[nhibernate-issues] [NHJIRA] Commented: (NH-2500) NH 3.0 Linq provider uses query parameters from first call in subsequent calls.

[Andrey T. (JIRA) <nh...@gm...>]

    [ http://216.121.112.228/browse/NH-2500?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=20509#action_20509 ] 

Andrey Titov commented on NH-2500:
----------------------------------

Please be aware in NHibernate-3.0.0.GA plans are cached by string key not containing types. So second queries in following pairs will throw InvalidCastException:

var cats = session.Query<Cat>().Select(cat => new CatInfo<string> { Name = cat.Name, SomeObject = "8989", }).ToList();
var cats = session.Query<Cat>().Select(cat => new CatInfo<int> { Name = cat.Name, SomeObject = 5675, }).ToList();

const string number = "3876";
var cats = session.Query<Cat>().Select(cat => number).ToList();
const int number = 4378;
var cats = session.Query<Cat>().Select(cat => number).ToList();

Two similar bugs were fixed: NH-2433 and NH-2459. I havn't check does this fix covers this scenario, but please take care to types when substityting constant values.

> NH 3.0 Linq provider uses query parameters from first call in subsequent calls.
> -------------------------------------------------------------------------------
>
>                 Key: NH-2500
>                 URL: http://216.121.112.228/browse/NH-2500
>             Project:  NHibernate
>          Issue Type: Bug
>          Components: Linq Provider
>    Affects Versions: 3.0.0.GA
>            Reporter: Andrey Titov
>            Assignee: Patrick Earl
>            Priority: Critical
>         Attachments: NH-2500.patch, NHTest3.zip
>
>
> NH 3.0 Linq provider uses query parameters from first call in subsequent calls if this parameters are not propagated to SQL.
> //in first session
> this.number = 545;
> var cats = session.Query<Cat>().Select(cat => new CatInfo { Name = cat.Name, SomeNumber = this.number }).ToList();
> // all works perfect: all CatInfos contains 545
> //later in another session
> this.number = 842;
> var cats = session.Query<Cat>().Select(cat => new CatInfo { Name = cat.Name, SomeNumber = this.number }).ToList();
> // magic happens: all CatInfos contains 545 again
> I've debugged NH and found that in second query it gets QueryPlan from cache in NHibernate.Impl.AbstractSessionImpl.GetHQLQueryPlan() and it contains parameters from first call of query (NHibernate.Linq.NhLinqExpression.ParameterValuesByName) and then fails to replace them in NHibernate.Linq.NhQueryProvider.SetParameters() because they are not actual SQL parameters (query.NamedParameters).
> Sample solution is attached (VS2010, SQL Server Express DB). Put NH and LinFu.DynamicProxy binaries to .Libraries\NHibernate before build.
> I think actual parameters should be cleared from query (set to default(T)) before putting plan in QueryPlanCache to let them be garbage collected and prevent real magic happen in case of similar bugs.

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