - 1
}))
}
return null;
});
The reason is because every cloud firestore trigger has to be idempotent, as firestore documentation say: https://firebase.google.com/docs/functions/firestore-events#limitations_and_guarantees
Solution
So, in order to prevent multiple executions of your code, you need to manage with events and transactions. This is my particular way to handle large collection counters:
const executeOnce = (change, context, task) => {
const eventRef = firestore.collection('events').doc(context.eventId);
return firestore.runTransaction(t =>
t
.get(eventRef)
.then(docSnap => (docSnap.exists ? null : task(t)))
.then(() => t.set(eventRef, { processed: true }))
);
};
const documentCounter = collectionName => (change, context) =>
executeOnce(change, context, t => {
// on create
if (!change.before.exists && change.after.exists) {
return t
.get(firestore.collection('metadatas')
.doc(collectionName))
.then(docSnap =>
t.set(docSnap.ref, {
count: ((docSnap.data() && docSnap.data().count) || 0) + 1
}));
// on delete
} else if (change.before.exists && !change.after.exists) {
return t
.get(firestore.collection('metadatas')
.doc(collectionName))
.then(docSnap =>
t.set(docSnap.ref, {
count: docSnap.data().count - 1
}));
}
return null;
});
Use cases here:
/**
* Count documents in articles collection.
*/
exports.articlesCounter = functions.firestore
.document('articles/{id}')
.onWrite(documentCounter('articles'));
/**
* Count documents in customers collection.
*/
exports.customersCounter = functions.firestore
.document('customers/{id}')
.onWrite(documentCounter('customers'));
As you can see, the key to prevent multiple execution is the property called eventId in the context object. If the function has been handled many times for the same event, the event id will be the same in all cases. Unfortunately, you must have "events" collection in your database.
In 2020 this is still not available in the Firebase SDK however it is available in Firebase Extensions (Beta) however it's pretty complex to setup and use...
A reasonable approach
Helpers... (create/delete seems redundant but is cheaper than onUpdate)
export const onCreateCounter = () => async (
change,
context
) => {
const collectionPath = change.ref.parent.path;
const statsDoc = db.doc("counters/" + collectionPath);
const countDoc = {};
countDoc["count"] = admin.firestore.FieldValue.increment(1);
await statsDoc.set(countDoc, { merge: true });
};
export const onDeleteCounter = () => async (
change,
context
) => {
const collectionPath = change.ref.parent.path;
const statsDoc = db.doc("counters/" + collectionPath);
const countDoc = {};
countDoc["count"] = admin.firestore.FieldValue.increment(-1);
await statsDoc.set(countDoc, { merge: true });
};
export interface CounterPath {
watch: string;
name: string;
}
Exported Firestore hooks
export const Counters: CounterPath[] = [
{
name: "count_buildings",
watch: "buildings/{id2}"
},
{
name: "count_buildings_subcollections",
watch: "buildings/{id2}/{id3}/{id4}"
}
];
Counters.forEach(item => {
exports[item.name + '_create'] = functions.firestore
.document(item.watch)
.onCreate(onCreateCounter());
exports[item.name + '_delete'] = functions.firestore
.document(item.watch)
.onDelete(onDeleteCounter());
});
In action
The building root collection and all sub collections will be tracked.
Here under the /counters/ root path
Now collection counts will update automatically and eventually! If you need a count, just use the collection path and prefix it with counters.
const collectionPath = 'buildings/138faicnjasjoa89/buildingContacts';
const collectionCount = await db
.doc('counters/' + collectionPath)
.get()
.then(snap => snap.get('count'));
Limitations
As this approach uses a single database and document, it is limited to the Firestore constraint of 1 Update per Second for each counter. It will be eventually consistent, but in cases where large amounts of documents are added/removed the counter will lag behind the actual collection count.
I agree with #Matthew, it will cost a lot if you perform such query.
[ADVICE FOR DEVELOPERS BEFORE STARTING THEIR PROJECTS]
Since we have foreseen this situation at the beginning, we can actually make a collection namely counters with a document to store all the counters in a field with type number.
For example:
For each CRUD operation on the collection, update the counter document:
When you create a new collection/subcollection: (+1 in the counter) [1 write operation]
When you delete a collection/subcollection: (-1 in the counter) [1 write operation]
When you update an existing collection/subcollection, do nothing on the counter document: (0)
When you read an existing collection/subcollection, do nothing on the counter document: (0)
Next time, when you want to get the number of collection, you just need to query/point to the document field. [1 read operation]
In addition, you can store the collections name in an array, but this will be tricky, the condition of array in firebase is shown as below:
// we send this
['a', 'b', 'c', 'd', 'e']
// Firebase stores this
{0: 'a', 1: 'b', 2: 'c', 3: 'd', 4: 'e'}
// since the keys are numeric and sequential,
// if we query the data, we get this
['a', 'b', 'c', 'd', 'e']
// however, if we then delete a, b, and d,
// they are no longer mostly sequential, so
// we do not get back an array
{2: 'c', 4: 'e'}
So, if you are not going to delete the collection , you can actually use array to store list of collections name instead of querying all the collection every time.
Hope it helps!
As of October 2022, Firestore has introduced a count() method on the client SDKs. Now you can count for a query without downloads.
For 1000 documents, it will charge you for 1 document read.
Web (v9)
Introduced in Firebase 9.11.0:
const collectionRef = collection(db, "cities");
const snapshot = await getCountFromServer(collectionRef);
console.log('count: ', snapshot.data().count);
Web V8
Not Available.
Node (Admin)
const collectionRef = db.collection('cities');
const snapshot = await collectionRef.count().get();
console.log(snapshot.data().count);
Android (Kotlin)
Introduced in firestore v24.4.0 (BoM 31.0.0):
val query = db.collection("cities")
val countQuery = query.count()
countQuery.get(AggregateSource.SERVER).addOnCompleteListener { task ->
if (task.isSuccessful) {
val snapshot = task.result
Log.d(TAG, "Count: ${snapshot.count}")
} else {
Log.d(TAG, "Count failed: ", task.getException())
}
}
Apple Platforms (Swift)
Introduced in Firestore v10.0.0:
do {
let query = db.collection("cities")
let countQuery = query.countAggregateQuery
let snapshot = try await countQuery.aggregation(source: AggregateSource.server)
print(snapshot.count)
} catch {
print(error)
}
Increment a counter using admin.firestore.FieldValue.increment:
exports.onInstanceCreate = functions.firestore.document('projects/{projectId}/instances/{instanceId}')
.onCreate((snap, context) =>
db.collection('projects').doc(context.params.projectId).update({
instanceCount: admin.firestore.FieldValue.increment(1),
})
);
exports.onInstanceDelete = functions.firestore.document('projects/{projectId}/instances/{instanceId}')
.onDelete((snap, context) =>
db.collection('projects').doc(context.params.projectId).update({
instanceCount: admin.firestore.FieldValue.increment(-1),
})
);
In this example we increment an instanceCount field in the project each time a document is added to the instances sub collection. If the field doesn't exist yet it will be created and incremented to 1.
The incrementation is transactional internally but you should use a distributed counter if you need to increment more frequently than every 1 second.
It's often preferable to implement onCreate and onDelete rather than onWrite as you will call onWrite for updates which means you are spending more money on unnecessary function invocations (if you update the docs in your collection).
No, there is no built-in support for aggregation queries right now. However there are a few things you could do.
The first is documented here. You can use transactions or cloud functions to maintain aggregate information:
This example shows how to use a function to keep track of the number of ratings in a subcollection, as well as the average rating.
exports.aggregateRatings = firestore
.document('restaurants/{restId}/ratings/{ratingId}')
.onWrite(event => {
// Get value of the newly added rating
var ratingVal = event.data.get('rating');
// Get a reference to the restaurant
var restRef = db.collection('restaurants').document(event.params.restId);
// Update aggregations in a transaction
return db.transaction(transaction => {
return transaction.get(restRef).then(restDoc => {
// Compute new number of ratings
var newNumRatings = restDoc.data('numRatings') + 1;
// Compute new average rating
var oldRatingTotal = restDoc.data('avgRating') * restDoc.data('numRatings');
var newAvgRating = (oldRatingTotal + ratingVal) / newNumRatings;
// Update restaurant info
return transaction.update(restRef, {
avgRating: newAvgRating,
numRatings: newNumRatings
});
});
});
});
The solution that jbb mentioned is also useful if you only want to count documents infrequently. Make sure to use the select() statement to avoid downloading all of each document (that's a lot of bandwidth when you only need a count). select() is only available in the server SDKs for now so that solution won't work in a mobile app.
UPDATE 11/20
I created an npm package for easy access to a counter function: https://code.build/p/9DicAmrnRoK4uk62Hw1bEV/firestore-counters
I created a universal function using all these ideas to handle all counter situations (except queries).
The only exception would be when doing so many writes a second, it
slows you down. An example would be likes on a trending post. It is
overkill on a blog post, for example, and will cost you more. I
suggest creating a separate function in that case using shards:
https://firebase.google.com/docs/firestore/solutions/counters
// trigger collections
exports.myFunction = functions.firestore
.document('{colId}/{docId}')
.onWrite(async (change: any, context: any) => {
return runCounter(change, context);
});
// trigger sub-collections
exports.mySubFunction = functions.firestore
.document('{colId}/{docId}/{subColId}/{subDocId}')
.onWrite(async (change: any, context: any) => {
return runCounter(change, context);
});
// add change the count
const runCounter = async function (change: any, context: any) {
const col = context.params.colId;
const eventsDoc = '_events';
const countersDoc = '_counters';
// ignore helper collections
if (col.startsWith('_')) {
return null;
}
// simplify event types
const createDoc = change.after.exists && !change.before.exists;
const updateDoc = change.before.exists && change.after.exists;
if (updateDoc) {
return null;
}
// check for sub collection
const isSubCol = context.params.subDocId;
const parentDoc = `${countersDoc}/${context.params.colId}`;
const countDoc = isSubCol
? `${parentDoc}/${context.params.docId}/${context.params.subColId}`
: `${parentDoc}`;
// collection references
const countRef = db.doc(countDoc);
const countSnap = await countRef.get();
// increment size if doc exists
if (countSnap.exists) {
// createDoc or deleteDoc
const n = createDoc ? 1 : -1;
const i = admin.firestore.FieldValue.increment(n);
// create event for accurate increment
const eventRef = db.doc(`${eventsDoc}/${context.eventId}`);
return db.runTransaction(async (t: any): Promise<any> => {
const eventSnap = await t.get(eventRef);
// do nothing if event exists
if (eventSnap.exists) {
return null;
}
// add event and update size
await t.update(countRef, { count: i });
return t.set(eventRef, {
completed: admin.firestore.FieldValue.serverTimestamp()
});
}).catch((e: any) => {
console.log(e);
});
// otherwise count all docs in the collection and add size
} else {
const colRef = db.collection(change.after.ref.parent.path);
return db.runTransaction(async (t: any): Promise<any> => {
// update size
const colSnap = await t.get(colRef);
return t.set(countRef, { count: colSnap.size });
}).catch((e: any) => {
console.log(e);
});;
}
}
This handles events, increments, and transactions. The beauty in this, is that if you are not sure about the accuracy of a document (probably while still in beta), you can delete the counter to have it automatically add them up on the next trigger. Yes, this costs, so don't delete it otherwise.
Same kind of thing to get the count:
const collectionPath = 'buildings/138faicnjasjoa89/buildingContacts';
const colSnap = await db.doc('_counters/' + collectionPath).get();
const count = colSnap.get('count');
Also, you may want to create a cron job (scheduled function) to remove old events to save money on database storage. You need at least a blaze plan, and there may be some more configuration. You could run it every sunday at 11pm, for example.
https://firebase.google.com/docs/functions/schedule-functions
This is untested, but should work with a few tweaks:
exports.scheduledFunctionCrontab = functions.pubsub.schedule('5 11 * * *')
.timeZone('America/New_York')
.onRun(async (context) => {
// get yesterday
const yesterday = new Date();
yesterday.setDate(yesterday.getDate() - 1);
const eventFilter = db.collection('_events').where('completed', '<=', yesterday);
const eventFilterSnap = await eventFilter.get();
eventFilterSnap.forEach(async (doc: any) => {
await doc.ref.delete();
});
return null;
});
And last, don't forget to protect the collections in firestore.rules:
match /_counters/{document} {
allow read;
allow write: if false;
}
match /_events/{document} {
allow read, write: if false;
}
Update: Queries
Adding to my other answer if you want to automate query counts as well, you can use this modified code in your cloud function:
if (col === 'posts') {
// counter reference - user doc ref
const userRef = after ? after.userDoc : before.userDoc;
// query reference
const postsQuery = db.collection('posts').where('userDoc', "==", userRef);
// add the count - postsCount on userDoc
await addCount(change, context, postsQuery, userRef, 'postsCount');
}
return delEvents();
Which will automatically update the postsCount in the userDocument. You could easily add other one to many counts this way. This just gives you ideas of how you can automate things. I also gave you another way to delete the events. You have to read each date to delete it, so it won't really save you to delete them later, just makes the function slower.
/**
* Adds a counter to a doc
* #param change - change ref
* #param context - context ref
* #param queryRef - the query ref to count
* #param countRef - the counter document ref
* #param countName - the name of the counter on the counter document
*/
const addCount = async function (change: any, context: any,
queryRef: any, countRef: any, countName: string) {
// events collection
const eventsDoc = '_events';
// simplify event type
const createDoc = change.after.exists && !change.before.exists;
// doc references
const countSnap = await countRef.get();
// increment size if field exists
if (countSnap.get(countName)) {
// createDoc or deleteDoc
const n = createDoc ? 1 : -1;
const i = admin.firestore.FieldValue.increment(n);
// create event for accurate increment
const eventRef = db.doc(`${eventsDoc}/${context.eventId}`);
return db.runTransaction(async (t: any): Promise<any> => {
const eventSnap = await t.get(eventRef);
// do nothing if event exists
if (eventSnap.exists) {
return null;
}
// add event and update size
await t.set(countRef, { [countName]: i }, { merge: true });
return t.set(eventRef, {
completed: admin.firestore.FieldValue.serverTimestamp()
});
}).catch((e: any) => {
console.log(e);
});
// otherwise count all docs in the collection and add size
} else {
return db.runTransaction(async (t: any): Promise<any> => {
// update size
const colSnap = await t.get(queryRef);
return t.set(countRef, { [countName]: colSnap.size }, { merge: true });
}).catch((e: any) => {
console.log(e);
});;
}
}
/**
* Deletes events over a day old
*/
const delEvents = async function () {
// get yesterday
const yesterday = new Date();
yesterday.setDate(yesterday.getDate() - 1);
const eventFilter = db.collection('_events').where('completed', '<=', yesterday);
const eventFilterSnap = await eventFilter.get();
eventFilterSnap.forEach(async (doc: any) => {
await doc.ref.delete();
});
return null;
}
I should also warn you that universal functions will run on every
onWrite call period. It may be cheaper to only run the function on
onCreate and on onDelete instances of your specific collections. Like
the noSQL database we are using, repeated code and data can save you
money.
There is no direct option available. You cant't do db.collection("CollectionName").count().
Below are the two ways by which you can find the count of number of documents within a collection.
1 :- Get all the documents in the collection and then get it's size.(Not the best Solution)
db.collection("CollectionName").get().subscribe(doc=>{
console.log(doc.size)
})
By using above code your document reads will be equal to the size of documents within a collection and that is the reason why one must avoid using above solution.
2:- Create a separate document with in your collection which will store the count of number of documents in the collection.(Best Solution)
db.collection("CollectionName").doc("counts")get().subscribe(doc=>{
console.log(doc.count)
})
Above we created a document with name counts to store all the count information.You can update the count document in the following way:-
Create a firestore triggers on the document counts
Increment the count property of counts document when a new document is created.
Decrement the count property of counts document when a document is deleted.
w.r.t price (Document Read = 1) and fast data retrieval the above solution is good.
A workaround is to:
write a counter in a firebase doc, which you increment within a transaction everytime you create a new entry
You store the count in a field of your new entry (i.e: position: 4).
Then you create an index on that field (position DESC).
You can do a skip+limit with a query.Where("position", "<" x).OrderBy("position", DESC)
Hope this helps!
I have try a lot with different approaches.
And finally, I improve one of the methods.
First you need to create a separate collection and save there all events.
Second you need to create a new lambda to be triggered by time. This lambda will Count events in event collection and clear event documents.
Code details in article.
https://medium.com/#ihor.malaniuk/how-to-count-documents-in-google-cloud-firestore-b0e65863aeca
one of the fast + money saver trick is that:-
make a doc and store a 'count' variable in firestore, when user add new doc in the collection, increase that variable, and when user delete a doc, decrease variable. e.g.
updateDoc(doc(db, "Count_collection", "Count_Doc"), {count: increment(1)});
note: use (-1) for decreasing, (1) for increasing count
How it save money and time:-
you(firebase) don't need to loop through the collection, nor browser needs to load whole collection to count number of docs.
all the counts are save in a doc of only one variable named "count" or whatever, so less than 1kb data is used, and it use only 1 reads in firebase firestore.
Solution using pagination with offset & limit:
public int collectionCount(String collection) {
Integer page = 0;
List<QueryDocumentSnapshot> snaps = new ArrayList<>();
findDocsByPage(collection, page, snaps);
return snaps.size();
}
public void findDocsByPage(String collection, Integer page,
List<QueryDocumentSnapshot> snaps) {
try {
Integer limit = 26000;
FieldPath[] selectedFields = new FieldPath[] { FieldPath.of("id") };
List<QueryDocumentSnapshot> snapshotPage;
snapshotPage = fireStore()
.collection(collection)
.select(selectedFields)
.offset(page * limit)
.limit(limit)
.get().get().getDocuments();
if (snapshotPage.size() > 0) {
snaps.addAll(snapshotPage);
page++;
findDocsByPage(collection, page, snaps);
}
} catch (InterruptedException | ExecutionException e) {
e.printStackTrace();
}
}
findDocsPage it's a recursive method to find all pages of collection
selectedFields for otimize query and get only id field instead full body of document
limit max size of each query page
page define inicial page for pagination
From the tests I did it worked well for collections with up to approximately 120k records!
Firestore is introducing a new Query.count() that fetches the count of a query without fetching the docs.
This would allow to simply query all collection items and get the count of that query.
Ref:
Firebase 10 iOS SDK
[JS SDK PR] (https://github.com/firebase/firebase-js-sdk/pull/6608)
There's a new build in function since version 9.11.0 called getCountFromServer(), which fetches the number of documents in the result set without actually downloading the documents.
https://firebase.google.com/docs/reference/js/firestore_#getcountfromserver
Took me a while to get this working based on some of the answers above, so I thought I'd share it for others to use. I hope it's useful.
'use strict';
const functions = require('firebase-functions');
const admin = require('firebase-admin');
admin.initializeApp();
const db = admin.firestore();
exports.countDocumentsChange = functions.firestore.document('library/{categoryId}/documents/{documentId}').onWrite((change, context) => {
const categoryId = context.params.categoryId;
const categoryRef = db.collection('library').doc(categoryId)
let FieldValue = require('firebase-admin').firestore.FieldValue;
if (!change.before.exists) {
// new document created : add one to count
categoryRef.update({numberOfDocs: FieldValue.increment(1)});
console.log("%s numberOfDocs incremented by 1", categoryId);
} else if (change.before.exists && change.after.exists) {
// updating existing document : Do nothing
} else if (!change.after.exists) {
// deleting document : subtract one from count
categoryRef.update({numberOfDocs: FieldValue.increment(-1)});
console.log("%s numberOfDocs decremented by 1", categoryId);
}
return 0;
});
This uses counting to create numeric unique ID. In my use, I will not be decrementing ever, even when the document that the ID is needed for is deleted.
Upon a collection creation that needs unique numeric value
Designate a collection appData with one document, set with .doc id only
Set uniqueNumericIDAmount to 0 in the firebase firestore console
Use doc.data().uniqueNumericIDAmount + 1 as the unique numeric id
Update appData collection uniqueNumericIDAmount with firebase.firestore.FieldValue.increment(1)
firebase
.firestore()
.collection("appData")
.doc("only")
.get()
.then(doc => {
var foo = doc.data();
foo.id = doc.id;
// your collection that needs a unique ID
firebase
.firestore()
.collection("uniqueNumericIDs")
.doc(user.uid)// user id in my case
.set({// I use this in login, so this document doesn't
// exist yet, otherwise use update instead of set
phone: this.state.phone,// whatever else you need
uniqueNumericID: foo.uniqueNumericIDAmount + 1
})
.then(() => {
// upon success of new ID, increment uniqueNumericIDAmount
firebase
.firestore()
.collection("appData")
.doc("only")
.update({
uniqueNumericIDAmount: firebase.firestore.FieldValue.increment(
1
)
})
.catch(err => {
console.log(err);
});
})
.catch(err => {
console.log(err);
});
});
var variable=0
variable=variable+querySnapshot.count
then if you are to use it on a String variable then
let stringVariable= String(variable)
Along with my npm package adv-firestore-functions above, you can also just use firestore rules to force a good counter:
Firestore Rules
function counter() {
let docPath = /databases/$(database)/documents/_counters/$(request.path[3]);
let afterCount = getAfter(docPath).data.count;
let beforeCount = get(docPath).data.count;
let addCount = afterCount == beforeCount + 1;
let subCount = afterCount == beforeCount - 1;
let newId = getAfter(docPath).data.docId == request.path[4];
let deleteDoc = request.method == 'delete';
let createDoc = request.method == 'create';
return (newId && subCount && deleteDoc) || (newId && addCount && createDoc);
}
function counterDoc() {
let doc = request.path[4];
let docId = request.resource.data.docId;
let afterCount = request.resource.data.count;
let beforeCount = resource.data.count;
let docPath = /databases/$(database)/documents/$(doc)/$(docId);
let createIdDoc = existsAfter(docPath) && !exists(docPath);
let deleteIdDoc = !existsAfter(docPath) && exists(docPath);
let addCount = afterCount == beforeCount + 1;
let subCount = afterCount == beforeCount - 1;
return (createIdDoc && addCount) || (deleteIdDoc && subCount);
}
and use them like so:
match /posts/{document} {
allow read;
allow update;
allow create: if counter();
allow delete: if counter();
}
match /_counters/{document} {
allow read;
allow write: if counterDoc();
}
Frontend
Replace your set and delete functions with these:
set
async setDocWithCounter(
ref: DocumentReference<DocumentData>,
data: {
[x: string]: any;
},
options: SetOptions): Promise<void> {
// counter collection
const counterCol = '_counters';
const col = ref.path.split('/').slice(0, -1).join('/');
const countRef = doc(this.afs, counterCol, col);
const countSnap = await getDoc(countRef);
const refSnap = await getDoc(ref);
// don't increase count if edit
if (refSnap.exists()) {
await setDoc(ref, data, options);
// increase count
} else {
const batch = writeBatch(this.afs);
batch.set(ref, data, options);
// if count exists
if (countSnap.exists()) {
batch.update(countRef, {
count: increment(1),
docId: ref.id
});
// create count
} else {
// will only run once, should not use
// for mature apps
const colRef = collection(this.afs, col);
const colSnap = await getDocs(colRef);
batch.set(countRef, {
count: colSnap.size + 1,
docId: ref.id
});
}
batch.commit();
}
}
delete
async delWithCounter(
ref: DocumentReference<DocumentData>
): Promise<void> {
// counter collection
const counterCol = '_counters';
const col = ref.path.split('/').slice(0, -1).join('/');
const countRef = doc(this.afs, counterCol, col);
const countSnap = await getDoc(countRef);
const batch = writeBatch(this.afs);
// if count exists
batch.delete(ref);
if (countSnap.exists()) {
batch.update(countRef, {
count: increment(-1),
docId: ref.id
});
}
/*
if ((countSnap.data() as any).count == 1) {
batch.delete(countRef);
}*/
batch.commit();
}
see here for more info...
J
This feature is now supported in FireStore, albeit in Beta.
Here are the official Firebase docs
With the new version of Firebase, you can now run aggregated queries!
Simply write
.count().get();
after your query.
As it stands, firebase only allows server-side count, like this
const collectionRef = db.collection('cities');
const snapshot = await collectionRef.count().get();
console.log(snapshot.data().count);
Please not this is for nodeJS
New feature available in Firebase/Firestore provides a count of documents in a collection:
See this thread to see how to achieve it, with an example.
How To Count Number of Documents in a Collection in Firebase Firestore With a WHERE query in react.js
According to this documentation Cloud Firestore supports the count() aggregation query and is available in preview.
The Flutter/Dart code was missing (at the time of writing this) so I played around with it and the following function seems to work:
Future<int> getCount(String path) async {
var collection = _fireStore.collection(path);
var countQuery = collection.count();
var snapShot = await countQuery.get(source: AggregateSource.server);
return snapShot.count;
}
firebaseFirestore.collection("...").addSnapshotListener(new EventListener<QuerySnapshot>() {
#Override
public void onEvent(QuerySnapshot documentSnapshots, FirebaseFirestoreException e) {
int Counter = documentSnapshots.size();
}
});
So my solution for this problem is a bit non-technical, not super precise, but good enough for me.
Those are my documents. As I have a lot of them (100k+) there are 'laws of big numbers' happening. I can assume that there is less-or-more equal number of items having id starting with 0, 1, 2, etc.
So what I do is I scroll my list till I get into id's starting with 1, or with 01, depending on how long you have to scroll
👆 here we are.
Now, having scrolled so far, I open the inspector and see how much did I scroll and divide it by height of single element
Had to scroll 82000px to get items with id starting with 1. Height of single element is 32px.
It means I have 2500 with id starting with 0, so now I multiply it by number of possible 'starting char'. In firebase it can be A-Z, a-z, 0-9 which means it's 24 + 24 + 10 = 58.
It means I have ~~2500*58 so it gives roughly 145000 items in my collection.
Summarizing: What is wrong with you firebase?
Let's say I have some bookschema, and I want to get books in a random order whenever the page loads. I cannot shuffle the find result like this:
const books = await BookModel.find({}, (err, res) => { // eslint-disable-line
// console.log(res);
if (err) {
console.log(err);
}
}).limit(args.limit || 3).skip(args.offset || 3).lean();
return _.shuffle(books);
Reason being that on each additional skip/limit, e. g. when the user scrolls down to load more results, the randomization would start again from scratch and the frontend results would shuffle around.
What I want is that it loads the first e. g. 9 results in randomized order, then loads another 9 in randomized order. Is there any way to do this with Mongoose out of the box?
I think we can solve this the following way:
=> we need to send the already read ids to the server for the next chunk
...
let ids = [];
if (retrievedIds.length) {
ids = retrievedIds.map((id) => mongoose.Types.ObjectId(id));
}
let filter = { _id: { $nin: ids} }
db.users.aggregate([
{ $match: filter }, //
{ $sample: { size: 10 } }
])
I have a Meteor-react app, what contains a collection, with a lots of data. I am displaying the data with pagination.
At the server side I am just publishing the data for the current page.
So, I am publishing some data at the server side:
Meteor.publish('animals', function(currPage,displayPerPage, options) {
const userId = this.userId;
if (userId) {
const currentUser = Meteor.users.findOne({ _id: userId });
let skip = (currPage - 1) * displayPerPage;
if (displayPerPage > 0) {
Counts.publish(this, 'count-animals', Animals.find(
{$and: [
// Counter Query
}
), {fastCount: true});
return Animals.find(
{$and: [
// Data query
]}, {sort: options.sortOption, skip: skip, limit: displayPerPage });
} else {
Counts.publish(this, 'count-animals', 0);
return [];
}
}
});
And on the client side I am using tracker:
export default AnimalsContainer = withTracker(({subscriptionName, subscriptionFun, options, counterName}) => {
let displayPerPage = Session.get("displayPerPage");
let currPage = Session.get("currPage");
let paginationSub = Meteor.subscribe(subscriptionName, currPage, displayPerPage, options );
let countAnimals = Counts.get(counterName);
let data = Animals.find({}).fetch({});
// console.log(data);
return {
// data: data,
data: data.length <= displayPerPage ? data : data.slice(0, displayPerPage),
countAnimals: countAnimals,
}
})(Animals);
The problem is:
When I try to modify the sort options on the client side, the server sort not from the first data(Skippind the first some). Sometimes from the 20 th sometimes from the 10 th.
The type checks are done at both side.
Two things I can think of.
Keep on eye on the {sort: options.sortOption, skip: skip, limit: displayPerPage } order. As far as I know, it runs in the order you place it. So it sorts first, then skips, then limits.
Do sorts on both client and server. When the sort happens on the server and it's streamed to the client, the client holds a mini mongo version which doesn't guarantee an order. Therefore you need to sort the client as well.
I'm trying to return create a paginated list. I used graphql to query the data. With my query, I pass the number of records I need (In a variable named first) and the ID of the last fetched record (In a varible called after). Now I managed to write a query (Note that I used mongoose) to fetch the records. Now what I need to do is get the relavant information to perform the pagination like hasNextPage, hasPreviousPage, currentPage and totalPages.
To get most of these information I need to get the total number of records in the database. To do that I need to send another db request.
I also need to know the position of the record in the table. No idea how.
Here's the query:
new Promise((resolve, reject) =>
Company.where('_id')
.gt(after)
.limit(first)
.lean()
.exec((error, doc) => {
if (error) {
reject(error);
}
resolve({
edges: doc,
pageInfo: {
hasNextPage: '...',
hasPreviousPage: '...',
currentPage: '...',
totalPages: '...'
}
});
}))
Any idea how to do this efficiently?
you can try this module mongoose-paginate
here what i uses, for pagination,
var current = req.query.filter.current;
var limit = req.query.filter.limit;
console.log('params.query.filter.current',current);
var skip = Number(limit)*Number(current)-Number(limit);
console.log('skip::',skip);
Cours.find({'attributes.version.status': true}).skip(skip).limit(limit).sort({_id:'asc'}).exec(function (err, resulta) {
if (err) {
console.log('erreur trouverCours');
res.json({
protecteds: err
});
}
console.log('cours ::', resulta);
res.json({
"data": resulta
});
});
I am writing a webapp with Node.js and mongoose. How can I paginate the results I get from a .find() call? I would like a functionality comparable to "LIMIT 50,100" in SQL.
I'm am very disappointed by the accepted answers in this question. This will not scale. If you read the fine print on cursor.skip( ):
The cursor.skip() method is often expensive because it requires the server to walk from the beginning of the collection or index to get the offset or skip position before beginning to return result. As offset (e.g. pageNumber above) increases, cursor.skip() will become slower and more CPU intensive. With larger collections, cursor.skip() may become IO bound.
To achieve pagination in a scaleable way combine a limit( ) along with at least one filter criterion, a createdOn date suits many purposes.
MyModel.find( { createdOn: { $lte: request.createdOnBefore } } )
.limit( 10 )
.sort( '-createdOn' )
After taking a closer look at the Mongoose API with the information provided by Rodolphe, I figured out this solution:
MyModel.find(query, fields, { skip: 10, limit: 5 }, function(err, results) { ... });
Pagination using mongoose, express and jade - Here's a link to my blog with more detail
var perPage = 10
, page = Math.max(0, req.params.page)
Event.find()
.select('name')
.limit(perPage)
.skip(perPage * page)
.sort({
name: 'asc'
})
.exec(function(err, events) {
Event.count().exec(function(err, count) {
res.render('events', {
events: events,
page: page,
pages: count / perPage
})
})
})
You can chain just like that:
var query = Model.find().sort('mykey', 1).skip(2).limit(5)
Execute the query using exec
query.exec(callback);
In this case, you can add the query page and/ or limit to your URL as a query string.
For example:
?page=0&limit=25 // this would be added onto your URL: http:localhost:5000?page=0&limit=25
Since it would be a String we need to convert it to a Number for our calculations. Let's do it using the parseInt method and let's also provide some default values.
const pageOptions = {
page: parseInt(req.query.page, 10) || 0,
limit: parseInt(req.query.limit, 10) || 10
}
sexyModel.find()
.skip(pageOptions.page * pageOptions.limit)
.limit(pageOptions.limit)
.exec(function (err, doc) {
if(err) { res.status(500).json(err); return; };
res.status(200).json(doc);
});
BTW
Pagination starts with 0
You can use a little package called Mongoose Paginate that makes it easier.
$ npm install mongoose-paginate
After in your routes or controller, just add :
/**
* querying for `all` {} items in `MyModel`
* paginating by second page, 10 items per page (10 results, page 2)
**/
MyModel.paginate({}, 2, 10, function(error, pageCount, paginatedResults) {
if (error) {
console.error(error);
} else {
console.log('Pages:', pageCount);
console.log(paginatedResults);
}
}
Query:
search = productName
Params:
page = 1
// Pagination
router.get("/search/:page", (req, res, next) => {
const resultsPerPage = 5;
let page = req.params.page >= 1 ? req.params.page : 1;
const query = req.query.search;
page = page - 1
Product.find({ name: query })
.select("name")
.sort({ name: "asc" })
.limit(resultsPerPage)
.skip(resultsPerPage * page)
.then((results) => {
return res.status(200).send(results);
})
.catch((err) => {
return res.status(500).send(err);
});
});
This is a example you can try this,
var _pageNumber = 2,
_pageSize = 50;
Student.count({},function(err,count){
Student.find({}, null, {
sort: {
Name: 1
}
}).skip(_pageNumber > 0 ? ((_pageNumber - 1) * _pageSize) : 0).limit(_pageSize).exec(function(err, docs) {
if (err)
res.json(err);
else
res.json({
"TotalCount": count,
"_Array": docs
});
});
});
Try using mongoose function for pagination. Limit is the number of records per page and number of the page.
var limit = parseInt(body.limit);
var skip = (parseInt(body.page)-1) * parseInt(limit);
db.Rankings.find({})
.sort('-id')
.limit(limit)
.skip(skip)
.exec(function(err,wins){
});
This is what I done it on code
var paginate = 20;
var page = pageNumber;
MySchema.find({}).sort('mykey', 1).skip((pageNumber-1)*paginate).limit(paginate)
.exec(function(err, result) {
// Write some stuff here
});
That is how I done it.
Simple and powerful pagination solution
async getNextDocs(no_of_docs_required: number = 5, last_doc_id?: string) {
let docs
if (!last_doc_id) {
// get first 5 docs
docs = await MySchema.find().sort({ _id: -1 }).limit(no_of_docs_required)
}
else {
// get next 5 docs according to that last document id
docs = await MySchema.find({_id: {$lt: last_doc_id}})
.sort({ _id: -1 }).limit(no_of_docs_required)
}
return docs
}
last_doc_id: the last document id that you get
no_of_docs_required: the number of docs that you want to fetch i.e. 5, 10, 50 etc.
If you don't provide the last_doc_id to the method, you'll get i.e. 5 latest docs
If you've provided the last_doc_id then you'll get the next i.e. 5 documents.
There are some good answers giving the solution that uses skip() & limit(), however, in some scenarios, we also need documents count to generate pagination. Here's what we do in our projects:
const PaginatePlugin = (schema, options) => {
options = options || {}
schema.query.paginate = async function(params) {
const pagination = {
limit: options.limit || 10,
page: 1,
count: 0
}
pagination.limit = parseInt(params.limit) || pagination.limit
const page = parseInt(params.page)
pagination.page = page > 0 ? page : pagination.page
const offset = (pagination.page - 1) * pagination.limit
const [data, count] = await Promise.all([
this.limit(pagination.limit).skip(offset),
this.model.countDocuments(this.getQuery())
]);
pagination.count = count;
return { data, pagination }
}
}
mySchema.plugin(PaginatePlugin, { limit: DEFAULT_LIMIT })
// using async/await
const { data, pagination } = await MyModel.find(...)
.populate(...)
.sort(...)
.paginate({ page: 1, limit: 10 })
// or using Promise
MyModel.find(...).paginate(req.query)
.then(({ data, pagination }) => {
})
.catch(err => {
})
Here is a version that I attach to all my models. It depends on underscore for convenience and async for performance. The opts allows for field selection and sorting using the mongoose syntax.
var _ = require('underscore');
var async = require('async');
function findPaginated(filter, opts, cb) {
var defaults = {skip : 0, limit : 10};
opts = _.extend({}, defaults, opts);
filter = _.extend({}, filter);
var cntQry = this.find(filter);
var qry = this.find(filter);
if (opts.sort) {
qry = qry.sort(opts.sort);
}
if (opts.fields) {
qry = qry.select(opts.fields);
}
qry = qry.limit(opts.limit).skip(opts.skip);
async.parallel(
[
function (cb) {
cntQry.count(cb);
},
function (cb) {
qry.exec(cb);
}
],
function (err, results) {
if (err) return cb(err);
var count = 0, ret = [];
_.each(results, function (r) {
if (typeof(r) == 'number') {
count = r;
} else if (typeof(r) != 'number') {
ret = r;
}
});
cb(null, {totalCount : count, results : ret});
}
);
return qry;
}
Attach it to your model schema.
MySchema.statics.findPaginated = findPaginated;
Above answer's holds good.
Just an add-on for anyone who is into async-await rather than
promise !!
const findAllFoo = async (req, resp, next) => {
const pageSize = 10;
const currentPage = 1;
try {
const foos = await FooModel.find() // find all documents
.skip(pageSize * (currentPage - 1)) // we will not retrieve all records, but will skip first 'n' records
.limit(pageSize); // will limit/restrict the number of records to display
const numberOfFoos = await FooModel.countDocuments(); // count the number of records for that model
resp.setHeader('max-records', numberOfFoos);
resp.status(200).json(foos);
} catch (err) {
resp.status(500).json({
message: err
});
}
};
you can use the following line of code as well
per_page = parseInt(req.query.per_page) || 10
page_no = parseInt(req.query.page_no) || 1
var pagination = {
limit: per_page ,
skip:per_page * (page_no - 1)
}
users = await User.find({<CONDITION>}).limit(pagination.limit).skip(pagination.skip).exec()
this code will work in latest version of mongo
A solid approach to implement this would be to pass the values from the frontend using a query string. Let's say we want to get page #2 and also limit the output to 25 results.
The query string would look like this: ?page=2&limit=25 // this would be added onto your URL: http:localhost:5000?page=2&limit=25
Let's see the code:
// We would receive the values with req.query.<<valueName>> => e.g. req.query.page
// Since it would be a String we need to convert it to a Number in order to do our
// necessary calculations. Let's do it using the parseInt() method and let's also provide some default values:
const page = parseInt(req.query.page, 10) || 1; // getting the 'page' value
const limit = parseInt(req.query.limit, 10) || 25; // getting the 'limit' value
const startIndex = (page - 1) * limit; // this is how we would calculate the start index aka the SKIP value
const endIndex = page * limit; // this is how we would calculate the end index
// We also need the 'total' and we can get it easily using the Mongoose built-in **countDocuments** method
const total = await <<modelName>>.countDocuments();
// skip() will return a certain number of results after a certain number of documents.
// limit() is used to specify the maximum number of results to be returned.
// Let's assume that both are set (if that's not the case, the default value will be used for)
query = query.skip(startIndex).limit(limit);
// Executing the query
const results = await query;
// Pagination result
// Let's now prepare an object for the frontend
const pagination = {};
// If the endIndex is smaller than the total number of documents, we have a next page
if (endIndex < total) {
pagination.next = {
page: page + 1,
limit
};
}
// If the startIndex is greater than 0, we have a previous page
if (startIndex > 0) {
pagination.prev = {
page: page - 1,
limit
};
}
// Implementing some final touches and making a successful response (Express.js)
const advancedResults = {
success: true,
count: results.length,
pagination,
data: results
}
// That's it. All we have to do now is send the `results` to the frontend.
res.status(200).json(advancedResults);
I would suggest implementing this logic into middleware so you can be able to use it for various routes/ controllers.
You can do using mongoose-paginate-v2. For more info click here
const mongoose = require('mongoose');
const mongoosePaginate = require('mongoose-paginate-v2');
const mySchema = new mongoose.Schema({
// your schema code
});
mySchema.plugin(mongoosePaginate);
const myModel = mongoose.model('SampleModel', mySchema);
myModel.paginate().then({}) // Usage
I have found a very efficient way and implemented it myself, I think this way is the best for the following reasons:
It does not use skip, which time complexity doesn't scale well;
It uses IDs to query the document. Ids are indexed by default in MongoDB, making them very fast to query;
It uses lean queries, these are known to be VERY performative, as they remove a lot of "magic" from Mongoose and returns a document that comes kind of "raw" from MongoDB;
It doesn't depend on any third party packages that might contain vulnerabilities or have vulnerable dependencies.
The only caveat to this is that some methods of Mongoose, such as .save() will not work well with lean queries, such methods are listed in this awesome blog post, I really recommend this series, because it considers a lot of aspects, such as type security (which prevents critical errors) and PUT/ PATCH.
I will provide some context, this is a Pokémon repository, the pagination works as the following: The API receives unsafeId from the req.body object of Express, we need to convert this to string in order to prevent NoSQL injections (it could be an object with evil filters), this unsafeId can be an empty string or the ID of the last item of the previous page, it goes like this:
/**
* #description GET All with pagination, will return 200 in success
* and receives the last ID of the previous page or undefined for the first page
* Note: You should take care, read and consider about Off-By-One error
* #param {string|undefined|unknown} unsafeId - An entire page that comes after this ID will be returned
*/
async readPages(unsafeId) {
try {
const id = String(unsafeId || '');
let criteria;
if (id) {
criteria = {_id: {$gt: id}};
} // else criteria is undefined
// This query looks a bit redundant on `lean`, I just really wanted to make sure it is lean
const pokemon = await PokemonSchema.find(
criteria || {},
).setOptions({lean: true}).limit(15).lean();
// This would throw on an empty page
// if (pokemon.length < 1) {
// throw new PokemonNotFound();
// }
return pokemon;
} catch (error) {
// In this implementation, any error that is not defined by us
// will not return on the API to prevent information disclosure.
// our errors have this property, that indicate
// that no sensitive information is contained within this object
if (error.returnErrorResponse) {
throw error;
} // else
console.error(error.message);
throw new InternalServerError();
}
}
Now, to consume this and avoid Off-By-One errors in the frontend, you do it like the following, considering that pokemons is the Array of Pokémons documents that are returned from the API:
// Page zero
const pokemons = await fetchWithPagination({'page': undefined});
// Page one
// You can also use a fixed number of pages instead of `pokemons.length`
// But `pokemon.length` is more reliable (and a bit slower)
// You will have trouble with the last page if you use it with a constant
// predefined number
const id = pokemons[pokemons.length - 1]._id;
if (!id) {
throw new Error('Last element from page zero has no ID');
} // else
const page2 = await fetchWithPagination({'page': id});
As a note here, Mongoose IDs are always sequential, this means that any newer ID will always be greater than the older one, that is the foundation of this answer.
This approach has been tested agaisnt Off-By-One errors, for instance, the last element of a page could be returned as the first element of the following one (duplicated), or an element that is between the last of the previous page and the first of the current page might disappear.
When you are done with all the pages and request a page after the last element (one that does not exist), the response will be an empty array with 200 (OK), which is awesome!
The easiest and more speedy way is, paginate with the objectId
Example;
Initial load condition
condition = {limit:12, type:""};
Take the first and last ObjectId from response data
Page next condition
condition = {limit:12, type:"next", firstId:"57762a4c875adce3c38c662d", lastId:"57762a4c875adce3c38c6615"};
Page next condition
condition = {limit:12, type:"next", firstId:"57762a4c875adce3c38c6645", lastId:"57762a4c875adce3c38c6675"};
In mongoose
var condition = {};
var sort = { _id: 1 };
if (req.body.type == "next") {
condition._id = { $gt: req.body.lastId };
} else if (req.body.type == "prev") {
sort = { _id: -1 };
condition._id = { $lt: req.body.firstId };
}
var query = Model.find(condition, {}, { sort: sort }).limit(req.body.limit);
query.exec(function(err, properties) {
return res.json({ "result": result);
});
The best approach (IMO) is to use skip and limit BUT within a limited collections or documents.
To make the query within limited documents, we can use specific index like index on a DATE type field. See that below
let page = ctx.request.body.page || 1
let size = ctx.request.body.size || 10
let DATE_FROM = ctx.request.body.date_from
let DATE_TO = ctx.request.body.date_to
var start = (parseInt(page) - 1) * parseInt(size)
let result = await Model.find({ created_at: { $lte: DATE_FROM, $gte: DATE_TO } })
.sort({ _id: -1 })
.select('<fields>')
.skip( start )
.limit( size )
.exec(callback)
Most easiest plugin for pagination.
https://www.npmjs.com/package/mongoose-paginate-v2
Add plugin to a schema and then use model paginate method:
var mongoose = require('mongoose');
var mongoosePaginate = require('mongoose-paginate-v2');
var mySchema = new mongoose.Schema({
/* your schema definition */
});
mySchema.plugin(mongoosePaginate);
var myModel = mongoose.model('SampleModel', mySchema);
myModel.paginate().then({}) // Usage
let page,limit,skip,lastPage, query;
page = req.params.page *1 || 1; //This is the page,fetch from the server
limit = req.params.limit * 1 || 1; // This is the limit ,it also fetch from the server
skip = (page - 1) * limit; // Number of skip document
lastPage = page * limit; //last index
counts = await userModel.countDocuments() //Number of document in the collection
query = query.skip(skip).limit(limit) //current page
const paginate = {}
//For previous page
if(skip > 0) {
paginate.prev = {
page: page - 1,
limit: limit
}
//For next page
if(lastPage < counts) {
paginate.next = {
page: page + 1,
limit: limit
}
results = await query //Here is the final results of the query.
const page = req.query.page * 1 || 1;
const limit = req.query.limit * 1 || 1000;
const skip = (page - 1) * limit;
query = query.skip(skip).limit(limit);
This is example function for getting the result of skills model with pagination and limit options
export function get_skills(req, res){
console.log('get_skills');
var page = req.body.page; // 1 or 2
var size = req.body.size; // 5 or 10 per page
var query = {};
if(page < 0 || page === 0)
{
result = {'status': 401,'message':'invalid page number,should start with 1'};
return res.json(result);
}
query.skip = size * (page - 1)
query.limit = size
Skills.count({},function(err1,tot_count){ //to get the total count of skills
if(err1)
{
res.json({
status: 401,
message:'something went wrong!',
err: err,
})
}
else
{
Skills.find({},{},query).sort({'name':1}).exec(function(err,skill_doc){
if(!err)
{
res.json({
status: 200,
message:'Skills list',
data: data,
tot_count: tot_count,
})
}
else
{
res.json({
status: 401,
message: 'something went wrong',
err: err
})
}
}) //Skills.find end
}
});//Skills.count end
}
Using ts-mongoose-pagination
const trainers = await Trainer.paginate(
{ user: req.userId },
{
perPage: 3,
page: 1,
select: '-password, -createdAt -updatedAt -__v',
sort: { createdAt: -1 },
}
)
return res.status(200).json(trainers)
Below Code Is Working Fine For Me.
You can add finding filters also and user same in countDocs query to get accurate results.
export const yourController = async (req, res) => {
const { body } = req;
var perPage = body.limit,
var page = Math.max(0, body.page);
yourModel
.find() // You Can Add Your Filters inside
.limit(perPage)
.skip(perPage * (page - 1))
.exec(function (err, dbRes) {
yourModel.count().exec(function (err, count) { // You Can Add Your Filters inside
res.send(
JSON.stringify({
Articles: dbRes,
page: page,
pages: count / perPage,
})
);
});
});
};
You can write query like this.
mySchema.find().skip((page-1)*per_page).limit(per_page).exec(function(err, articles) {
if (err) {
return res.status(400).send({
message: err
});
} else {
res.json(articles);
}
});
page : page number coming from client as request parameters.
per_page : no of results shown per page
If you are using MEAN stack following blog post provides much of the information to create pagination in front end using angular-UI bootstrap and using mongoose skip and limit methods in the backend.
see : https://techpituwa.wordpress.com/2015/06/06/mean-js-pagination-with-angular-ui-bootstrap/
You can either use skip() and limit(), but it's very inefficient. A better solution would be a sort on indexed field plus limit().
We at Wunderflats have published a small lib here: https://github.com/wunderflats/goosepage
It uses the first way.
If you are using mongoose as a source for a restful api have a look at
'restify-mongoose' and its queries. It has exactly this functionality built in.
Any query on a collection provides headers that are helpful here
test-01:~$ curl -s -D - localhost:3330/data?sort=-created -o /dev/null
HTTP/1.1 200 OK
link: </data?sort=-created&p=0>; rel="first", </data?sort=-created&p=1>; rel="next", </data?sort=-created&p=134715>; rel="last"
.....
Response-Time: 37
So basically you get a generic server with a relatively linear load time for queries to collections. That is awesome and something to look at if you want to go into a own implementation.
app.get("/:page",(req,res)=>{
post.find({}).then((data)=>{
let per_page = 5;
let num_page = Number(req.params.page);
let max_pages = Math.ceil(data.length/per_page);
if(num_page == 0 || num_page > max_pages){
res.render('404');
}else{
let starting = per_page*(num_page-1)
let ending = per_page+starting
res.render('posts', {posts:data.slice(starting,ending), pages: max_pages, current_page: num_page});
}
});
});