Re: Another possible corruption bug in 9.3.2 or possibly a known MultiXact problem? - Mailing list pgsql-hackers

Here's a reformatted copy.  I think this is the same bug as Peter G.
reported in 
http://www.postgresql.org/message-id/CAM3SWZTMQiCi5PV5OWHb+bYkUcnCk=O67w0cSswPvV7XfUcU5g@mail.gmail.com

I have a hunch that this is related to the heap_lock_updated business.
I haven't investigated yet.


Greg Stark wrote:
> I have a database where a a couple rows don't appear in index scans
> but do appear in sequential scans. It looks like the same problem as
> Peter reported but this is a different database. I've extracted all
> the xlogdump records and below are the ones I think are relevant. You
> can see that lp 2 gets a few HOT updates and concurrently has someone
> create a MultiXact NO KEY UPDATE lock while one of those HOT updates
> is pending but not committed. The net result seems to be that the ctid
> update chain got broken. The index of course points to the head of the
> HOT chain so it doesn't find the live tail whereas the sequential scan
> picks it up.
> 
> I don't see any evidence of MultiXactId wraparound, the members run to
> 001F and the offsets run to 000B. This is on a standby that's been
> activated but afaik that shouldn't change these files any more right?
> 
> rmgr: Heap        len (rec/tot):    235/   267, tx:    5943845, lsn: FD/2F0A3640, prev FD/2F0A3600, bkp: 0000, desc:
insert:rel 1663/16385/212653; tid 13065/2
 
> rmgr: Transaction len (rec/tot):     12/    44, tx:    5943845, lsn: FD/2F0A8178, prev FD/2F0A8148, bkp: 0000, desc:
commit:2014-02-19 20:41:23.698513 UTC
 
> rmgr: Heap        len (rec/tot):     25/    57, tx:    5943847, lsn: FD/2F0AA440, prev FD/2F0AA3F8, bkp: 0000, desc:
lock5943847: rel 1663/16385/212653; tid 13065/2 LOCK_ONLY KEYSHR_LOCK
 
> rmgr: Transaction len (rec/tot):     12/    44, tx:    5943847, lsn: FD/2F0AA480, prev FD/2F0AA440, bkp: 0000, desc:
commit:2014-02-19 20:41:23.713969 UTC
 
> rmgr: Heap        len (rec/tot):    291/   323, tx:    5943849, lsn: FD/2F0ADFC0, prev FD/2F0ADF90, bkp: 0000, desc:
hot_update:rel 1663/16385/212653; tid 13065/2 xmax 5943849 ; new tid 13065/3 xmax 0
 
> rmgr: Heap2       len (rec/tot):     25/    57, tx:    5943851, lsn: FD/2F0AE450, prev FD/2F0AE408, bkp: 0000, desc:
lockupdated: xmax 5943851 msk 000a; rel 1663/16385/212653; tid 13065/3
 
> rmgr: MultiXact   len (rec/tot):     28/    60, tx:    5943851, lsn: FD/2F0AE490, prev FD/2F0AE450, bkp: 0000, desc:
createmxid 728896 offset 1632045 nmembers 2: 5943849 (nokeyupd) 5943851 (keysh)
 
> rmgr: Heap        len (rec/tot):     25/    57, tx:    5943851, lsn: FD/2F0AE4D0, prev FD/2F0AE490, bkp: 0000, desc:
lock728896: rel 1663/16385/212653; tid 13065/2 IS_MULTI EXCL_LOCK
 
> rmgr: Transaction len (rec/tot):     12/    44, tx:    5943849, lsn: FD/2F0AE510, prev FD/2F0AE4D0, bkp: 0000, desc:
commit:2014-02-19 20:41:23.744989 UTC
 
> rmgr: Transaction len (rec/tot):     12/    44, tx:    5943851, lsn: FD/2F0AE570, prev FD/2F0AE540, bkp: 0000, desc:
commit:2014-02-19 20:41:23.746820 UTC
 
> rmgr: Heap        len (rec/tot):    306/   338, tx:    5943879, lsn: FD/2F103788, prev FD/2F103758, bkp: 0000, desc:
hot_update:rel 1663/16385/212653; tid 13065/3 xmax 5943879 ; new tid 13065/4 xmax 0
 
> rmgr: Transaction len (rec/tot):     12/    44, tx:    5943879, lsn: FD/2F1038E0, prev FD/2F103788, bkp: 0000, desc:
commit:2014-02-19 20:41:24.580827 UTC
 
> rmgr: Heap        len (rec/tot):    306/   338, tx:    5943880, lsn: FD/2F103910, prev FD/2F1038E0, bkp: 0000, desc:
hot_update:rel 1663/16385/212653; tid 13065/4 xmax 5943880 ; new tid 13065/7 xmax 0
 
> rmgr: Transaction len (rec/tot):     12/    44, tx:    5943880, lsn: FD/2F106070, prev FD/2F106030, bkp: 0000, desc:
commit:2014-02-19 20:41:24.617048 UTC
 
> 
> 
>  lp | lp_off | lp_flags | lp_len | t_xmin  | t_xmax  | t_field3 |   t_ctid   | t_infomask2 | t_infomask | t_hoff |
> ----+--------+----------+--------+---------+---------+----------+------------+-------------+------------+--------+-
>   2 |   3424 |        1 |    232 | 5943845 |  728896 |        0 | (13065,2)  |          32 |       4419 |     32 |
>   3 |   3152 |        1 |    272 | 5943849 | 5943879 |        0 | (13065,4)  |       49184 |       9475 |     32 |
>   4 |   2864 |        1 |    287 | 5943879 | 5943880 |        0 | (13065,7)  |       49184 |       9475 |     32 |
>   7 |   2576 |        1 |    287 | 5943880 |       0 |        0 | (13065,7)  |       32800 |      10499 |     32 |
> 
> 
> -- 
> greg
> 
> 
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Álvaro Herrera                http://www.2ndQuadrant.com/
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