Re: Regression with large XML data input

On Wed, Jul 23, 2025 at 11:28:38PM -0400, Tom Lane wrote:
> Michael Paquier <michael@paquier.xyz> writes:
>> Switching back to the previous code, where we rely on
>> xmlParseBalancedChunkMemory() fixes the issue.
> 
> Yeah, just reverting these commits might be an acceptable answer,
> since the main point was to work around a bleeding-edge bug:

Still it is not possible to do exactly that on all the branches
because of the business with XMLSERIALIZE that requires some options
for xmlParseInNodeContext(), is it?

>>> * Early 2.13.x releases of libxml2 contain a bug that causes
>>> xmlParseBalancedChunkMemory to return the wrong status value in some
>>> cases.  This breaks our regression tests.  While that bug is now fixed
>>> upstream and will probably never be seen in any production-oriented
>>> distro, it is currently a problem on some more-bleeding-edge-friendly
>>> platforms.
> 
> Presumably that problem is now gone, a year later.  The other point
> about

I would probably agree that it does not seem worth caring for this
range in the early 2.13 series.  I didn't mention it upthread but all
my tests were with debian GID's libxml2 which seems to be a 2.12.7
flavor with some 2.9.14 pieces, based on what apt is telling me.  I
did not test with a different version from upstream, but I'm pretty
sure that's the same story.

>>> * xmlParseBalancedChunkMemory is considered to depend on libxml2's
>>> semi-deprecated SAX1 APIs, and will go away when and if they do.
> 
> is still hypothetical I think.  But we might want to keep this bit:

Worth mentioning upstream 4f329dc52490, I guess, added to the 2.14
branch:
parser: Implement xmlCtxtParseContent

This implements xmlCtxtParseContent, a better alternative to
xmlParseInNodeContext or xmlParseBalancedChunkMemory. It accepts a
parser context and a parser input, making it a lot more versatile.

With all our stable branches, I am not sure if this should be
considered, but that seems worth keeping in mind.

>>> While here, avoid allocating an xmlParserCtxt in DOCUMENT parse mode,
>>> since that code path is not going to use it.

Are you planning to look at that for the next minor release?  It would
take me a couple of hours to dig into all that, and I am sure that I
am going to need your stamp or Erik's to avoid doing a stupid thing.
--
Michael