FutureValue fails on Linq queries defining a PostExecuteTransformer
Description
When a FutureValue has to call its ExecuteOnEval delegate, it fails with an unable to convert exception from a scalar/entity to a IQueryable of the scalar/entity.
Current 5.0.0 code base seems to affect ExecuteOnEval only when Value is obtained from First/FirstOrDefault/Single/SingleOrDefault, like in session.Query<DomainClass>().Select(e => e.Id).ToFutureValue(q => q.FirstOrDefault()).Value This is done by ProcessFirstOrSingleBase from ResultOperatorProcessors namespace. It defines a PostExecuteTransformer on the IntermediateHqlTree taking an IQueryable as input and yielding the scalar/entity as output. This transformer ends up affected to ExecuteOnEval.
But current implementation of FutureValue call ExecuteOnEval on a scalar/entity value instead of an IQueryable.
This trouble was discovered while attempting to solve NH-3850. (The solution I am working on for this other bug involves adding PostExecuteTransformer for scalar queries like Count/Min/Max/Sum, which has caused some FutureValue tests to start failing due to this bug with FutureValue and PostExecuteTransformer.)
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Frédéric Delaporte February 22, 2017 at 1:33 AM
Edited
Well, rebasing my forked master was easy, but then rebasing my branch was yielding an ugly history, I have ended up merging. (I am not used to git.)
When a
FutureValuehas to call itsExecuteOnEvaldelegate, it fails with an unable to convert exception from a scalar/entity to aIQueryableof the scalar/entity.Current 5.0.0 code base seems to affect
ExecuteOnEvalonly when Value is obtained fromFirst/FirstOrDefault/Single/SingleOrDefault, like insession.Query<DomainClass>().Select(e => e.Id).ToFutureValue(q => q.FirstOrDefault()).ValueThis is done by
ProcessFirstOrSingleBasefromResultOperatorProcessorsnamespace. It defines aPostExecuteTransformeron theIntermediateHqlTreetaking anIQueryableas input and yielding the scalar/entity as output. This transformer ends up affected toExecuteOnEval.But current implementation of
FutureValuecallExecuteOnEvalon a scalar/entity value instead of anIQueryable.This trouble was discovered while attempting to solve NH-3850. (The solution I am working on for this other bug involves adding
PostExecuteTransformerfor scalar queries likeCount/Min/Max/Sum, which has caused someFutureValuetests to start failing due to this bug withFutureValueandPostExecuteTransformer.)