Hi Marco,
> ("a", "b", "c")[trace(1 + random:integer(3))]
The filter expression is defined in such a way that the predicate is
evaluated anew for every item of the sequence. If you want
random:integer(3) to be evaluated only once, you can either bind it to a
variable…
let $r := random:integer(3) + 1
return ("a", "b", "c")]$r]
…or use functions like fn:subsequence:
subsequence(("a", "b", "c"), random:integer(3) + 1, 1)
Hope this helps,
Christian
Marco Lettere <m.lett...@gmail.com> schrieb am Mi., 22. Mai 2024, 15:34:
> Dear all,
>
> I have this strange behavior when running in BaseX 10.4:
>
> ["a","b","c"](1 + random:integer(3))
>
> I got something empty result, sometimes (correctly) one out of the
> three, sometimes two results...
>
> I report the results and the trace in [1] and [2].
>
> What is the reason for this?
>
> Thank you.
>
> Marco.
>
> [1] Two results
> a
> c
>
> Evaluating:
> 1
> 3
> 3
> Compiling:
> - rewrite list to xs:string sequence: ("a", "b", "c")
> - swap operands: (1 + random:integer(3))
> Optimized Query:
> ("a", "b", "c")[trace((random:integer(3) + 1))]
> Query:
> ("a", "b", "c")[trace(1 + random:integer(3))]
> Result:
> - Hit(s): 2 Items
> - Updated: 0 Items
> - Printed: 3 b
> - Read Locking: (none)
> - Write Locking: (none)
> Timing:
> - Parsing: 0.21 ms
> - Compiling: 0.4 ms
> - Optimizing: 0.1 ms
> - Evaluating: 0.57 ms
> - Printing: 0.02 ms
> - Total Time: 1.31 ms
>
>
> [2] Empty result
> ()
>
> Evaluating:
> 3
> 3
> 1
> Compiling:
> - rewrite list to xs:string sequence: ("a", "b", "c")
> - swap operands: (1 + random:integer(3))
> Optimized Query:
> ("a", "b", "c")[trace((random:integer(3) + 1))]
> Query:
> ("a", "b", "c")[trace(1 + random:integer(3))]
> Result:
> - Hit(s): 0 Items
> - Updated: 0 Items
> - Printed: 0 b
> - Read Locking: (none)
> - Write Locking: (none)
> Timing:
> - Parsing: 0.16 ms
> - Compiling: 0.41 ms
> - Optimizing: 0.15 ms
> - Evaluating: 0.56 ms
> - Printing: 0.02 ms
> - Total Time: 1.3 ms
> Query Plan:
> <QueryPlan compiled="true" updating="false">
> <CachedFilter type="xs:string*">
> <StrSeq type="xs:string+" size="3">
> <Str type="xs:string" size="1">a</Str>
> <Str type="xs:string" size="1">b</Str>
> <Str type="xs:string" size="1">c</Str>
> </StrSeq>
> <FnTrace name="trace" type="xs:integer" size="1">
> <Arith op="+" type="xs:integer" size="1">
> <RandomInteger name="random:integer" type="xs:integer" size="1">
> <Int type="xs:integer" size="1">3</Int>
> </RandomInteger>
> <Int type="xs:integer" size="1">1</Int>
> </Arith>
> </FnTrace>
> </CachedFilter>
> </QueryPlan>
>
>
