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Re: patch: function xmltable

From: Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>
To: Craig Ringer <craig(at)2ndquadrant(dot)com>
Cc: PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: patch: function xmltable
Date: 2016-09-27 05:29:03
Message-ID: CAFj8pRAC=z_qPdA5PHmP_VzsnTiLU2cOyF5_DWcQSjp+cmqryA@mail.gmail.com (view raw, whole thread or download thread mbox)
Thread:
Lists: pgsql-hackers
2016-09-27 5:53 GMT+02:00 Craig Ringer <craig(at)2ndquadrant(dot)com>:

> On 24 September 2016 at 14:01, Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com>
> wrote:
>
> >> Did some docs copy-editing and integrated some examples. Explained how
> >> nested elements work, that multiple top level elements is an error,
> >> etc. Explained the time-of-evaluation stuff. Pointed out that you can
> >> refer to prior output columns in PATH and DEFAULT, since that's weird
> >> and unusual compared to normal SQL. Documented handling of multiple
> >> node matches, including the surprising results of somepath/text() on
> >> <somepath>x<!--blah-->y</somepath>. Documented handling of nested
> >> elements. Documented that xmltable works only on XML documents, not
> >> fragments/forests.
> >
> >
> > I don't understand to this sentence: "It is possible for a PATH
> expression
> > to reference output columns that appear before it in the column-list, so
> > paths may be dynamically constructed based on other parts of the XML
> > document:"
>
> This was based on a misunderstanding of something you said earlier. I
> thought the idea was to allow this to work:
>
> SELECT * FROM xmltable('/x' PASSING
> '<x><elemName>a</elemName><a>value</a></x>' COLUMNS elemName text,
> extractedValue text PATH elemName);
>
> ... but it doesn't:
>
>
> SELECT * FROM xmltable('/x' PASSING
> '<x><elemName>a</elemName><a>value</a></x>' COLUMNS elemName text,
> extractedValue text PATH elemName);
> ERROR:  column "elemname" does not exist
> LINE 1: ...' COLUMNS elemName text, extractedValue text PATH elemName);
>
> ... so please delete that text. I thought I'd tested it but the state
> of my tests dir says I just got distracted by another task at the
> wrong time.
>

deleted

Regards

Pavel

>
> --
>  Craig Ringer                   http://www.2ndQuadrant.com/
>  PostgreSQL Development, 24x7 Support, Training & Services
>

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