Dear Johannes,
Thanks for the reproducible test case. The bug (a too eager merge of combined range expressions) was fixed and a new snapshot is available [1,2].
Cheers Christian
[1] https://github.com/BaseXdb/basex/issues/1744 [2] http://files.basex.org/releases/latest/
On Thu, Oct 24, 2019 at 10:54 AM Johannes Echterhoff echterhoff@interactive-instruments.de wrote:
Hello,
I’m experiencing some strange behavior when executing the following query in the BaseX 9.2.4 GUI (nevermind the awkward query structure – that is just to be able to inspect the results of the individual evaluation steps):
let $t := <x>200.0000</x>
let $num := number($t)
let $gt5000 := $num gt 5000
let $ltMinus5000 := $num lt -5000
return $gt5000 or $ltMinus5000
The result is true, although it should be false.
The compilation and optimization logs for this query in the GUI tell us the following:
Compiling:
rewrite > comparison to range comparison: ($num_1 > 5000) -> ($num_1 >= 5000.000000000001)
rewrite 'gt' comparison to range comparison: ($num_1 gt 5000) -> ($num_1 >= 5000.000000000001)
pre-evaluate unary expression to xs:integer item: -5000
rewrite < comparison to range comparison: ($num_1 < -5000) -> ($num_1 <= -5000.000000000001)
rewrite 'lt' comparison to range comparison: ($num_1 lt -5000) -> ($num_1 <= -5000.000000000001)
inline $gt5000_2
inline $ltMinus5000_3
simplify or: (true())
pre-evaluate or to xs:boolean item: (true()) -> true()
remove unused variable $num_1
remove unused variable $t_0
simplify FLWOR expression: true()
Optimized Query:
true()
When the return statement is changed to “return ($num,$gt5000,$ltMinus5000,$gt5000 or $ltMinus5000)” then the result of the boolean operation (last element of the result sequence) is false, as expected.
The GUI log then is:
Compiling:
rewrite > comparison to range comparison: ($num_1 > 5000) -> ($num_1 >= 5000.000000000001)
rewrite 'gt' comparison to range comparison: ($num_1 gt 5000) -> ($num_1 >= 5000.000000000001)
pre-evaluate unary expression to xs:integer item: -5000
rewrite < comparison to range comparison: ($num_1 < -5000) -> ($num_1 <= -5000.000000000001)
rewrite 'lt' comparison to range comparison: ($num_1 lt -5000) -> ($num_1 <= -5000.000000000001)
Optimized Query:
let $t_0 := element x { ("200.0000") } let $num_1 := number($t_0) let $gt5000_2 := ($num_1 >= 5000.000000000001) let $ltMinus5000_3 := ($num_1 <= -5000.000000000001) return ($num_1, $gt5000_2, $ltMinus5000_3, ($gt5000_2 or $ltMinus5000_3))
Am I missing something, or could this be a bug in BaseX 9.2.4? With BaseX 9.0.2, both queries (with the different return statements) returned the expected value false for the boolean operation.
Best regards,
Johannes