[Lift] Re: Mapper: Is it possible to avoid the "n+1" selects?
On Tue, Aug 18, 2009 at 7:46 PM, David Pollak wrote: > > > On Tue, Aug 18, 2009 at 12:32 AM, Jeppe Nejsum Madsen > wrote: >> >> On Thu, Aug 13, 2009 at 5:12 PM, Derek Chen-Becker >> wrote: >> > You should be able to use the PreCache QueryParam to tell Mapper to >> > pre-fetch the mapped object: >> > >> > >> > http://scala-tools.org/scaladocs/liftweb/1.0/net/liftweb/mapper/PreCache.html >> >> Ok, time for a bonus question: Can this be extended to more than 1 level? > > You'd have to try it. ;-) Believe me, I tried :-) Couldn't really figure out what to use as parameter and looking at dealWithPrecache it seems like the two tables need to be directly linked It's not super critial atm, so I'll get back to this if necessary /Jeppe --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Lift" group. To post to this group, send email to liftweb@googlegroups.com To unsubscribe from this group, send email to liftweb+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/liftweb?hl=en -~--~~~~--~~--~--~---
[Lift] Re: Mapper: Is it possible to avoid the "n+1" selects?
On Tue, Aug 18, 2009 at 12:32 AM, Jeppe Nejsum Madsen wrote:
>
> On Thu, Aug 13, 2009 at 5:12 PM, Derek Chen-Becker
> wrote:
> > You should be able to use the PreCache QueryParam to tell Mapper to
> > pre-fetch the mapped object:
> >
> >
> http://scala-tools.org/scaladocs/liftweb/1.0/net/liftweb/mapper/PreCache.html
>
> Ok, time for a bonus question: Can this be extended to more than 1 level?
You'd have to try it. ;-)
I don't think Mapper officially supports multiple levels of precaching.
>
>
> I have something similar to the following
>
> class Vehicle extends LongKeyedMapper[Vehicle] with IdPK {
> object vehicleType extends MappedLongForeignKey(this, VehicleType)
> }
>
> class VehicleType extends LongKeyedMapper[VehicleType] with IdPK {
> object brand extends MappedLongForeignKey(this, Brand)
> }
>
> class Brand extends LongKeyedMapper[Brand] with IdPK {
> }
>
> When displaying the list of vehicles I need to show both the vehicle,
> the vehicleType & the brand in the same table
>
> So to get the list of vehicles and caching the vehicletypes I do this:
>
> override def findForListParams: List[QueryParam[Vehicle]] =
> List(By(account, User.currentUser.open_!.account.is),
> PreCache(vehicleType))
>
> But I still get the n+1 selects when trying to resolve
> vehicleType.brand. Can this be remedied somehow?
>
> /Jeppe
>
> >
>
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[Lift] Re: Mapper: Is it possible to avoid the "n+1" selects?
I don't think it currently supports it, but I'd have to look at the source
to give a definitive answer.
On Tue, Aug 18, 2009 at 1:32 AM, Jeppe Nejsum Madsen wrote:
>
> On Thu, Aug 13, 2009 at 5:12 PM, Derek Chen-Becker
> wrote:
> > You should be able to use the PreCache QueryParam to tell Mapper to
> > pre-fetch the mapped object:
> >
> >
> http://scala-tools.org/scaladocs/liftweb/1.0/net/liftweb/mapper/PreCache.html
>
> Ok, time for a bonus question: Can this be extended to more than 1 level?
>
> I have something similar to the following
>
> class Vehicle extends LongKeyedMapper[Vehicle] with IdPK {
> object vehicleType extends MappedLongForeignKey(this, VehicleType)
> }
>
> class VehicleType extends LongKeyedMapper[VehicleType] with IdPK {
> object brand extends MappedLongForeignKey(this, Brand)
> }
>
> class Brand extends LongKeyedMapper[Brand] with IdPK {
> }
>
> When displaying the list of vehicles I need to show both the vehicle,
> the vehicleType & the brand in the same table
>
> So to get the list of vehicles and caching the vehicletypes I do this:
>
> override def findForListParams: List[QueryParam[Vehicle]] =
> List(By(account, User.currentUser.open_!.account.is),
> PreCache(vehicleType))
>
> But I still get the n+1 selects when trying to resolve
> vehicleType.brand. Can this be remedied somehow?
>
> /Jeppe
>
> >
>
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[Lift] Re: Mapper: Is it possible to avoid the "n+1" selects?
On Thu, Aug 13, 2009 at 5:12 PM, Derek Chen-Becker wrote:
> You should be able to use the PreCache QueryParam to tell Mapper to
> pre-fetch the mapped object:
>
> http://scala-tools.org/scaladocs/liftweb/1.0/net/liftweb/mapper/PreCache.html
Ok, time for a bonus question: Can this be extended to more than 1 level?
I have something similar to the following
class Vehicle extends LongKeyedMapper[Vehicle] with IdPK {
object vehicleType extends MappedLongForeignKey(this, VehicleType)
}
class VehicleType extends LongKeyedMapper[VehicleType] with IdPK {
object brand extends MappedLongForeignKey(this, Brand)
}
class Brand extends LongKeyedMapper[Brand] with IdPK {
}
When displaying the list of vehicles I need to show both the vehicle,
the vehicleType & the brand in the same table
So to get the list of vehicles and caching the vehicletypes I do this:
override def findForListParams: List[QueryParam[Vehicle]] =
List(By(account, User.currentUser.open_!.account.is),
PreCache(vehicleType))
But I still get the n+1 selects when trying to resolve
vehicleType.brand. Can this be remedied somehow?
/Jeppe
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[Lift] Re: Mapper: Is it possible to avoid the "n+1" selects?
Derek Chen-Becker writes: > You should be able to use the PreCache QueryParam to tell Mapper to > pre-fetch the mapped object: > > http://scala-tools.org/scaladocs/liftweb/1.0/net/liftweb/mapper/PreCache.html Ahh nice. I missed that one, Thanks /Jeppe --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Lift" group. To post to this group, send email to liftweb@googlegroups.com To unsubscribe from this group, send email to liftweb+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/liftweb?hl=en -~--~~~~--~~--~--~---
[Lift] Re: Mapper: Is it possible to avoid the "n+1" selects?
You should be able to use the PreCache QueryParam to tell Mapper to pre-fetch the mapped object: http://scala-tools.org/scaladocs/liftweb/1.0/net/liftweb/mapper/PreCache.html Derek On Thu, Aug 13, 2009 at 6:11 AM, Jeppe Nejsum Madsen wrote: > > Hi > > I have a mapped object A with a foreign key to mapped object B. > > I need to display the information (A+B) in a table. The not so smart way > is to first query on the As and then for each A, get the B. This > results in n+1 selects. > > Is it possible to ask Mapper, when querying for the As, that it should > join with Bs table to fetch the B at the same time (ie the equivalent of > join fetching in Hibernate)? > > /Jeppe > > > > > > > --~--~-~--~~~---~--~~ You received this message because you are subscribed to the Google Groups "Lift" group. To post to this group, send email to liftweb@googlegroups.com To unsubscribe from this group, send email to liftweb+unsubscr...@googlegroups.com For more options, visit this group at http://groups.google.com/group/liftweb?hl=en -~--~~~~--~~--~--~---
