From: | Alvaro Herrera <alvherre(at)commandprompt(dot)com> |
---|---|
To: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
Cc: | Sokolov Yura <funny(dot)falcon(at)gmail(dot)com>, pgsql-bugs(at)postgresql(dot)org, Peter Eisentraut <peter_e(at)gmx(dot)net>, Patches <pgsql-patches(at)postgresql(dot)org> |
Subject: | Re: BUG #3860: xpath crashes backend when is querying xmlagg result |
Date: | 2008-01-10 21:16:40 |
Message-ID: | 20080110211640.GU6465@alvh.no-ip.org |
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Lists: | pgsql-bugs pgsql-patches |
Tom Lane escribió:
> Alvaro Herrera <alvherre(at)commandprompt(dot)com> writes:
> > Perhaps a better idea is to create a separate LibxmlContext memcxt,
> > child of QueryContext, and have xml_palloc etc always use that. That
> > way it won't be reset between calls. It probably also means we could
> > wire xml reset to transaction abort, making it a bit simpler.
>
> Might as well go back to letting it use malloc :-(.
>
> I actually don't see a problem with letting it use malloc for stuff that
> it is going to manage for itself. I guess the problem comes with
> transient return values of libxml functions; we'd want to explicitly
> move those into palloc-based storage and then free() them.
>
> This looks like a rather large rewrite though. Peter, have you any
> better ideas?
OK, after a lot of research I think the best way to deal with this is
what I suggest above. With the attached patch, I cannot cause the
system to crash with any of the given examples.
Furthermore this may help clean up the PG_TRY blocks that are currently
sprinkled through the xml.c code.
Handling of subtransactions is no good at this point, but I think that
could easily be improved.
--
Alvaro Herrera http://www.CommandPrompt.com/
PostgreSQL Replication, Consulting, Custom Development, 24x7 support
Attachment | Content-Type | Size |
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xml-2.patch | text/x-diff | 5.9 KB |
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