Re: Another possible corruption bug in 9.3.2 or possibly a known MultiXact problem?

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: lock 5943847: 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: lock updated: 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: create mxid 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: lock 728896: 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
>
>
> --
> Sent via pgsql-hackers mailing list (pgsql-hackers(at)postgresql(dot)org)
> To make changes to your subscription:
> http://www.postgresql.org/mailpref/pgsql-hackers

--
Álvaro Herrera http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Training & Services