Exist: [BUG] string-join doesn't honour order

[lguariento]

The string-join function does not honour the order of the nodes passed to it. It always returns the nodes in the order they appear in the document.

This code in eXide:

let $index := 
<root>
    <forename>Thomas</forename>
    <surname>Pennant</surname>
</root>

let $person := string-join($index/(surname | forename), ' ')

return $person

Will always return 'Thomas Pennant', even though (surname | forename) above might make one think that it should return Pennant Thomas.

eXist-db 5.2
openjdk 13.0.2 2020-01-14
centOS 7

[dizzzz]

please could you (try to) strip down the query a bit? e.g. is the predicate [@xml:id eq '1'] important or not? Is there a difference with a dynamically generated document and a in-database stored document?

[lguariento]

I've updated my post. I wouldn't know how to strip it down further!

There's no difference between dynamically generated documents and in-database stored document.

[dizzzz]

For xquery related questions I'd recommend to check with Saxon first; here also Thomas Pennan is returned, so we need to study the meaning of | first; it is the union set operator (see https://www.w3schools.com/xml/xpath_operators.asp) so whatever comes first is matched. That is what you see....

[joewiz]

In (surname | forename), the | is an OR operator. Thus, the expression will always return matching results—all surname OR forename elements—in document order. If you want to select nodes in a particular order, use , instead—constructing a new sequence of all surname elements, then all forename elements:

xquery version "3.1";

let $index := 
<root>
    <forename>Thomas</forename>
    <surname>Pennant</surname>
</root>

let $person := string-join($index/(surname, forename), ' ')

return $person

[lguariento]

This is not a bug then, closing.