Question

The following nhibernate query is causing me issues because it returns the same row more that once as the child tables have more than one row that match the criteria supplied. What i would like to know is the most efficient/ best practice in nhibernate to do this same query but to only get each row in DataMappingBase once. Returning multiple of the same row is breaking my number of results returned as i try to limit it 25 but sometimes i get the same row 25 times.

MappedID id = null;
DataMappingBase mapBase = null;
NameDetails name = null;
dmbs = mappingSession.QueryOver<DataMappingBase>(() => mapBase)
   .JoinAlias(() => mapBase.IDs, () => id).WhereRestrictionOn(() => id.SecondaryDataIDType).IsNull()
   .JoinAlias(() => mapBase.Names, () => name).WhereRestrictionOn(() => name.Name).IsInsensitiveLike(request.Filter, MatchMode.Anywhere)
   .Take(request.MaxResults)
   .List();

i am currently looking at converting the query above to a detached query and removing the “take” clause and getting it to just return the ID of the matching rows and have it used in a sub-query selecting from “DataMappingBase” where the rows ID is in the ids returned by the sub-query but i am not sure if that is the best way or not.

Answer 1

I’m not sure, but you can do like this:

MappedID id = null;
DataMappingBase mapBase = null;
NameDetails name = null;
dmbs = mappingSession.QueryOver<DataMappingBase>(() => mapBase)
   .JoinAlias(() => mapBase.IDs, () => id).WhereRestrictionOn(() => id.SecondaryDataIDType).IsNull()
   .JoinAlias(() => mapBase.Names, () => name).WhereRestrictionOn(() => name.Name).IsInsensitiveLike(request.Filter, MatchMode.Anywhere)
   .Take(request.MaxResults)
   // add this
   .TransformUsing(Transformers.DistinctRootEntity)
   .List();