如何在附近运行地理“附近"用firestore查询? [英] How to run a geo "nearby" query with firestore?

问题描述

firebase中的新firestore数据库本身是否支持基于位置的地理位置查询?即找到10英里内的帖子，还是找到50个最近的帖子?

Does the new firestore database from firebase natively support location based geo queries? i.e. Find posts within 10 miles, or find the 50 nearest posts?

我看到实时Firebase数据库有一些现有项目，例如geofire，这些项目也可以改编成Firestore吗?

I see that there are some existing projects for the real-time firebase database, projects such as geofire- could those be adapted to firestore as well?

推荐答案

更新:Firestore当前不支持实际的GeoPoint查询，因此尽管以下查询成功执行，但它仅按纬度(而非经度)进行过滤，因此将返回许多不在附近的结果.最好的解决方案是使用 geohashes .要了解自己如何做类似的事情，请看以下视频.

UPDATE: Firestore does not support actual GeoPoint queries at present so while the below query executes successfully, it only filters by latitude, not by longitude and thus will return many results that are not nearby. The best solution would be to use geohashes. To learn how to do something similar yourself, have a look at this video.

这可以通过创建一个小于查询的边框来完成.至于效率，我不能说.

This can be done by creating a bounding box less than greater than query. As for the efficiency, I can't speak to it.

请注意，大约1英里的纬度/经度偏移的准确性应予以检查，但这是一种快速的方法:

Note, the accuracy of the lat/long offset for ~1 mile should be reviewed, but here is a quick way to do this:

SWIFT 3.0版本

func getDocumentNearBy(latitude: Double, longitude: Double, distance: Double) {

    // ~1 mile of lat and lon in degrees
    let lat = 0.0144927536231884
    let lon = 0.0181818181818182

    let lowerLat = latitude - (lat * distance)
    let lowerLon = longitude - (lon * distance)

    let greaterLat = latitude + (lat * distance)
    let greaterLon = longitude + (lon * distance)

    let lesserGeopoint = GeoPoint(latitude: lowerLat, longitude: lowerLon)
    let greaterGeopoint = GeoPoint(latitude: greaterLat, longitude: greaterLon)

    let docRef = Firestore.firestore().collection("locations")
    let query = docRef.whereField("location", isGreaterThan: lesserGeopoint).whereField("location", isLessThan: greaterGeopoint)

    query.getDocuments { snapshot, error in
        if let error = error {
            print("Error getting documents: \(error)")
        } else {
            for document in snapshot!.documents {
                print("\(document.documentID) => \(document.data())")
            }
        }
    }

}

func run() {
    // Get all locations within 10 miles of Google Headquarters
    getDocumentNearBy(latitude: 37.422000, longitude: -122.084057, distance: 10)
}

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