public async Task <ResponseModel> Read(string collectionId, HttpRequest request)
{
try
{
// A read request is either a request to "lookup by ID" or to "execute query".
var timer = new Stopwatch();
timer.Start();
var stream = new MemoryStream();
request.Body.CopyTo(stream);
var buf = stream.ToArray();
var skip = int.Parse(request.Query["skip"]);
var take = int.Parse(request.Query["take"]);
ResponseModel resultModel;
if (buf.Length == 0)
{
var ids = new List <long>();
foreach (var idParam in request.Query["id"])
{
var offset = long.Parse(idParam);
if (offset < 0)
{
throw new ArgumentOutOfRangeException("id");
}
var subResult = await _data.Read(collectionId.ToHash(), offset);
foreach (var x in subResult)
{
ids.Add(x);
}
}
var sorted = ids
.GroupBy(x => x)
.Select(x => (x.Key, x.Count()))
.OrderByDescending(x => x.Item2)
.ToList();
var window = sorted
.Skip(skip)
.Take(take == 0 ? sorted.Count : take)
.Select(x => x.Item1)
.ToList();
var streamResult = StreamRepository.Serialize(window.ToDictionary(x => x, y => 0f));
resultModel = new ResponseModel {
Stream = streamResult, MediaType = "application/postings", Total = sorted.Count
};
this.Log("processed read request for {0} postings in {1}", ids.Count, timer.Elapsed);
}
else
{
var queryHash = string.Format("{0}{1}{2}", Encoding.Unicode.GetString(buf), skip, take);
var key = queryHash.ToHash();
if (!_queryCache.TryGetValue(key, out resultModel))
{
var query = Query.FromStream(buf);
resultModel = await Reduce(collectionId.ToHash(), query, skip, take);
_queryCache.TryAdd(key, resultModel);
this.Log("executed query in {0}", timer.Elapsed);
}
}
return(resultModel);
}
catch (Exception ex)
{
this.Log(ex);
throw;
}
}
private async Task <ResponseModel> Reduce(ulong collectionId, IList <Query> query, int skip, int take)
{
IDictionary <long, float> result = null;
foreach (var q in query)
{
var cursor = q;
while (cursor != null)
{
var docIdList = await _data.Read(collectionId, cursor.PostingsOffsets);
var docIds = docIdList.ToDictionary(docId => docId, score => cursor.Score);
if (result == null)
{
result = docIds;
}
else
{
if (cursor.And)
{
var aggregatedResult = new Dictionary <long, float>();
foreach (var doc in result)
{
float score;
if (docIds.TryGetValue(doc.Key, out score))
{
aggregatedResult[doc.Key] = score + doc.Value;
}
}
result = aggregatedResult;
}
else if (cursor.Not)
{
foreach (var id in docIds.Keys)
{
result.Remove(id, out float _);
}
}
else // Or
{
foreach (var id in docIds)
{
float score;
if (result.TryGetValue(id.Key, out score))
{
result[id.Key] = score + id.Value;
}
else
{
result.Add(id.Key, id.Value);
}
}
}
}
cursor = cursor.Then;
}
}
var sortedByScore = result.ToList();
sortedByScore.Sort(
delegate(KeyValuePair <long, float> pair1,
KeyValuePair <long, float> pair2)
{
return(pair2.Value.CompareTo(pair1.Value));
}
);
if (take < 1)
{
take = sortedByScore.Count;
}
if (skip < 1)
{
skip = 0;
}
var window = sortedByScore.Skip(skip).Take(take);
var stream = StreamRepository.Serialize(window);
return(new ResponseModel {
Stream = stream, MediaType = "application/postings", Total = sortedByScore.Count
});
}