/// <summary>
/// Filter out any points outside of the queried area from the input list.
/// </summary>
/// <param name="list">List of items return by Amazon DynamoDB. It may contains points outside of the actual area queried.</param>
/// <param name="geoQueryRequest">List of items within the queried area.</param>
/// <returns></returns>
private IEnumerable <IDictionary <string, AttributeValue> > Filter(IEnumerable <IDictionary <string, AttributeValue> > list,
GeoQueryRequest geoQueryRequest)
{
var result = new List <IDictionary <String, AttributeValue> >();
S2LatLngRect?latLngRect = null;
S2LatLng? centerLatLng = null;
double radiusInMeter = 0;
if (geoQueryRequest is QueryRectangleRequest)
{
latLngRect = S2Util.GetBoundingLatLngRect(geoQueryRequest);
}
foreach (var item in list)
{
var geoJson = item[_config.GeoJsonAttributeName].S;
var geoPoint = GeoJsonMapper.GeoPointFromString(geoJson);
var latLng = S2LatLng.FromDegrees(geoPoint.lat, geoPoint.lng);
if (latLngRect != null && latLngRect.Value.Contains(latLng))
{
result.Add(item);
}
else if (centerLatLng != null && radiusInMeter > 0 &&
centerLatLng.Value.GetEarthDistance(latLng) <= radiusInMeter)
{
result.Add(item);
}
}
return(result);
}
/// <summary>
/// An utility method to get a bounding box of latitude and longitude from a given GeoQueryRequest.
/// </summary>
/// <param name="geoQueryRequest">It contains all of the necessary information to form a latitude and longitude box.</param>
/// <returns></returns>
public static S2LatLngRect GetBoundingLatLngRect(GeoQueryRequest geoQueryRequest)
{
if (geoQueryRequest is QueryRectangleRequest)
{
var queryRectangleRequest = (QueryRectangleRequest)geoQueryRequest;
var minPoint = queryRectangleRequest.MinPoint;
var maxPoint = queryRectangleRequest.MaxPoint;
var latLngRect = default(S2LatLngRect);
if (minPoint != null && maxPoint != null)
{
var minLatLng = S2LatLng.FromDegrees(minPoint.Latitude, minPoint.Longitude);
var maxLatLng = S2LatLng.FromDegrees(maxPoint.Latitude, maxPoint.Longitude);
latLngRect = new S2LatLngRect(minLatLng, maxLatLng);
}
return(latLngRect);
}
else if (geoQueryRequest is QueryRadiusRequest)
{
var queryRadiusRequest = (QueryRadiusRequest)geoQueryRequest;
var centerPoint = queryRadiusRequest.CenterPoint;
var radiusInMeter = queryRadiusRequest.RadiusInMeter;
var centerLatLng = S2LatLng.FromDegrees(centerPoint.Latitude, centerPoint.Longitude);
var latReferenceUnit = centerPoint.Latitude > 0.0 ? -1.0 : 1.0;
var latReferenceLatLng = S2LatLng.FromDegrees(centerPoint.Latitude + latReferenceUnit,
centerPoint.Longitude);
var lngReferenceUnit = centerPoint.Longitude > 0.0 ? -1.0 : 1.0;
var lngReferenceLatLng = S2LatLng.FromDegrees(centerPoint.Latitude, centerPoint.Longitude
+ lngReferenceUnit);
var latForRadius = radiusInMeter / centerLatLng.GetEarthDistance(latReferenceLatLng);
var lngForRadius = radiusInMeter / centerLatLng.GetEarthDistance(lngReferenceLatLng);
var minLatLng = S2LatLng.FromDegrees(centerPoint.Latitude - latForRadius,
centerPoint.Longitude - lngForRadius);
var maxLatLng = S2LatLng.FromDegrees(centerPoint.Latitude + latForRadius,
centerPoint.Longitude + lngForRadius);
return(new S2LatLngRect(minLatLng, maxLatLng));
}
return(S2LatLngRect.Empty);
}
private async Task RunGeoQuery(GeoQueryRequest request, GeoQueryResult geoQueryResult, GeohashRange range, CancellationToken cancellationToken)
{
var queryRequest = request.QueryRequest.CopyQueryRequest();
var hashKey = S2Manager.GenerateHashKey(range.RangeMin, _config.HashKeyLength);
var results = await _dynamoDBManager.QueryGeohashAsync(queryRequest, hashKey, range, cancellationToken).ConfigureAwait(false);
foreach (var queryResult in results)
{
cancellationToken.ThrowIfCancellationRequested();
// This is a concurrent collection
geoQueryResult.QueryResults.Add(queryResult);
var filteredQueryResult = Filter(queryResult.Items, request);
// this is a concurrent collection
foreach (var r in filteredQueryResult)
{
geoQueryResult.Items.Add(r);
}
}
}
/// <summary>
/// An utility method to get a bounding box of latitude and longitude from a given GeoQueryRequest.
/// </summary>
/// <param name="geoQueryRequest">It contains all of the necessary information to form a latitude and longitude box.</param>
/// <returns></returns>
public static S2LatLngRect GetBoundingLatLngRect(GeoQueryRequest geoQueryRequest)
{
if (geoQueryRequest is QueryRectangleRequest)
{
var queryRectangleRequest = (QueryRectangleRequest)geoQueryRequest;
var minPoint = queryRectangleRequest.MinPoint;
var maxPoint = queryRectangleRequest.MaxPoint;
var latLngRect = default(S2LatLngRect);
if (minPoint != null && maxPoint != null)
{
var minLatLng = S2LatLng.FromDegrees(minPoint.lat, minPoint.lng);
var maxLatLng = S2LatLng.FromDegrees(maxPoint.lat, maxPoint.lng);
latLngRect = new S2LatLngRect(minLatLng, maxLatLng);
}
return(latLngRect);
}
return(S2LatLngRect.Empty);
}
private async Task <GeoQueryResult> DispatchQueries(IEnumerable <GeohashRange> ranges, GeoQueryRequest geoQueryRequest, CancellationToken cancellationToken)
{
var geoQueryResult = new GeoQueryResult();
var futureList = new List <Task>();
var internalSource = new CancellationTokenSource();
var internalToken = internalSource.Token;
var cts = CancellationTokenSource.CreateLinkedTokenSource(cancellationToken, internalToken);
foreach (var outerRange in ranges)
{
foreach (var range in outerRange.TrySplit(_config.HashKeyLength))
{
var task = RunGeoQuery(geoQueryRequest, geoQueryResult, range, cts.Token);
futureList.Add(task);
}
}
Exception inner = null;
try
{
for (var i = 0; i < futureList.Count; i++)
{
try
{
await futureList[i].ConfigureAwait(false);
}
catch (Exception e)
{
inner = e;
// cancel the others
internalSource.Cancel(true);
}
}
}
catch (Exception ex)
{
inner = inner ?? ex;
throw new ClientException("Querying Amazon DynamoDB failed.", inner);
}
return(geoQueryResult);
}
