Re: BUG #4294: XML support: name() xpath function not working

From: Bruce Momjian <bruce(at)momjian(dot)us>
To: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Cc: Enrico Sirola <enrico(dot)sirola(at)gmail(dot)com>, pgsql-bugs(at)postgresql(dot)org, Peter Eisentraut <peter_e(at)gmx(dot)net>
Subject: Re: BUG #4294: XML support: name() xpath function not working
Date: 2008-08-23 03:22:09
Message-ID: 200808230322.m7N3M9w06962@momjian.us
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Is there any TODO here?

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Tom Lane wrote:
> "Enrico Sirola" <enrico(dot)sirola(at)gmail(dot)com> writes:
> > -- bad
> > select xpath('name(/my:a/*[last()])', test, ARRAY[ARRAY['my',
> > 'http://myns.com/ns']]) from test;
>
> You could barely swat a fly with what I know about XPath ... but I'm
> thinking that the culprit here is the crock at lines 3254-3288 of
> xml.c, which explains itself thus:
>
> /*
> * To handle both documents and fragments, regardless of the fact whether
> * the XML datum has a single root (XML well-formedness), we wrap the XML
> * datum in a dummy element (<x>...</x>) and extend the XPath expression
> * accordingly. To do it, throw away the XML prolog, if any.
> */
>
> This code prefixes the given path expression with "/x", which of course
> is going to break any expression that starts with a function name. It
> would have to stick the /x inside the function argument to have any
> chance of working. In general, I think this has zero chance of working
> without implementing a pretty complete XPath parser. We need to find
> another way.
>
> regards, tom lane
>
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Bruce Momjian <bruce(at)momjian(dot)us> http://momjian.us
EnterpriseDB http://enterprisedb.com

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