Re: Seg Fault in backend after beginning to use xpath (PG 9.0, FreeBSD 8.1)

On Mon, May 2, 2011 at 10:39 PM, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> alan bryan <alan(dot)bryan(at)gmail(dot)com> writes:
>> Checking out postgres.core and we see:
>
>> (gdb) bt
>> #0  0x00000008f5f19afd in pthread_mutex_lock () from /lib/libthr.so.3
>> #1  0x0000000800d22965 in xmlRMutexLock () from /usr/local/lib/libxml2.so.5
>> #2  0x0000000800d717e1 in xmlDictReference () from /usr/local/lib/libxml2.so.5
>> #3  0x0000000800d74ba5 in xmlSAX2StartDocument ()
>>    from /usr/local/lib/libxml2.so.5
>> #4  0x0000000800ccee5f in xmlParseDocument () from /usr/local/lib/libxml2.so.5
>> #5  0x0000000800ccef85 in xmlDoRead () from /usr/local/lib/libxml2.so.5
>> #6  0x000000000076b58d in xpath ()
>> #7  0x00000000005880e4 in GetAttributeByNum ()
>> #8  0x0000000000588e91 in GetAttributeByName ()
>> #9  0x00000000005850a3 in ExecProject ()
>> #10 0x000000000058c5e4 in ExecScan ()
>> #11 0x0000000000584a2d in ExecProcNode ()
>> #12 0x000000000059bfc8 in ExecLimit ()
>> #13 0x00000000005848f5 in ExecProcNode ()
>> #14 0x0000000000583049 in standard_ExecutorRun ()
>> #15 0x000000000067630d in PostgresMain ()
>> #16 0x0000000000677921 in PortalRun ()
>> #17 0x0000000000672ea4 in pg_parse_and_rewrite ()
>> #18 0x0000000000675354 in PostgresMain ()
>> #19 0x0000000000626afb in ClosePostmasterPorts ()
>> #20 0x0000000000627a8e in PostmasterMain ()
>> #21 0x00000000005bbea7 in main ()
>> (gdb)
>
>> Ideas?  Need more info?
>
> Well, the first thing that you should consider is rebuilding both PG and
> libxml with debug symbols enabled, so you can get a stack trace that's
> worth the electrons it's written on.  That one has enough laughers in
> the PG part to make me not trust the libxml part too much.  That would
> also help you find out what SQL command is being executed, which'd
> possibly lead to being able to create a reproducible test case.
>
>                        regards, tom lane
>

Thanks Tom - I'll see what I can do. We just removed that new code
and did it in our PHP code instead as a workaround. I'll try to spend
some time getting a reproducible test case and come back with a better
trace if possible.

Appreciate the quick response.

--Alan