Hi Iwan,

IMHO it is more a design issue than a tool issue.

If you need to know exactly where a boolean expression is decided,

You might have to implement a boolean algebra interpreter.

You could even describe your questions in xml format, to be interpreted by a recursive function against your hardware corpus.

That way you could implement rules like :

All ancestors are ‘and’ operators and my current node is ‘false’ => ‘false’

All ancestors are ‘or’ operators’ and my current node is ‘true’ => ‘true’

And detect exactly where your expression is decided.

This make me think of the MarkLogic stored query feature.

Sorry I just thought about that a few minutes,

I hope it helps,

Best regards,

Fabrice

De : BaseX-Talk [mailto:basex-talk-bounces@mailman.uni-konstanz.de] De la part de Iwan Briquemont
Envoyé : mercredi 27 juin 2018 23:04
À : basex-talk@mailman.uni-konstanz.de
Objet : [basex-talk] Tracing query execution

Hello,

I use BaseX mostly for boolean queries, I have a hardware database and I check if specific hardware support features I need.

It works great but when something is not as expected, it's hard to find out the reason.

E.g. given an expression like:

$some-value = $some-list and (custom:predicate() or $x > $y)

I would like to know why it's true or false.

For now I add trace() manually on the subexpressions, rerun, add trace to more specific parts, etc.

Ideally I would want to break down the query execution so it shows the values of subparts of the query to pinpoint why it is false, e.g. have an output like:

$some-value = $some-list and (custom:predicate() or $x > $y) -> false()
$some-value = $some-list -> true()
$some-value -> 1
$some-list -> (1, 2, ..., 10)
custom:predicate() or $x > $y -> false()
custom:predicate() -> false()
... # It should also go inside the function
$x > $y -> false()
$x -> 10
$y -> 11
 

Any ideas how it could be achieved?

Looking at the code, maybe a debug() (like iter() or item()) method could be added to Expr objects which would trace the expression query, file, line and the result of the expression (or probably the first x characters of the result to avoid huge output)? With an xquery function which would trigger it.

I also thought of modifying the query programmatically to add trace() calls but that seems overly complicated.

Best regards,

Iwan