Pseudocode:
var receipts = LinqCriteriaSqlOrHqlQueryForReceiptsOnly()
.FilteringByIsNotSynchronizedAndIsClosed()
.InAnyOrderThatYouWant()
.SetMaxResults(200) // or .Take(200) for Linq
.List<Receipt>()
var ids = (from receipt in receipts select receipt.Id).ToList();
var irrelevant = QueryForReceiptsFetchingPayments()
.FilteringByIdIn(ids)
.List()
var irrelevantToo = QueryForReceiptsFetchingEntries()
.YouGetTheIdea()
.YouCanCombineTheseTwoQueriesWithFuture()
Now, if you are going to use WFC, it's better to create DTOs, regardless of
how you do the queries.
Diego
On Mon, Aug 30, 2010 at 05:48, Niclas Pehrsson <[email protected]> wrote:
> Well its a lot.
>
> Receipt has two collections, receipt entries and payments.
> I want to load top 200 where the receipts is closed and not
> synchronized.
> The entities will be sent over wcf so lazyloading isn't anything to
> use it is best to load them all at the same time.
> We are using NHibernate 2.1 right now.
>
> Receipt.IsSynchronized
> Receipt.IsClosed
> Receipt.Payments
> Receipt.Entries
>
> How would I do this on the most efficient way?
>
> On Aug 28, 12:55 pm, Diego Mijelshon <[email protected]> wrote:
> > ONE QUERY PER COLLECTION, not ONE QUERY PER COLLECTION PER RECORD.
> > If you have one filtered query with two collections, that's 3 queries
> TOTAL,
> > regardless of the record count.
> >
> > Future allows you to reduce the roundtrips (the number of queries is
> still
> > the same), but you can't combine the first query and the others if you're
> > paging.
> > You can still use it for queries other than the first, which brings the
> > roundtrip count to 2 regardless of how many collections or records you
> are
> > loading.
> >
> > Diego
> >
> > On Sat, Aug 28, 2010 at 04:55, Niclas Pehrsson <[email protected]>
> wrote:
> > > Well that means a lot of queries if MaxSize is 200.
> > > But maybe it is the only way to do it.
> >
> > > Are there any example of this scenario with Criterion?
> > > I guess the use of Future is needed, you want to get the root entity
> > > loaded with its collections as result.
> >
> > > On Aug 27, 8:08 pm, Diego Mijelshon <[email protected]> wrote:
> > > > The answer is right there: "two totally separate queries, first to
> get
> > > just
> > > > the entities, then to load the related associations"
> >
> > > > First, one paged query without fetching the collections, then one
> query
> > > per
> > > > collection, filtering with the Ids of the first query.
> >
> > > > Diego
> >
> > > > On Fri, Aug 27, 2010 at 09:49, Niclas Pehrsson <[email protected]>
> > > wrote:
> > > > > Well it wont work :(
> >
> > > > > Ayende repsonded to an comment with this
> > > > > "SetMaxResults, but that might cause issues with the loading.
> > > > > At that point, I might want to execute two totally separate
> queries,
> > > > > first to get just the entities, then to load the related
> associations.
> > > > > "
> >
> > > > > So how can I solve this?
> > > > > Its a bit annoying, I want to load 200 hundred of thousands, and I
> > > > > want to avoid 200+200 select queries.
> > > > > Any other approaches?
> >
> > > > > On Aug 26, 3:03 pm, Diego Mijelshon <[email protected]>
> wrote:
> > > > > > SetMaxResults and SetFetchMode on _collections_ don't get along.
> >
> > > > > > Suggested read:
> > > > >
> http://ayende.com/Blog/archive/2010/01/16/eagerly-loading-entity-asso.
> > > ..
> >
> > > > > > Diego
> >
> > > > > > On Thu, Aug 26, 2010 at 04:50, Niclas Pehrsson <
> [email protected]>
> > > > > wrote:
> > > > > > > Hi I have an query that looks like this.
> >
> > > > > > > Return (From receipt In _session.Linq(Of
> > > > > > > PointOfSale.Receipt)() _
> > > > > > > Where receipt.IsClosed AndAlso Not
> > > > > > > receipt.IsSynchronized _
> > > > > > > Select receipt).Take(25).ToList()
> >
> > > > > > > Or
> > > > > > > Dim criterion = _session.CreateCriteria(Of Receipt)
> > > > > > > ().SetMazSize(25).Add(Expression.Eq("IsClosed", True)) _
> > > > > > > .Add(Expression.Eq("IsSynchronized", False)) _
> > > > > > > .SetFetchMode("Payments", FetchMode.Eager) _
> > > > > > > .SetFetchMode("ReceiptEntry", FetchMode.Eager)
> >
> > > > > > > 'Return criterion.List(Of PointOfSale.Receipt)()
> >
> > > > > > > Both of them first asks the database för the first query
> options
> > > > > > > IsClosed and Not IsSynchronized, and then It creates an select
> N+1
> > > for
> > > > > > > each element. How can I do this better so it will be just one
> or
> > > three
> > > > > > > queries that selects top 25 entities?
> >
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