Re: xpath processing brain dead - Mailing list pgsql-hackers

From Andrew Dunstan
Subject Re: xpath processing brain dead
Date
Msg-id 49C3BCAD.60308@dunslane.net
Whole thread Raw
In response to Re: xpath processing brain dead  (Andrew Dunstan <andrew@dunslane.net>)
Responses Re: xpath processing brain dead  (James Pye <lists@jwp.name>)
List pgsql-hackers

Andrew Dunstan wrote:
>
>
> Hannu Krosing wrote:
>> Is it just that in you _can't_ use Xpath on fragments, and you _need_ to
>> pass full documents to Xpath ?
>> At least this is my reading of Xpath standard.
>>
>>   
>
> I think that's possibly overstating it., unless I have missed 
> something (W3 standards are sometimes not much more clear than the SQL 
> standards ;-( )
>
> For instance, there's this, that implies at least that the tree might 
> not be a document:
>
>    A "/" at the beginning of a path expression is an abbreviation for
>    the initial step fn:root(self::node()) treat as document-node()/
>    (however, if the "/" is the entire path expression, the trailing "/"
>    is omitted from the expansion.) The effect of this initial step is
>    to begin the path at the root node of the tree that contains the
>    context node. If the context item is not a node, a type error is
>    raised [err:XPTY0020]. At evaluation time, if the root node above
>    the context node is not a document node, a dynamic error is raised
>    [err:XPDY0050].
>
> The problem is that we certainly do have to provide a context node 
> (the standard is clear about that), and unless we want to convert a 
> non-document to a node-set as James suggested and then apply the xpath 
> expression to each node in the node-set, we have no way of sanely 
> specifying the context node.
>

No-one has come up with an answer to this, so I propose to remove the 
hackery. That leaves the question of what to do when the xml is not a 
well formed document ... raise an error?

cheers

andrew


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