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

On Mon, Jun 28, 2010 at 08:08:53AM -0700, Mike Berrow 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?.

Here's a PL/pgsql wrapper for it. You could create a similar wrapper
for other commands.

CREATE OR REPLACE FUNCTION xml_is_well_formed(in_putative_xml TEXT)
STRICT /* Leave this line here if you want RETURNS NULL ON NULL INPUT behavior. */
RETURNS BOOLEAN
LANGUAGE plpgsql
AS $$
BEGIN
PERFORM XMLPARSE(DOCUMENT(in_putative_xml));
RETURN true;
EXCEPTION
WHEN invalid_xml_document THEN
RETURN false;
END;
$$;

While tracking this down, I didn't see a way to get SQLSTATE or the
corresponding condition name via psql. Is this an oversight? A bug,
perhaps?

Cheers,
David.
--
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