Hi Henrik,
> (class +Proj +Macropisobj)
> (rel id (+Key +Number))
> (rel nm (+Ref +String))
> (rel sDate (+Ref +String))
> (rel eDate (+Ref +String))
>
> (dm getCurrent> (Sdate Edate)
> (filter '((P) (or
> (< Sdate (; P sDate) Edate)
> (< Sdate (; P eDate) Edate)
> (< Sdate (; P sDate) (; P eDate) Edate) ) )
> (collect 'id This) ) )
> ...
> But how would the above problem be solved with Pilog and select if we have
> more than "a couple of hundred objects" in the database?
If you know that the *result* will be within a few hundred hits (not the
total DB size), and the difference between start and end is less than
e.g. 100 days, then you could first restrict the collection a bit
(collect 'sDate '+Proj Sdate (+ Edate 100))
(works of course only for +Date types), and then filter that further.
This is surely the most efficient way for a small set of results.
The same you can do in Pilog with the 'db' predicate for an larger
result set, and if you want to avoid a 'select'
(? @Rng (cons Sdate (+ Edate 100))
(db sDate +Proj @Rng @Proj) )
But 'select' is the most general - and on big data sets perhaps the most
efficient - way. You could try
(?
@Sdate (cons Sdate T) # Range with open end
@Edate (cons Edate NIL) # Reversed range with open start
(select (@Proj)
((sDate +Proj @Sdate) (eDate +Proj @Edate)) # Search two indexes in
parallel
(range @Sdate @Proj sDate) # Check ranges
(range @Edate @Proj eDate) ) ) # Check ranges
I haven't tested this ;)
♪♫ Alex
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