[xquery-talk] Update bug?

[Ghislain Fourny]

Hi Leo, Joseph,

Actually, the semantics of the XQuery Update Facility is based on
snapshots, which means that the order of the expressions is irrelevant in
terms of updates. Each expression is evaluated against the original
document, gathering a set of updates known as a PUL, and the updates are
only applied at the very end.

Even with the delete coming first, the insert still should see the
to-be-deleted node. Even if you swap the two expressions, the engine may
still evaluate the second expression first under the hood, or even in
parallel, and you won't see any difference. Commas have a monoid
(concatenation) semantics when used with items, but no elapse-of-time
semantics.

The XQuery Update Facility , like XQuery was very cleanly designed as a
declarative language :-)

I hope it's useful.

Kind regards,
Ghislain


On Tue, Oct 6, 2015 at 6:54 PM, Joseph Bryan <joemfb at gmail.com> wrote:

> Hi Leo,
>
> Try reversing the order of your statements, first inserting the node as a
> child of <b/> before deleting it.
>
> Also, you probably don't want to be using // in your selectors, which
> means the descendant-or-self axis. With that XPath expression, any @att at
> any level of the document would be copied and then deleted. Instead, use
> exact paths with a single /, which is the child axis.
>
> insert node doc("xml.xml")/a/@att into doc("xml.xml")/a/b,
> delete node doc("xml.xml")/a/@att
>
> Thanks.
>
> -jb
>
> On Tue, Oct 6, 2015 at 12:23 PM, Leo Studer <leo.studer at varioweb.ch>
> wrote:
>
>> Hello
>>
>> I am using Oxygen 17.0 with Saxon EE 9.6.0.5 as the xQuery Update
>> processor.
>>
>> I want to move an attribute one level deeper.
>>
>> In the example I want to move att="att” from <a> to <b>
>>
>> <?xml version="1.0" encoding="UTF-8"?>
>> <a att="att">
>>     <b/>
>> </a>
>>
>> Here my code:
>>
>> *delete* *node* *doc*("xml.xml")//*@att*,
>> *insert* *node* *doc*("xml.xml")//*@att* *into **doc*("xml.xml")//*b*
>>
>> Each of these two statements work correctly alone but when I try both
>> together I get java.lang.NullPointerException.
>>
>> Can anyone explain what happens here?
>>
>> Thanks in advance
>> Leo
>>
>>
>>
>>
>>
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>
>
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