[nhibernate-issues] [JIRA] Created: (NH-1090) Query cache does not work when using Criteria API to create a projection query with a result transformer

[NHibernate J. <mik...@us...>]

Query cache does not work when using Criteria API to create a projection qu=
ery with a result transformer
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                 Key: NH-1090
                 URL: http://jira.nhibernate.org/browse/NH-1090
             Project: NHibernate
          Issue Type: Bug
          Components: Core
    Affects Versions: 1.2.0.GA, 2.0.0.Alpha1, LATER
            Reporter: Olli Ryh=C3=A4nen
            Priority: Major


Enabling query-cache on a projection query with a result transformer attach=
ed using Criteria API, will fail with an exception:
"System.InvalidCastException: Unable to cast object of type '<The output ty=
pe from the result transformer' to type 'System.Object[]'"

The exception is caused by the line:
"cacheable.Add( TypeFactory.Disassemble( ( object[ ] ) result[ i ], returnT=
ypes, session ) );"
in "NHibernate\Cache\StandardQueryCache.cs" on line 63, when it tries to ca=
st the "result[i]" to an "object[]".

Using result transformers the result set has already been transformed to th=
e transformed type, before adding to the cache, so casting to "object[]" wi=
ll fail. (The transformation is done in the method "GetResultColumnOrRow" i=
n CriteriaLoader.cs on line 74, which gets called in process of loading the=
 result set from the database).

To reproduce the issue, turn on caching on any of the projection query test=
s with result transformer in "CriteriaQueryTests.cs". E.g. on line 494

IList resultWithAliasedBean =3D s.CreateCriteria(typeof (Enrolment))
   .CreateAlias("Student", "st")
   .CreateAlias("Course", "co")
   .SetProjection(Projections.ProjectionList()
         .Add(Projections.Property("st.Name"), "studentName")
         .Add(Projections.Property("co.Description"), "courseDescription")
   )
   .AddOrder(Order.Desc("studentName"))
   .SetResultTransformer(Transformers.AliasToBean(typeof (StudentDTO)))
   .SetCacheable(true)
   .List();
A simple fix would be to check if the type of "result[i]" is an "object[]" =
before adding to the cache and cache non "object[]" types as is to the cach=
e (and do the same check when getting the items back from the cache), but I=
'm not sure if that would break the caching architecture in some way.=20


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