Horton

Re: Regression with large XML data input

Jim Jones <jim.jones@uni-muenster.de>

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From: Jim Jones <jim.jones@uni-muenster.de>
To: Tom Lane <tgl@sss.pgh.pa.us>, Erik Wienhold <ewie@ewie.name>
Cc: Michael Paquier <michael@paquier.xyz>, Robert Treat <rob@xzilla.net>, Postgres hackers <pgsql-hackers@lists.postgresql.org>
Date: 2025-07-29T10:15:28Z
Lists: pgsql-hackers

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On 28.07.25 22:16, Tom Lane wrote:
> Erik's v2 is slightly wrong as to the save-and-restore logic for
> the KeepBlanks setting: we need to restore in the error path too,
> and we'd better mark the save variable volatile since it's modified
> inside the PG_TRY.  I made some other cosmetic changes, mainly to
> avoid calculating "options" when it won't be used.  I tested the
> attached v3 against RHEL8's libxml2-2.9.7, as well as against today's
> libxml2 git master, and it accepts the problematic input on both.

Out of curiosity, what's the reasoning behind keeping node_list instead
of directly using parsed_nodes in the xmlParseBalancedChunkMemory call?

Example:

if (*(utf8string + count))
{
    res_code = xmlParseBalancedChunkMemory(doc, NULL, NULL, 0,
                                           utf8string + count,
                                           parsed_nodes);
    if (res_code != 0 || xmlerrcxt->err_occurred)
    {
        xml_errsave(escontext, xmlerrcxt,
                    ERRCODE_INVALID_XML_CONTENT,
                    "invalid XML content");
        goto fail;
    }
}

I was also wondering if we should add to PG 19 a GUC to enable
XML_MAX_HUGE_LENGTH if so needed. If we go down that route, we'd likely
need to revisit xmlParseBalancedChunkMemory (again!) since it appears to
be hardcoded to XML_MAX_TEXT_LENGTH. Any thoughts?

Best regards, Jim

Commits

  1. Remove unnecessary complication around xmlParseBalancedChunkMemory.

  2. Avoid regression in the size of XML input that we will accept.

  3. Use xmlParseInNodeContext not xmlParseBalancedChunkMemory.

  4. Revert "Add support for parsing of large XML data (>= 10MB)"