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Re: xpath not a good replacement for xpath_string

From: Mike Rylander <mrylander(at)gmail(dot)com>
To: pgsql(at)mohawksoft(dot)com
Cc: Kevin Grittner <Kevin(dot)Grittner(at)wicourts(dot)gov>, Andrew Dunstan <andrew(at)dunslane(dot)net>, PostgreSQL <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: xpath not a good replacement for xpath_string
Date: 2009-07-28 23:20:20
Message-ID: b918cf3d0907281620h6fc6d068uc036fbc2b6488fa5@mail.gmail.com (view raw or flat)
Thread:
Lists: pgsql-hackers
On Tuesday, July 28, 2009,  <pgsql(at)mohawksoft(dot)com> wrote:
>> Andrew Dunstan <andrew(at)dunslane(dot)net> wrote:
>>
>>> in fact the desired functionality is present [...] You just need to
>>> use the text() function to get the contents of the node, and an
>>> array subscript to pull it out of the result array.
>>
>> I just took a quick look, and that didn't jump out at me from the
>> documentation.  Perhaps there should be an example or two of how to
>> get the equivalent functionality through the newer standard API, for
>> those looking to migrate?
>>
>> Would it make sense to supply convenience SQL functions which map
>> some of the old API to the new?
>
> The thing that perplexed me was that it was not obvious from the docs how,
> exactly, to get the functionality that was simple and straight forward in
> XML2.
>
> Another thing that is troubling is that more exotic types do not seem to
> be supported at all. For instance, in my example I used uuid, and if one
> substitutes "uuid()" for "text()" that doesn't work.
>

text() is an XPath function used to extract the text content of a
node, in this case the uuid element.

> The API is less intuitive than the previous incarnation and is, indeed,
> more difficult to use.

It may be easier to use for those not familiar with more advanced
XPath, but it also has non-standard default actions.  That being said,
I'd love to see wrapper functions that provide the older api but
leverage the core code.

--miker


-- 
Mike Rylander
 | VP, Research and Design
 | Equinox Software, Inc. / The Evergreen Experts
 | phone:  1-877-OPEN-ILS (673-6457)
 | email:  miker(at)esilibrary(dot)com
 | web:  http://www.esilibrary.com

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