| From: | Pavel Stehule <pavel(dot)stehule(at)gmail(dot)com> |
|---|---|
| To: | Alvaro Herrera <alvherre(at)2ndquadrant(dot)com> |
| Cc: | Craig Ringer <craig(at)2ndquadrant(dot)com>, PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: patch: function xmltable |
| Date: | 2016-11-24 04:52:46 |
| Message-ID: | CAFj8pRA5vz20Le5EQ-5MGygWs7kh0azTRLt9=rvS8GWMWfw_jA@mail.gmail.com |
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| Lists: | pgsql-hackers |
Hi
2016-11-24 0:13 GMT+01:00 Alvaro Herrera <alvherre(at)2ndquadrant(dot)com>:
> Oh my, I just noticed we have a new xpath preprocessor in this patch
> too. Where did this code come from -- did you write it all from
> scratch?
>
I wrote it from scratch - libxml2 has not any API for iteration over XPath
expression (different than iteration over XPath expression result), and
what I have info, there will not be any new API in libxml2.
There are two purposes:
Safe manipulation with XPath expression prefixes - ANSI SQL design
implicitly expects some prefix, but it can be used manually. The prefix
should not be used twice and in some situations, when it can breaks the
expression.
Second goal is support default namespaces - when we needed parser for first
task, then the enhancing for this task was not too much lines more.
This parser can be used for enhancing current XPath function - default
namespaces are pretty nice, when you have to use namespaces.
>
> --
> Álvaro Herrera https://www.2ndQuadrant.com/
> PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services
>
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