how to get rank of each user in firestore

 

question

 

I use firestore to save user exam result.

I would like get rank of each user by exam type and date. How could i get it?

 

 

answer of chatgpt

 

To get the rank of each user by exam type and date in Firestore, you can use a combination of queries, aggregations, and snapshot listeners. Here's an example code snippet that shows how you can do this:

 

const db = firebase.firestore();
const collectionRef = db.collection('examResults');

// Query the collection for results of a specific exam type and date, sorted by score
const query = collectionRef
  .where('examType', '==', 'EXAM_TYPE')
  .where('examDate', '==', 'EXAM_DATE')
  .orderBy('score', 'desc');

// Attach a snapshot listener to the query
query.onSnapshot((querySnapshot) => {
  let rank = 1;
  let prevScore = null;
  querySnapshot.forEach((docSnapshot) => {
    const data = docSnapshot.data();
    if (prevScore !== data.score) {
      rank++;
      prevScore = data.score;
    }
    console.log(`User ${data.userId} has rank ${rank} with score ${data.score}`);
  });
});

 

In this code, the query variable is a reference to the collection filtered by a specific exam type and date, and sorted by score in descending order. Then, a snapshot listener is attached to the query, which will be triggered every time the collection is updated.

Inside the listener, a variable called rank is initialized to 1. Then, the listener iterates through each document in the query snapshot, incrementing the rank variable for each document with a different score. If two documents have the same score, they will have the same rank.

For each document, the user ID, score, and rank are printed to the console.

Note that in this example, the examType and examDate fields are hardcoded to a specific value. You can replace them with variables or input parameters to make the query more dynamic. Additionally, you may want to consider adding pagination or other techniques to handle large result sets

 

 

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firestore에서 사용자 랭킹 데이터 구할 수 있는지 궁금해서 chatgpt에 확인해본 결과이다.

아직 검증이 안되었고 나중에 확인해보려고 일단 저장해둔다. 

나중에 검증되면 여기를 업데이트하겠다.