Re: Issue: Deprecation of the XML2 module 'xml_is_well_formed' function

On Mon, Jun 28, 2010 at 11:08 AM, Mike Berrow <mberrow@gmail.com> wrote:
> We need to make extensive use of the 'xml_is_well_formed' function provided
> by the XML2 module.
> Yet the documentation says that the xml2 module will be deprecated since
> "XML syntax checking and XPath queries"
> is covered by the XML-related functionality based on the SQL/XML standard in
> the core server from PostgreSQL 8.3 onwards.
> However, the core function XMLPARSE does not provide equivalent
> functionality since when it detects an invalid XML document,
> it throws an error rather than returning a truth value (which is what we
> need and currently have with the 'xml_is_well_formed' function).
> For example:
> select xml_is_well_formed('<br></br2>');
>  xml_is_well_formed
> --------------------
>  f
> (1 row)
> select XMLPARSE( DOCUMENT '<br></br2>' );
> ERROR:  invalid XML document
> DETAIL:  Entity: line 1: parser error : expected '>'
> <br></br2>
>         ^
> Entity: line 1: parser error : Extra content at the end of the document
> <br></br2>
>         ^
> Is there some way to use the new, core XML functionality to simply return a
> truth value
> in the way that we need?.

You could do something like this (untested):

CREATE OR REPLACE FUNCTION my_xml_is_valid ( x TEXT ) RETURNS BOOL AS $$
BEGIN PERFORM XMLPARSE( DOCUMENT x::XML ); RETURN TRUE;
EXCEPTION WHEN OTHERS THEN RETURN FALSE;
END;
$$ LANGUAGE PLPGSQL;

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