基于数组项的获取集合给出“FAILED_PRECONDITION：查询需要索引”。 [英] Fetch collection on basis of array item gives "FAILED_PRECONDITION: The query requires an index"

问题描述

我正在尝试获取所有带有maths标签的问题，但不是成功，而是转移到failedListener。

I am trying to fetch all questions which has "maths" tag, but instead of success it moves to failedListener.

db.collection("questionCollection")
                .orderBy("questionID", Query.Direction.DESCENDING)
                .whereArrayContains("tags","maths")
                .limit(3)
                .get()
                .addOnSuccessListener(new OnSuccessListener<QuerySnapshot>() {
                    @Override
                    public void onSuccess(QuerySnapshot queryDocumentSnapshots) {
                        if (queryDocumentSnapshots.isEmpty()) {
                            Log.d(TAG, "onSuccess: LIST EMPTY");
                            return;
                        } else {
                            // Convert the whole Query Snapshot to a list
                            // of objects directly! No need to fetch each
                            // document.
                            questionList = queryDocumentSnapshots.toObjects(QuestionBO.class);

                            if (questionList != null && questionList.size() > 0)
                                mAdapter.updateQuestions(questionList);
                        }
                    }
                }).addOnFailureListener(new OnFailureListener() {
            @Override
            public void onFailure(@NonNull Exception e) {
                e.printStackTrace();
                Toast.makeText(mContext,"Failed",Toast.LENGTH_LONG).show();
            }
        });

例外

FAILED_PRECONDITION: The query requires an index. You can create it here: https://console.firebase.google.com/project/testingproject-384af/database/firestore/indexes?create_index=EhJxd

推荐答案

只需单击该错误消息中提供给您的链接即可。它将带您进入控制台并要求您创建满足您尝试执行的查询的索引。

Just click the link given to you in that error message. It will take you to the console and ask you to create the index that will satisfy the query you're trying to perform.

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