NHibernate - Tries to update entity that does not need to be updated

问题

so I have an entity named Event which contains many Reports (one to many) which contains many sources (many to many).

I'm facing a problem that I just cant figure out, when I'm trying to update my event, it will try to update the report because of the cascade (which is fine) and it will try to update the report's sources on the join table because of the cascade (which is fine), but for some reason it also tries to update the Source entity, which it shouldn't update because there is no change in it.

public class Event
{
    public virtual IList<Report> Reports { get; set; }
    public virutal int Id { get; set; }
    public Event()
    {
        Reports = new List<Report>();
    }
}

public class EventMapping : ClassMap<Event>
{
    public EventMapping()
    {
        Table("EVENTS");
        Id(x => x.Id).Column("ID").GeneratedBy.Sequence("EVENT_ID_SEQ");

        HasMany(x => x.Reports).KeyCoulmn("EVENT_ID").Cascade.SaveUpdate();
    }
}

public class Report
{
    public virtual int Id { get; set; }
    public virtual int Status { get; set; }
    public virtual IList<Source> Sources { get; set; }

    public Report()
    {
        Sources = new List<Source>();
    }
}

public class ReportMapping : ClassMap<Report>
{
    public ReportMapping()
    {
        Table("REPORTS");
        Id(x => x.Id).Column("ID").GeneratedBy.Sequence("DIVUACH_ID_SEQ");
        Map(x => x.Status).Column("Status");
        HasManyToMany(x => x.Sources).Table("SOURCES_IN_REPORT").ParentKeyColumn("REPORT_ID").ChildKeyColumn("KOD_SOURCE").Cascade.All();
    }
}

public class Source
{
    public virtual int Id { get; set; }
}

public class SourceMapping : ClassMap<Source>
{
    public SourceMapping()
    {
        Table("SOURCE");
        Id(x => x.Id).Column("ID");
    }
}

here is what I do and when it fails.

var eventFromDb = _session.Get<Event>(eventId);

eventFromDb.Reports.ToList().ForEach(x => x.Status = GetStatus());

_session.Update(eventFromDb);

Any idea why?

回答1:

Unwanted updates usually are cause be accidental changes of properties. NHibernate has automatic change tracking and updates all records when the properties do not return the exact same value that is assigned to it when loading.

See this answers:

Why hibernate always call "update" statement after using "select" statement in MySQL?
Nhibernate doing updates on select?

by the way, you do not need to call update(). NHibernate updates changed entities anyway when they are in the session. Everything you load from the database (e.g. by session.get() in your case) is in the session. Just commit the transaction.

来源：https://stackoverflow.com/questions/36422317/nhibernate-tries-to-update-entity-that-does-not-need-to-be-updated

标签

nhibernate

fluent-nhibernate

Cascade

jointable