Executing an Aggregation

Executing an aggregation is a lot like doing a standard search, except we'll be using the RediSearchAggregateQuery builder in order to create the aggregation query and then using the Aggregate or AggregateAsync extension methods to invoke the actual aggregation.

The following example demonstrates

var zipCodeCountByProximity = RediSearchAggregateQuery.On("zips")
    .Query("@Coordinates:[-87.320330 30.423090 10 mi]")
    .GroupBy(gb =>
    {
        gb.Fields("@City");
        gb.Reduce(Reducer.Count).As("Count");
    })
    .SortBy(sb => 
    {
        sb.Field("@City", Direction.Ascending);
        sb.Field("@Count", Direction.Descending);
        sb.Max(100);
    })
    .Build();

var result = await _db.AggregateAsync(zipCodeCountByProximity);

Handling the Result

The result from the above aggregation query of the zip code data in the sample zipcodes index will yield an instance of the AggregateResult class. The AggregateResult class is an implementation of the IEnumerable<AggregateResultCollection>. The AggregateResultCollection is an abstraction on top of a collection of KeyValuePair<string, RedisResult> which gives us the ability to easily access the fields for each "row" in the result set.

The following example demonstrates handling the result from the "Executing an Aggregation" sample above and projecting it into an anonymous type:

var result = await _db.AggregateAsync(zipCodeCountByProximity);

var cityZipCodes = result.Select(x => new
{
    City = (string)x["City"],
    Count = (int)x["Count"]
});

Mapping the Result

See this documentation for defining a type mapping.

With the appropriate mapping defined you can now map the result like...

var result = await _db.AggregateAsync(zipCodeCountByProximity);

var mappedResult = result.As<CityCount>();

The variable mappedResult will be of type IEnumerable<CityCount>.