/// <summary>
/// Merge continuous cells in cellUnion and return a list of merged GeohashRanges.
/// </summary>
/// <param name="cellUnion">Container for multiple cells.</param>
/// <returns>A list of merged GeohashRanges.</returns>
private static List <GeohashRange> MergeCells(S2CellUnion cellUnion)
{
var ranges = new List <GeohashRange>();
foreach (var c in cellUnion.CellIds)
{
var range = new GeohashRange(c.RangeMin.Id, c.RangeMax.Id);
var wasMerged = false;
foreach (var r in ranges)
{
if (r.TryMerge(range))
{
wasMerged = true;
break;
}
}
if (!wasMerged)
{
ranges.Add(range);
}
}
return(ranges);
}
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>
/// Query Amazon DynamoDB
/// </summary>
/// <param name="queryRequest"></param>
/// <param name="hashKey">Hash key for the query request.</param>
/// <param name="range">The range of geohashs to query.</param>
/// <returns>The query result.</returns>
public async Task <IReadOnlyList <QueryResponse> > QueryGeohashAsync(QueryRequest queryRequest, ulong hashKey, GeohashRange range, CancellationToken cancellationToken = default(CancellationToken))
{
if (queryRequest == null)
{
throw new ArgumentNullException("queryRequest");
}
if (range == null)
{
throw new ArgumentNullException("range");
}
var queryResults = new List <QueryResponse>();
IDictionary <String, AttributeValue> lastEvaluatedKey = null;
do
{
var keyConditions = new Dictionary <String, Condition>();
var hashKeyCondition = new Condition
{
ComparisonOperator = ComparisonOperator.EQ,
AttributeValueList = new List <AttributeValue>
{
new AttributeValue
{
N = hashKey.ToString(CultureInfo.InvariantCulture)
}
}
};
keyConditions.Add(_config.HashKeyAttributeName, hashKeyCondition);
var minRange = new AttributeValue
{
N = range.RangeMin.ToString(CultureInfo.InvariantCulture)
};
var maxRange = new AttributeValue
{
N = range.RangeMax.ToString(CultureInfo.InvariantCulture)
};
var geohashCondition = new Condition
{
ComparisonOperator = ComparisonOperator.BETWEEN,
AttributeValueList = new List <AttributeValue>
{
minRange,
maxRange
}
};
keyConditions.Add(_config.GeohashAttributeName, geohashCondition);
queryRequest.TableName = _config.TableName;
queryRequest.KeyConditions = keyConditions;
queryRequest.IndexName = _config.GeohashIndexName;
queryRequest.ConsistentRead = true;
queryRequest.ReturnConsumedCapacity = ReturnConsumedCapacity.TOTAL;
if (lastEvaluatedKey != null && lastEvaluatedKey.Count > 0)
{
queryRequest.ExclusiveStartKey[_config.HashKeyAttributeName] = lastEvaluatedKey[_config.HashKeyAttributeName];
queryRequest.ExclusiveStartKey[_config.RangeKeyAttributeName] = lastEvaluatedKey[_config.RangeKeyAttributeName];
queryRequest.ExclusiveStartKey[_config.GeohashAttributeName] = lastEvaluatedKey[_config.GeohashAttributeName];
}
QueryResponse queryResult = await _config.DynamoDBClient.QueryAsync(queryRequest, cancellationToken).ConfigureAwait(false);
queryResults.Add(queryResult);
lastEvaluatedKey = queryResult.LastEvaluatedKey;
} while (lastEvaluatedKey != null && lastEvaluatedKey.Count > 0);
return(queryResults);
}
