Re: PostgreSQL vs SQL/XML Standards

From: Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>
To: Markus Winand <markus(dot)winand(at)winand(dot)at>
Cc: Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>, Chapman Flack <chap(at)anastigmatix(dot)net>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: PostgreSQL vs SQL/XML Standards
Date: 2018-11-09 04:07:52
Message-ID: CAFj8pRC_bi4uzE3Z-XXuGnLFPP-7cZ-zr2JhGauWm3E8K2MqEg@mail.gmail.com
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čt 8. 11. 2018 v 15:18 odesílatel Markus Winand <markus(dot)winand(at)winand(dot)at>
napsal:

>
> > On 2018-11-6, at 15:23 , Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> wrote:
> >
> >
> >
> > po 29. 10. 2018 v 11:45 odesílatel Pavel Stehule <
> pavel(dot)stehule(at)gmail(dot)com> napsal:
> >
> >
> > po 29. 10. 2018 v 10:11 odesílatel Pavel Stehule <
> pavel(dot)stehule(at)gmail(dot)com> napsal:
> > Hi
> >
> > čt 25. 10. 2018 v 21:47 odesílatel Alvaro Herrera <
> alvherre(at)2ndquadrant(dot)com> napsal:
> > On 2018-Oct-25, Pavel Stehule wrote:
> >
> > > I am thinking so I can fix some issues related to XMLTABLE. Please,
> send me
> > > more examples and test cases.
> >
> > Please see Markus Winand's patch that I referenced upthread.
> >
> > here is a fix of some XMLTABLE mentioned issues.
> >
> > this update allows cast boolean to numeric types from XPath expressions
> >
> > Attached patch solves some cast issues mentioned by Chap. It solves
> issue reported by Markus. I didn't use Markus's code, but it was
> inspiration for me. I found native solution from libxml2.
> >
> > Regards
> >
> > Pavel
>
> Better than my patch.
>
> But I think the chunk in xml_xmlnodetoxmltype of my patch is still needed
> — in one way or the other (see below).
>
> # select * from xmltable('*' PASSING '<e>pre<!--c1--><?pi
> arg?><![CDATA[&ent1]]><n2>&amp;deep</n2>post</e>' COLUMNS x XML PATH
> 'node()');
> x
> -----------------------------------------
> prec1arg&amp;ent1<n2>&amp;deep</n2>post
> (1 row)
>
> Output is not the original XML.
>
> I dug a little further and found another case that doesn’t looks right
> even with my change to xml_xmlnodetoxmltype applied:
>
> # select * from xmltable('*' PASSING '<e>pre<!--c1--><?pi
> arg?><![CDATA[&ent1]]><n2>&amp;deep</n2>post</e>' COLUMNS x XML PATH '/');
> x
> ---------------------------
> pre&amp;ent1&amp;deeppost
> (1 row)
>
> Oracle gives in both cases XML.
>
> To fix that I included XML_DOCUMENT_NODE in the list of nodes that use
> xmlNodeDump. Now I wonder if that logic should be reversed to use the
> xmlXPathCastNodeToString branch in a few selected cases but default to the
> branch xmlNodeDump for all other cases?
>
> I guess those few cases might be XML_ATTRIBUTE_NODE and XML_TEXT_NODE.
> Regression tests are happy with that approach but I don’t think that proves
> a lot.
>
> -markus
>
> diff --git a/src/backend/utils/adt/xml.c b/src/backend/utils/adt/xml.c
> index 37d85f7..7c1f884 100644
> --- a/src/backend/utils/adt/xml.c
> +++ b/src/backend/utils/adt/xml.c
> @@ -3682,7 +3682,7 @@ xml_xmlnodetoxmltype(xmlNodePtr cur,
> PgXmlErrorContext *xmlerrcxt)
> {
> xmltype *result;
>
> - if (cur->type == XML_ELEMENT_NODE)
> + if (cur->type != XML_ATTRIBUTE_NODE && cur->type != XML_TEXT_NODE)
> {
> xmlBufferPtr buf;
> xmlNodePtr cur_copy;
>
>
I used your patch and append regress tests. I checked the result against
Oracle.

Regards

Pavel

Attachment Content-Type Size
xmltable-xpath-result-processing-bugfix-2.patch text/x-patch 8.2 KB

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