> eh?!??!??
> NH ha to workaround RDBMS issue.
> NH have to work around to commercial companies visual components.
hahaha :D. Trust me, I really had the same reaction initially :)
Especially when I found out my linq provider crashed always, with every
query created by DevExpress' linqdatasource because they were always
grouping on a constant value (e.g. 0).
but what can you do: the user wants to use the grid, the linq
datasource or whtever control the ui control vendor cooks up to produce linq
stuff, and if the o/r mapper doesn't work that way, the user will likely
look elsewhere to use something which does work with the grid. Sadly, o/r
mapper developers are in that tough spot where all the problems of other
people are supposed to be solved. ;).
In the end, it's not that hard really. It's just similar to the
VB.NET stuff: you'll find out along the way, which is of course a sucky
situation, but alas, our destiny as o/r mapper developers ;)
FB
>
> Something else ?
> a coffee ?
>
> On Fri, Jul 23, 2010 at 5:42 AM, Frans Bouma <[email protected]> wrote:
>
>
> > Ok, I think I should explain a little further. I'm using a third-
> party
> > control (Trirand's jqgrid MVC control) which accepts an
> IQueryable<T>, and
> > using Reflector have worked out that this is the kind of call they
> are
> > making.
> >
> > I agree that doing a ToList() then Count() would give the correct
> result,
> > and arguably this control should be rewritten to do this (since
> they are
> > subsequently calling ToList() anyway). However I don't have
access
> to
> their
> > code and besides it seems to me that just calling Count() should
> work as
> > expected.
>
>
> knowing that the DevExpress' grid with their linqdatasource
> creates
> complex linq queries with much more complex issues than the one you
> posted,
> (like grouping on a constant :)), it's inevitable to simply support
> these
> constructs, otherwise people will simply not use the linq provider
> (and that
> would be a waste of effort).
>
> the query you reported is a valid linq query, it should
> produce the
> query you expected, so I'd opt for filing a bug report, but it's up
> to Steve
> (where's Steve anyway? ;)) if he has time to fix this.
>
> The 'ToList()' workaround is silly really, you don't want to
> fetch
> all data to do an aggregate in-memory
>
>
> > Should I log this as a bug somewhere??
>
>
> you can log issues here: http://216.121.112.228
>
> FB
>
>
> >
> > Thanks very much for your replies.
> >
> > Alastair
> >
> >
> >
> >
> >
> > On Jul 23, 8:27 am, "Frans Bouma" <[email protected]> wrote:
> > > > Nobody knows which is the real target of the query... well...
> nobody...
> > > > perhaps the user knows.
> > > > Wherever you put the Count() I can't understand the sense.
> > >
> > > of course the real target is known: it's the result of
> the
> > > Take() method. Skip & Take are query modifiers, not real query
> > > returning methods ('query' in the sense of a select statement).
> The
> > > source of skip is a query, so skip & take modify that query and
> it then
> > becomes the source of count.
> > >
> > > Same sort of query:
> > > session.Linq<Foo>().Count(c=>c.SomeField=="Bar");
> > >
> > > here no skip/take is present, but as these are query
> > > modifiers, it's not really a different construct: you have a
> query and
> > > it's used as the source of the aggregate.
> > >
> > > FB
> > >
> > >
> > >
> > >
> > >
> > >
> > >
> > > > On Thu, Jul 22, 2010 at 3:20 PM, Frans Bouma <[email protected]>
> wrote:
> > >
> > > > > I'm trying to perform this query on NHibernate 2.1.2 with
> > > > NHibernate.Linq
> > > > > (1.1.0.1001)
> > >
> > > > > session.Linq<FieldStructure>().Skip(10).Take(10).Count()
> > >
> > > > > This generates the following SQL
> > >
> > > > > "NHibernate: SELECT TOP 10 y0_ FROM (SELECT count(*) as
> y0_,
> > > > > ROW_NUMBER() OVER(ORDER BY CURRENT_TIMESTAMP) as
> > > > __hibernate_sort_row FROM
> > > > > FieldStructure this_) as query WHERE
> query.__hibernate_sort_row
> > > > >
> > > > > 10 ORDER BY query.__hibernate_sort_row"
> > >
> > > > > This query always returns 0 rows, I know I should be
> getting 10
> > > > rows.
> > >
> > > > > If I perform the same query without the Count(), I will
> get 10
> > > > rows.
> > > > > The SQL generated is...
> > >
> > > > > "NHibernate: SELECT TOP 10 <list of fields>, ROW_NUMBER()
> > > > OVER(ORDER BY
> > > > > CURRENT_TIMESTAMP) as __hibernate_sort_row FROM
> FieldStructure
> > > > this_ left
> > > > > outer join Lookup lookup2_ on
> > > > > this_.LookupId=lookup2_.LookupId) as query WHERE
> > > > query.__hibernate_sort_row
> > > > > > 10 ORDER BY query.__hibernate_sort_row"
> > >
> > > > > Is this a bug?
> > >
> > > > Looks like it. The link provider apparently sees the
> > > aggregate
> > > > expression as the outer query, but that shouldn't be done
> that way:
> > > > the skip
> > > > and take expressions are consumed by an expression visitor
> but
> > > > the values
> > > > they get as parameters should be applied to the query /
> sequence
> > > they
> > > > work
> > > > on, and _that_ sequence is then the source of the aggregate
> > > > expression,
> > > > which always works on a separate scope, so it could never
be
> > > > wrapped by a
> > > > take.
> > >
> > > > FB
> > >
> > > > --
> > > > Fabio Maulo- Hide quoted text -
> > >
> > > - Show quoted text-
>
>
>
>
>
>
> --
> Fabio Maulo
>
