嵌套Firestore集合上的Firestore地理查詢

按照教程 當我查詢任何位置時，我總是得到 0 結果，然后我嘗試查詢非嵌套集合（如教程視頻所示

嵌套集合的代碼（這是我的要求并且不起作用）

    public void queryHashes() {
    // Find cities within 50km of London
    final GeoLocation center = new GeoLocation(19.912524, 76.079626);
    final double radiusInM = 50 * 1000;

    // Each item in 'bounds' represents a startAt/endAt pair. We have to issue
    // a separate query for each pair. There can be up to 9 pairs of bounds
    // depending on overlap, but in most cases there are 4.
    List<GeoQueryBounds> bounds = GeoFireUtils.getGeoHashQueryBounds(center, radiusInM);
    final List<Task<QuerySnapshot>> tasks = new ArrayList<>();
    for (GeoQueryBounds b : bounds) {
        Query q = db.collection("Owners").document().collection("Ghars")
                .orderBy("geohash")
                .startAt(b.startHash)
                .endAt(b.endHash);

        tasks.add(q.get());
    }

    // Collect all the query results together into a single list
    Tasks.whenAllComplete(tasks)
            .addOnCompleteListener(new OnCompleteListener<List<Task<?>>>() {
                @Override
                public void onComplete(@NonNull Task<List<Task<?>>> t) {
                    List<DocumentSnapshot> matchingDocs = new ArrayList<>();

                    for (Task<QuerySnapshot> task : tasks) {
                        QuerySnapshot snap = task.getResult();
                        for (DocumentSnapshot doc : snap.getDocuments()) {
                            double lat = doc.getDouble("lat");
                            double lng = doc.getDouble("lng");

                            // We have to filter out a few false positives due to GeoHash
                            // accuracy, but most will match
                            GeoLocation docLocation = new GeoLocation(lat, lng);
                            double distanceInM = GeoFireUtils.getDistanceBetween(docLocation, center);
                            if (distanceInM <= radiusInM) {
                                matchingDocs.add(doc);
                            }
                        }
                    }

                    // matchingDocs contains the results
                    // ...
                    Log.v("matchingDocsD", matchingDocs.size() "");
                }
            });
}

非嵌套集合的代碼（有效）

    public void queryHashes() {
    // Find cities within 50km of London
    final GeoLocation center = new GeoLocation(19.912524, 76.079626);
    final double radiusInM = 50 * 1000;

    // Each item in 'bounds' represents a startAt/endAt pair. We have to issue
    // a separate query for each pair. There can be up to 9 pairs of bounds
    // depending on overlap, but in most cases there are 4.
    List<GeoQueryBounds> bounds = GeoFireUtils.getGeoHashQueryBounds(center, radiusInM);
    final List<Task<QuerySnapshot>> tasks = new ArrayList<>();
    for (GeoQueryBounds b : bounds) {
        Query q = db.collection("10K")
                .orderBy("geohash")
                .startAt(b.startHash)
                .endAt(b.endHash);

        tasks.add(q.get());
    }

    // Collect all the query results together into a single list
    Tasks.whenAllComplete(tasks)
            .addOnCompleteListener(new OnCompleteListener<List<Task<?>>>() {
                @Override
                public void onComplete(@NonNull Task<List<Task<?>>> t) {
                    List<DocumentSnapshot> matchingDocs = new ArrayList<>();

                    for (Task<QuerySnapshot> task : tasks) {
                        QuerySnapshot snap = task.getResult();
                        for (DocumentSnapshot doc : snap.getDocuments()) {
                            double lat = doc.getDouble("lat");
                            double lng = doc.getDouble("lng");

                            // We have to filter out a few false positives due to GeoHash
                            // accuracy, but most will match
                            GeoLocation docLocation = new GeoLocation(lat, lng);
                            double distanceInM = GeoFireUtils.getDistanceBetween(docLocation, center);
                            if (distanceInM <= radiusInM) {
                                matchingDocs.add(doc);
                            }
                        }
                    }

                    // matchingDocs contains the results
                    // ...
                    Log.v("matchingDocsD", matchingDocs.size() "");
                }
            });
}

uj5u.com熱心網友回復：

此查詢永遠不會回傳任何結果：

Query q = db.collection("Owners").document().collection("Ghars")
        .orderBy("geohash")
        .startAt(b.startHash)
        .endAt(b.endHash);

當您在document()沒有任何引數的情況下呼叫時，您正在創建對一個新的、不存在的檔案的參考。所以它的Ghars子集合也不存在，你的查詢沒有結果。

如果要查詢特定所有者的Ghars子集合，則應在呼叫中指定所有者的檔案 ID document()：

                                        // ??
Query q = db.collection("Owners").document(ownerDocId).collection("Ghars")
        .orderBy("geohash")
        .startAt(b.startHash)
        .endAt(b.endHash);

如果要查詢所有Ghars子集合，可以使用集合組查詢，它查詢具有特定名稱的所有集合：

                   // ??
Query q = db.collectionGroup("Ghars")
        .orderBy("geohash")
        .startAt(b.startHash)
        .endAt(b.endHash);

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