Cacheable(), FetchMany() and ToFuture() in same NHibernate Linq query

问题

Having a situation similar to the following example:

1 parent entity Employee having 2 child collections: Addresses and Phones

I need to retrieve in a single roundtrip all employees with their Addresses and Phones initialized and also cache the query that achieves that in level 2 cache using Cacheable().

Using:

var baseQuery = session
    .Query<Employee>()
    .Cacheable();

baseQuery
    .FetchMany(e => e.Addresses)
    .ToFuture();

var list = baseQuery
    .FetchMany(e => e.Phones)
    .ToFuture()
    .ToList();

should work, but I get the following exception:

NHibernate.PropertyAccessException

Message:

Exception occurred getter of NHibernateTest.Objects.Entity`1[[System.Int32, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]].Id

StackTrace:

at NHibernate.Properties.BasicPropertyAccessor.BasicGetter.Get(Object target) in p:\nhibernate-core\src\NHibernate\Properties\BasicPropertyAccessor.cs:line 213
at NHibernate.Tuple.Entity.AbstractEntityTuplizer.GetIdentifier(Object entity) in p:\nhibernate-core\src\NHibernate\Tuple\Entity\AbstractEntityTuplizer.cs:line 139
at NHibernate.Persister.Entity.AbstractEntityPersister.GetIdentifier(Object obj, EntityMode entityMode) in p:\nhibernate-core\src\NHibernate\Persister\Entity\AbstractEntityPersister.cs:line 3890
at NHibernate.Persister.Entity.AbstractEntityPersister.IsTransient(Object entity, ISessionImplementor session) in p:\nhibernate-core\src\NHibernate\Persister\Entity\AbstractEntityPersister.cs:line 3676
at NHibernate.Engine.ForeignKeys.IsTransient(String entityName, Object entity, Nullable`1 assumed, ISessionImplementor session) in p:\nhibernate-core\src\NHibernate\Engine\ForeignKeys.cs:line 194
at NHibernate.Engine.ForeignKeys.GetEntityIdentifierIfNotUnsaved(String entityName, Object entity, ISessionImplementor session) in p:\nhibernate-core\src\NHibernate\Engine\ForeignKeys.cs:line 250
at NHibernate.Type.ManyToOneType.Disassemble(Object value, ISessionImplementor session, Object owner) in p:\nhibernate-core\src\NHibernate\Type\ManyToOneType.cs:line 137
at NHibernate.Impl.MultipleQueriesCacheAssembler.Disassemble(Object value, ISessionImplementor session, Object owner) in p:\nhibernate-core\src\NHibernate\Impl\MultipleQueriesCacheAssembler.cs:line 33
at NHibernate.Cache.StandardQueryCache.Put(QueryKey key, ICacheAssembler[] returnTypes, IList result, Boolean isNaturalKeyLookup, ISessionImplementor session) in p:\nhibernate-core\src\NHibernate\Cache\StandardQueryCache.cs:line 74
at NHibernate.Impl.MultiQueryImpl.ListUsingQueryCache() in p:\nhibernate-core\src\NHibernate\Impl\MultiQueryImpl.cs:line 749
at NHibernate.Impl.MultiQueryImpl.List() in p:\nhibernate-core\src\NHibernate\Impl\MultiQueryImpl.cs:line 415
at NHibernate.Impl.FutureQueryBatch.GetResultsFrom(IMultiQuery multiApproach) in p:\nhibernate-core\src\NHibernate\Impl\FutureQueryBatch.cs:line 24
at NHibernate.Impl.FutureBatch`2.GetResults() in p:\nhibernate-core\src\NHibernate\Impl\FutureBatch.cs:line 73
at NHibernate.Impl.FutureBatch`2.get_Results() in p:\nhibernate-core\src\NHibernate\Impl\FutureBatch.cs:line 31
at NHibernate.Impl.FutureBatch`2.GetCurrentResult[TResult](Int32 currentIndex) in p:\nhibernate-core\src\NHibernate\Impl\FutureBatch.cs:line 79
at NHibernate.Impl.FutureBatch`2.<>c__DisplayClass4`1.<GetEnumerator>b__3() in p:\nhibernate-core\src\NHibernate\Impl\FutureBatch.cs:line 63
at NHibernate.Impl.DelayedEnumerator`1.<get_Enumerable>d__0.MoveNext() in p:\nhibernate-core\src\NHibernate\Impl\DelayedEnumerator.cs:line 26
at System.Collections.Generic.List`1..ctor(IEnumerable`1 collection)
at System.Linq.Enumerable.ToList[TSource](IEnumerable`1 source)
at Tests.Tests.CacheableFetchManyAndToFutureTest() in D:\somepath\Tests.cs:line 262

Inner exception:

System.Reflection.TargetException

Message:

Object does not match target type.

StackTrace:

at System.Reflection.RuntimeMethodInfo.CheckConsistency(Object target)
at System.Reflection.RuntimeMethodInfo.InvokeArgumentsCheck(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
at System.Reflection.RuntimeMethodInfo.Invoke(Object obj, BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
at System.Reflection.RuntimePropertyInfo.GetValue(Object obj, Object[] index)
at NHibernate.Properties.BasicPropertyAccessor.BasicGetter.Get(Object target) in p:\nhibernate-core\src\NHibernate\Properties\BasicPropertyAccessor.cs:line 207

Querying as following does not work since it generates a Cartesian product as a result which is ineffective. Having 1 employee with 2 addresses and 2 phones, each unique address and phone in the database would appear twice in Addresses and Phones collections. Making the results distinct after they are received at server is not a good option.

var list = session
    .Query<Employee>()
    .FetchMany(e => e.Addresses)
    .FetchMany(e => e.Phones)
    .Cacheable()
    .ToList();

Querying only with FetchMany() and ToFuture() (no Cacheable()) will return correctly all the employees with the corresponding addresses and phones (no duplicates) in 1 roundtrip but since the query is not cached there is no optimization for future identical requests:

var baseQuery = session
    .Query<Employee>();

baseQuery
    .FetchMany(e => e.Addresses)
    .ToFuture();

var list = baseQuery
    .FetchMany(e => e.Phones)
    .ToFuture()
    .ToList();

TLDR: How to retrieve all employees with addresses and phones initialized in a single roundtrip and have the query cached in level 2 cache? Thank you for replies!

来源：https://stackoverflow.com/questions/15437992/cacheable-fetchmany-and-tofuture-in-same-nhibernate-linq-query

标签

nhibernate

query-optimization

linq-to-nhibernate