Re: [HACKERS] proposal - Default namespaces for XPath expressions (PostgreSQL 11)

From: Kyotaro HORIGUCHI <horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp>
To: pavel(dot)stehule(at)gmail(dot)com
Cc: 9erthalion6(at)gmail(dot)com, tgl(at)sss(dot)pgh(dot)pa(dot)us, thomas(dot)munro(at)enterprisedb(dot)com, pgsql-hackers(at)postgresql(dot)org
Subject: Re: [HACKERS] proposal - Default namespaces for XPath expressions (PostgreSQL 11)
Date: 2018-11-30 08:26:27
Message-ID: 20181130.172627.173653111.horiguchi.kyotaro@lab.ntt.co.jp
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Hello.

At Fri, 30 Nov 2018 07:48:26 +0100, Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> wrote in <CAFj8pRD7Zg07t4NpZu09T4RgXz0bTvyYg2eMVoH+o_drNoiz6w(at)mail(dot)gmail(dot)com>
> Hi
>
> čt 29. 11. 2018 v 14:44 odesílatel Dmitry Dolgov <9erthalion6(at)gmail(dot)com>
> napsal:
>
> > > On Fri, Sep 21, 2018 at 1:30 PM Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>
> > wrote:
> > >
> > > Thank you for comments
> > >
> > > Attached updated patch
> >
> > Unfortunately, current version of the patch doesn't pass make check,
> > something
> > is missing for xml tests. Could you please rebase it?
> >
> > After that I hope someone from reviewers (Kyotaro?) can probably confirm if
> > it's still in a good shape. For now I'm moving it to the next CF.

Sure. Sorry for coming late. I reconfirmed this.

The most significant change in this version is namespace name
generaton.

- We can remove strlen from mutate_name by mutating the string in
reverse order. We don't need to mutate it in a human-affinity
order. The name would be 1-letter in almost all cases.

Concretely, the order in my mind is the follows:

"" "a" "b" ..."z" "aa" "ba" "ca"... "za" "ab"..

- Might the 'propriety' correctly be 'properties'?

+ /* register namespace if all propriety are available */

- Is the "if" a mistake of "in"?

+ * collect ns names if ResTarget format for possible usage
+ * in getUniqNames function.

- I suppose the following should be like "register default
namespace definition if any".

+ /* get default namespace name when it is required */

Maybe the followings are not new. (Note that I'm not a naitive speaker.)

- I cannot read this. (I might be to blame..)

+ * default namespace for XPath expressions. Because there are not any API
+ * how to transform or access to parsed XPath expression we have to parse
+ * XPath here.

- This might need to explain "by what".

+ * Those functionalities are implemented with a simple XPath parser/
+ * preprocessor. This XPath parser transforms a XPath expression to another
+ * XPath expression that can be used by libxml2 XPath evaluation. It doesn't
+ * replace libxml2 XPath parser or libxml2 XPath expression evaluation.

- "add" -> "adds", "def_namespace_name" seems to need to be
replaced with something else.

+ * This transformation add def_namespace_name to any unqualified node name
+ * or attribute name of xpath expression.

(Sorry, I'll look further later.)

regards.

--
Kyotaro Horiguchi
NTT Open Source Software Center

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