NHibernate fluent (QueryOver) replacement for HQL with correlated subquery

Question

Background, using FluentNHibernate, lastest dev build working with NHibernate 3.0.

Here is the type declarations for WorkIncident:

// Enumeration used in class below.
public enum TicketStatus
{
    Open = 1,
    Closed = 10,
    Hold = 20
}

// Ticket class.
public class WorkIncident
{
    public virtual int EntryId { get; set; }
    public virtual int TicketNumber { get; set; }
    public virtual string ModifierNtId { get; set; }
    public virtual DateTime ModifiedDate { get; set; }
    public virtual TicketStatus Status { get; set; }
    public virtual int Version { get; set; }
    public virtual string Title { get; set; }
    public virtual string Details { get; set; }
}

// FluentNHibernate mapping
public class WorkIncidentMap : ClassMap<WorkIncident>
{
    public WorkIncidentMap()
    {
        Table("incident_details");
        Id( wi => wi.EntryId, "wiid");
        Map(wi => wi.TicketNumber, "workitem_number");
        Map(wi => wi.Title, "workitem_title");
        Map(wi => wi.Details, "workitem_comment");
        Map(wi => wi.ModifiedDate, "workitem_modified_on");
        Map(wi => wi.ModifierNtId, "modified_by_worker_nt_id");
        Map(wi => wi.Status, "workitem_status_lookup_id").CustomType<EnumType<Status>>();
        Map(wi => wi.Version, "workitem_version");
    }
}

The mapping works fine, and I can do queries like the following with no problems:

session.QueryOver<AltirisIncident>()
    .Where(ai => ai.ModifierNtId == worker.Name.Replace("\\", @"\"))
    .AndRestrictionOn(ai => ai.ModifiedDate)
    .IsBetween(DateTime.Today)
    .And(DateTime.Today.AddDays(1))
    .List<WorkIncident>();

This gives me all of the work items (basically help desk trouble tickets) touched by a specific user on the current date.

However, I have been having trouble translating the following HQL into a fluent declaration:

from    WorkIncident as t1
where   t1.ModifierNtId = :ntid
and     t1.ModifiedDate between :startdate and :enddate
and     t1.Status = :status
and     (t1.Version = 1
or      t1.TicketNumber in (
    select    t2.TicketNumber
    from      WorkIncident as t2
    where     t2.Status != t1.Status
    and       t2.TicketNumber = t1.TicketNumber
    and       t2.Version = t1.Version - 1))

This query gives me the list of all work items that were placed in a closed status by a worker. Given the way the tickets are stored in the database (each ticket has multiple records (one for each update) and supervisors will often add notes to a ticket after a worker has closed it, leads to situations where I can't just look at the last version number with a closed status to reliably tell me who closed a ticket.

Any help would be greatly appreciated, as I would prefer to move away from HQL and magic strings as much as possible.

Answer 1

I think this should do the trick. The tough part is really handling that mathematical operation you've got there. You have to get into SQLFunction projections

session.QueryOver<WorkIncident>(() => t1Alias)
                .Where(w => w.ModifierNtId == "test")
                .And(w => w.ModifiedDate < DateTime.Now && w.ModifiedDate > DateTime.Now)
                .And(w => w.Status == TicketStatus.Open)
                .And(Restrictions.Disjunction()
                    .Add(Restrictions.Where<WorkIncident>(w => w.TicketNumber == 1))
                    .Add(Subqueries.WhereProperty(() => t1Alias.TicketNumber).In(
                        QueryOver.Of<WorkIncident>(() => t2Alias)
                                .Where(() => t2Alias.Status != t1Alias.Status)
                                .And(() => t2Alias.TicketNumber == t1Alias.TicketNumber)
                                .And(Restrictions.EqProperty(
                                    Projections.Property<WorkIncident>(w=> w.Version), 
                                    Projections.SqlFunction(
                                        new VarArgsSQLFunction("(","-",")"),
                                        NHibernateUtil.Int32,
                                        Projections.Property(()=> t1Alias.Version),
                                        Projections.Constant(1)
                                    )))
                                .Select(w => w.TicketNumber)))
                ).List();

In my test, this generated the following SQL

 SELECT <snip...>
 FROM incident_details this_ 
 WHERE this_.modified_by_worker_nt_id = @p0 
    and (this_.workitem_modified_on < @p1 and this_.workitem_modified_on > @p2) 
    and this_.workitem_status_lookup_id = @p3 
    and (this_.workitem_number = @p4 
    or this_.workitem_number in 
        (SELECT this_0_.workitem_number as y0_ 
         FROM incident_details this_0_ 
         WHERE not (this_0_.workitem_status_lookup_id = this_.workitem_status_lookup_id) 
         and this_0_.workitem_number = this_.workitem_number 
         and this_0_.workitem_version = (this_.workitem_version-@p5)));
         @p0 = 'test' [Type: String (0)], @p1 = 10/26/2012 11:26:24 PM [Type: DateTime (0)], @p2 = 10/26/2012 11:26:24 PM [Type: DateTime (0)], @p3 = 1 [Type: Int32 (0)], @p4 = 1 [Type: Int32 (0)], @p5 = 1 [Type: Int32 (0)]