Hi Tomas,
On Wed, Apr 22, 2009 at 09:59:07AM +0100, Tomas Hlavaty wrote:
> > : (filter '((This) (= *D (: doc))) (collect 'usr '+Pat *U))
>
> Yes, that's what I wanted. I thought it was possible to avoid
> collecting the whole list constraining the search space before
> collecting the values.
If the list returned by 'collect' is possibly rather long, there are two
better methods:
1. You could use the Pilog functions 'pilog' or 'solve' and 'select'
(pilog
(quote
@U *U
@D *D
(select (@Pat)
((usr +Pat @U) (doc +Pat @D))
(same @U @Pat usr)
(same @D @Pat doc) ) )
(.. do something with the value of '@Pat' ...) )
or
(solve
@U *U
@D *D
(select (@Pat)
((usr +Pat @U) (doc +Pat @D))
(same @U @Pat usr)
(same @D @Pat doc) ) )
-> returns a list
'select' is more efficient than a 'collect' in combination with
'filter', as it traverses the search trees more intelligently.
2. The most efficient way is to use an '+Aux' key. This generates a
combined key in addition to the two indexes for 'usr' and 'doc'.
(class +Pat +Entity)
(rel doc (+Ref +Link) NIL (+Doc))
(rel usr (+Aux +Ref +Link) (doc) NIL (+Usr))
This will cause the 'usr' index to hold combinations of 'usr' and 'doc'.
You can then find all matching hits directly with
: (collect 'usr '+Pat (list *U *D))
but also still use the "normal" way
: (collect 'usr '+Pat *U)
Cheers,
- Alex
--
UNSUBSCRIBE: mailto:picol...@software-lab.de?subject=unsubscribe
