From: | Peter Eisentraut <peter_e(at)gmx(dot)net> |
---|---|
To: | Scott Bailey <artacus(at)comcast(dot)net> |
Cc: | hackers <pgsql-hackers(at)postgresql(dot)org> |
Subject: | Re: Proposal: XML helper functions |
Date: | 2010-01-05 21:13:56 |
Message-ID: | 1262726036.6448.3.camel@vanquo.pezone.net |
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Thread: | |
Lists: | pgsql-hackers |
On tis, 2010-01-05 at 11:50 -0800, Scott Bailey wrote:
> > There has been talk about adding something like xpath_string,
> > xpath_number, xpath_boolean for fetching xpath expressions that
> don't
> > return nodesets. I think that would fit your use case.
>
> The first two sound very much like what I'm looking for. I'm unsure
> about the third. Is it's purpose to extract the scalar value of an
> expression and cast to bool as the other two do, or is it to identify
> if the xpath expression returned any nodes like xmlexists?
XPath as a language has four data types: nodeset, string, number,
boolean. So an XPath expression could return any of those types. Then,
I suppose, the xpath_foo() function would evaluate the expression and
return the result as type foo, possibly raising an error if the types
don't match.
Details to be determined.
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