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BUG #5004: pg_freespacemap make a SegFault

From: "Sebastien Lardiere" <slardiere(at)hi-media(dot)com>
To: pgsql-bugs(at)postgresql(dot)org
Subject: BUG #5004: pg_freespacemap make a SegFault
Date: 2009-08-21 16:26:11
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Lists: pgsql-bugs
The following bug has been logged online:

Bug reference:      5004
Logged by:          Sebastien Lardiere
Email address:      slardiere(at)hi-media(dot)com
PostgreSQL version: 8.3.7
Operating system:   Debian Etch
Description:        pg_freespacemap make a SegFault

I've got a crash with a cluster. Nothing found in the logfile, but a message
about a Segfault, so I get a coredump and here is the backtrace : 

Core was generated by `postgres: postgres postgres [local] SELECT           
Program terminated with signal 11, Segmentation fault.
#0  pg_freespacemap_pages (fcinfo=0x7fff4a9bc250) at pg_freespacemap.c:162
fctx->record[i].reltablespace = fsmrel->key.spcNode;
(gdb) bt
#0  pg_freespacemap_pages (fcinfo=0x7fff4a9bc250) at pg_freespacemap.c:162
#1  0x0000000000526781 in ExecMakeTableFunctionResult (funcexpr=0x29c2408,
econtext=0x29c1b70, expectedDesc=0x29c1ed0, returnDesc=0x7fff4a9bc6d0) at
#2  0x00000000005330d2 in FunctionNext (node=0x29bf620) at
#3  0x000000000052881c in ExecScan (node=0x7fc03f6c5370, accessMtd=0x533030
<FunctionNext>) at execScan.c:68
#4  0x0000000000521f6d in ExecProcNode (node=0x29bf620) at
#5  0x000000000052ca40 in ExecAgg (node=0x29c17f0) at nodeAgg.c:874
#6  0x0000000000521fed in ExecProcNode (node=0x29c17f0) at
#7  0x0000000000520ffd in ExecutorRun (queryDesc=<value optimized out>,
direction=ForwardScanDirection, count=0) at execMain.c:1335
#8  0x00000000005ba0d6 in PortalRunSelect (portal=0x29b47a0, forward=<value
optimized out>, count=0, dest=0x29af198) at pquery.c:943
#9  0x00000000005bb159 in PortalRun (portal=0x29b47a0,
count=9223372036854775807, isTopLevel=1 '\001', dest=0x29af198,
altdest=0x29af198, completionTag=0x7fff4a9bcf40 "") at pquery.c:769
#10 0x00000000005b6d2d in exec_simple_query (query_string=0x2969070 "select
count(*) as pages from pg_freespacemap_pages ") at postgres.c:1004
#11 0x00000000005b8071 in PostgresMain (argc=4, argv=<value optimized out>,
username=0x28bf4b0 "postgres") at postgres.c:3631
#12 0x000000000058ca1b in ServerLoop () at postmaster.c:3207
#13 0x000000000058d73e in PostmasterMain (argc=5, argv=0x28ba310) at
#14 0x0000000000544c15 in main (argc=5, argv=<value optimized out>) at

We can see the use of contrib/pg_freespacemap. A munin plugin sent this
query "select count(*) as pages from pg_freespacemap_pages " every 5 minutes
( since 1 year, now ) and we obtain graph.

I notice that the graph says that our freespacemap is empty ( a few thousand
of pages ) since our first crash. And sometime, the number of pages
increase, and we've got a crash. 

If you want more detail, ask me ... 


PS : Sorry for my poor english


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Subject: Re: 8.4.0 data loss / HOT-related bug
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