CODEWITHSUNDEEP
firebaseflutterdartgoogle-cloud-firestorepagination
userh309
userh309

Reputation: 13

How do I know if there are more documents left to get from a firestore collection?

I'm using flutter and firebase. I use pagination, max 5 documents per page. How do I know if there are more documents left to get from a firestore collection. I want to use this information to enable/disable a next page button presented to the user.

limit: 5 (5 documents each time)

orderBy: "date" (newest first)

startAfterDocument: latestDocument (just a variable that holds the latest document)

This is how I fetch the documents.

collection.limit(5).orderBy("date", descending: true).startAfterDocument(latestDocument).get()

I thought about checking if the number of docs received from firestore is equal to 5, then assume there are more docs to get. But this will not work if I there are a total of n * 5 docs in the collection.

I thought about getting the last document in the collection and store this and compare this to every doc in the batches I get, if there is a match then I know I've reach the end, but this means one excess read.

Or maybe I could keep on getting docs until I get an empty list and assume I've reached the end of the collection.

I still feel there are a much better solution to this.

Let me know if you need more info, this is my first question on this account.

Upvotes: 1

Views: 758

Answers (2)

Ateeb Asif
Ateeb Asif

Reputation: 184

here's a way to get a large data from firebase collection

let latestDoc = null; // this is to store the last doc from a query 
 //result
const dataArr = []; // this is to store the data getting from firestore
let loadMore = true;  // this is to check if there's more data or no

const initialQuery = async () => {
  const first = db
   .collection("recipes-test")
   .orderBy("title")
   .startAfter(latestDoc || 0)
   .limit(10);

const data = await first.get();

  data.docs.forEach((doc) => {

   // console.log("doc.data", doc.data());

    dataArr.push(doc.data()); // pushing the data into the array
  });

 //! update latest doc
 latestDoc = data.docs[data.docs.length - 1];

 //! unattach event listeners if no more docs
 if (data.empty) {
  loadMore = false;
  }

 };

  // running this through this function so we can actual await for the 
  //docs to get from firebase
 const run = async () => {
  // looping until we get all the docs
     while (loadMore) {
      console.log({ loadMore });
      await initialQuery();
    }
  };

Upvotes: 0

Frank van Puffelen
Frank van Puffelen

Reputation: 599716

There is no flag in the response to indicate there are more documents. The common solution is to request one more document than you need/display, and then use the presence of that last document as an indicator that there are more documents.

This is also what the database would have to do to include such a flag in its response, which is probably why this isn't an explicit option in the SDK.

You might also want to check the documentation on keeping a distributed count of the number of documents in a collection as that's another way to determine whether you need to enable the UI to load a next page.

Upvotes: 3

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