BUG #4922: Segmentation fault on high-loaded server (+coredump backtrace)

The following bug has been logged online:

Bug reference:      4922
Logged by:          Sergey Konoplev
Email address:      gray.ru@gmail.com
PostgreSQL version: 8.3.5
Operating system:   CentOS 5.2 x86-64
Description:        Segmentation fault on high-loaded server (+coredump
backtrace)
Details:

Hello, community.

We faced this segfault few times during the last couple of days. This days
our server was extremly loaded. Before and after this period when LA was
quite normal everything was alright.

I'll do my best answering your questions, so please ask.

Two coredumps backtraces bellow:

Core was generated by `postgres: mirtesen mirtesen [local] UPDATE        '.
Program terminated with signal 11, Segmentation fault.
[New process 8912]
#0  0x000000000065ecf3 in pfree ()
(gdb) bt
#0  0x000000000065ecf3 in pfree ()
#1  0x00002b1a2e1fab2e in ?? () from /usr/lib64/pgsql/pgq_triggers.so
#2  0x0000000000639d41 in ?? ()
#3  0x000000000059840c in ReceiveSharedInvalidMessages ()
#4  0x000000000059a735 in LockRelationOid ()
#5  0x000000000045cf95 in relation_open ()
#6  0x00000000004620bb in index_open ()
#7  0x0000000000461187 in systable_beginscan ()
#8  0x000000000063b496 in ?? ()
#9  0x000000000063da7d in ?? ()
#10 0x000000000063e354 in RelationCacheInvalidateEntry ()
#11 0x0000000000639cfd in ?? ()
#12 0x000000000059840c in ReceiveSharedInvalidMessages ()
#13 0x000000000059a735 in LockRelationOid ()
#14 0x000000000045cf95 in relation_open ()
#15 0x000000000045cfd3 in heap_open ()
#16 0x000000000063b463 in ?? ()
#17 0x000000000063da7d in ?? ()
#18 0x000000000063e354 in RelationCacheInvalidateEntry ()
#19 0x0000000000639cfd in ?? ()
#20 0x000000000059840c in ReceiveSharedInvalidMessages ()
#21 0x000000000059a735 in LockRelationOid ()
#22 0x000000000063a539 in ?? ()
#23 0x000000000063a7e9 in RevalidateCachedPlan ()
#24 0x000000000052f142 in ?? ()
#25 0x000000000052f453 in SPI_execute_plan ()
#26 0x00002b1a2e1fad9b in pgq_find_table_info () from
/usr/lib64/pgsql/pgq_triggers.so
#27 0x00002b1a2e1fb05a in pgq_prepare_event () from
/usr/lib64/pgsql/pgq_triggers.so
#28 0x00002b1a2e1fb68f in pgq_logtriga () from
/usr/lib64/pgsql/pgq_triggers.so
#29 0x00000000004fc35c in ?? ()
#30 0x00000000004fc74e in ?? ()
#31 0x00000000004fc9d7 in AfterTriggerEndQuery ()
#32 0x00000000005a9450 in ?? ()
#33 0x00000000005a9624 in ?? ()
#34 0x00000000005a9e4a in PortalRun ()
#35 0x00000000005a5651 in ?? ()
#36 0x00000000005a6ec8 in PostgresMain ()
#37 0x000000000057d28d in ?? ()
#38 0x000000000057dd69 in PostmasterMain ()
#39 0x000000000053709e in main ()
(gdb)

Core was generated by `postgres: mirtesen mirtesen [local] INSERT        '.

Program terminated with signal 11, Segmentation fault.

[New process 31998]
#0  0x00000038fe878d80 in strlen () from /lib64/libc.so.6
(gdb) bt
#0  0x00000038fe878d80 in strlen () from /lib64/libc.so.6
#1  0x000000000052fefc in appendStringInfoString ()
#2  0x00002af2c47076b1 in pgq_logtriga () from
/usr/lib64/pgsql/pgq_triggers.so
#3  0x00000000004fc35c in ?? ()
#4  0x00000000004fc74e in ?? ()
#5  0x00000000004fc9d7 in AfterTriggerEndQuery ()
#6  0x00000000005a9450 in ?? ()
#7  0x00000000005a9624 in ?? ()
#8  0x00000000005a9829 in ?? ()
#9  0x00000000005a9e68 in PortalRun ()
#10 0x00000000005a5651 in ?? ()
#11 0x00000000005a6ec8 in PostgresMain ()
#12 0x000000000057d28d in ?? ()
#13 0x000000000057dd69 in PostmasterMain ()
#14 0x000000000053709e in main ()
(gdb)