alkampfergit

.....

//this filters result of the query, then apply aggregations on terms. 
//if you want to filter result of the aggregation you will need reducers
//https://github.com/elasticsearch/elasticsearch/issues/8110
 .Aggregations(a1 => a1
     .Filter("filter", fd => fd.Filter(f => 
         f.Regexp(f3 => f3
             .OnField(d => d.MdFacets)
             .Value(parameters.FacetName + @"\|.*"))

alkampfergit

 db.Commits.aggregate([
    {$sort: {_id:1}},
    {$unwind : "$Events"},
    {$project : { event : '$Events.Payload.Body._t'}},
    {$group : {
        '_id' : '$event', 
        'count' : {$sum : 1}}
    }
])