Horton

Re: possible encoding issues with libxml2 functions

Pavel Stehule <pavel.stehule@gmail.com>

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From: Pavel Stehule <pavel.stehule@gmail.com>
To: Noah Misch <noah@leadboat.com>
Cc: PostgreSQL Hackers <pgsql-hackers@postgresql.org>
Date: 2017-08-21T04:25:29Z
Lists: pgsql-hackers 
>
> xpath-bugfix.patch affected only xml values containing an xml declaration
> with
> "encoding" attribute.  In UTF8 databases, this latest proposal
> (xpath-parsing-error-fix.patch) is equivalent to xpath-bugfix.patch.  In
> non-UTF8 databases, xpath-parsing-error-fix.patch affects all xml values
> containing non-ASCII data.  In a LATIN1 database, the following works today
> but breaks under your latest proposal:
>
>   SELECT xpath('text()', ('<x>' || convert_from('\xc2b0', 'LATIN1') ||
> '</x>')::xml);
>
> It's acceptable to break that, since the documentation explicitly disclaims
> support for it.  xpath-bugfix.patch breaks different use cases, which are
> likewise acceptable to break.  See my 2017-08-08 review for details.
>

The fact so this code is working shows so a universe is pretty dangerous
place :)

Commits

  1. Ignore XML declaration in xpath_internal(), for UTF8 databases.

  2. Add warning that xpath() doesn't work with non-UTF8 data.