Re: corrupted tuple (header?), pg_filedump output - Mailing list pgsql-hackers

Tom Lane wrote:
> Eric Parusel <lists@globalrelay.net> writes:
> 
>>./pg_filedump -i -f -R 28393 /data1/pgsql/data/base/17760/18004
>>--snip--
>> Item   2 -- Length: 1728  Offset: 6464 (0x1940)  Flags: USED
>>  XMIN: 12  CMIN: 196608  XMAX: 122552335  CMAX|XVAC: 177664675
>>  Block Id: 0  linp Index: 47241   Attributes: 3692   Size: 0
>>  infomask: 0x0900 (XMIN_COMMITTED|XMAX_INVALID)
>>  Error: Computed header length not equal to header size.
>>         Computed <28>  Header: <0>
>>--snip--
> 
> 
> None of those fields seem very sensible.  I suspect what's actually
> corrupt is the ItemId in the page header --- ie, it's pointing at
> something that's not a tuple header.  You might eyeball the ItemId
> array and see if any pattern of corruption is visible.

Ok, the other items in the dump seemed sensible to me.

Is this what you're speaking of?

Block 28393 ********************************************************
<Header> ----- Block Offset: 0x0ddd2000         Offsets: Lower      56 (0x0038) Block: Size 8192  Version    2
 Upper    1064 (0x0428) LSN:  logid    242 recoff 0x9387bd78      Special  8192 (0x2000) Items:    9
FreeSpace: 1008 Length (including item array): 60
 
  0000: f2000000 78bd8793 01000000 38002804  ....x.......8.(.  0010: 00200220 808cb80d 4099800d a485b80d  . .
....@....... 0020: ec847001 28848401 9c984801 b8060000  ..p.(.....H.....  0030: 5c93800a 28040000 00000000
\...(.......

Or, this?:

<Data> ------ Item   1 -- Length: 1756  Offset: 3200 (0x0c80)  Flags: USED Item   2 -- Length: 1728  Offset: 6464
(0x1940) Flags: USED Item   3 -- Length: 1756  Offset: 1444 (0x05a4)  Flags: USED Item   4 -- Length:  184  Offset:
1260(0x04ec)  Flags: USED Item   5 -- Length:  194  Offset: 1064 (0x0428)  Flags: USED Item   6 -- Length:  164
Offset:6300 (0x189c)  Flags: USED Item   7 -- Length:    0  Offset: 1720 (0x06b8)  Flags: 0x00 Item   8 -- Length: 1344
Offset: 4956 (0x135c)  Flags: USED Item   9 -- Length:    0  Offset: 1064 (0x0428)  Flags: 0x00
 


> (Oh btw: are you certain you have the right version of pg_filedump?
> If it's older than your postmaster it might be giving you wrong
> answers.)

Yup, I do believe so, I've got the PGDG 8.0.1 rpms installed and I just 
downloaded the PGDG 8.0.1 contrib srpm, and compiled pg_filedump 
(downloaded from 
http://sources.redhat.com/rhdb/tools/pg_filedump-4.0.tar)...


> If you can do without the whole page, the easiest way is to zero out the
> entire page with 'dd'.  If you just want to kill that one tuple you can
> reset the LP_USED bit in its ItemId.  Either way the postmaster needs to
> be stopped to be sure that it's not got the page buffered while you
> change it.

Ok, how do I go about resetting the LP_USED bit?   I'll make sure the 
postmaster stopped for such an operation...





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Oh crap, I just noticed that there is more than just that item that's 
inconsistent...

Item   6 -- Length:  164  Offset: 6300 (0x189c)  Flags: USED  XMIN: 1852400896  CMIN: 1970348133  XMAX: 543424609
CMAX|XVAC:
 
1869112179  Block Id: 1819244288  linp Index: 29295   Attributes: 2667   Size: 101  infomask: 0x7270 
(HASOID|XMIN_INVALID|MARKED_FOR_UPDATE|UPDATED|MOVED_OFF)  Error: Computed header length not equal to header size.
  Computed <32>  Header: <101>
 

Item   8 -- Length: 1344  Offset: 4956 (0x135c)  Flags: USED  XMIN: 2100285  CMIN: 1644759593  XMAX: 1634148473
CMAX|XVAC:2003137536  Block Id: 2036411953  linp Index: 103   Attributes: 28524   Size: 108  infomask: 0x6162
(HASVARWIDTH|XMIN_COMMITTED|UPDATED|MOVED_OFF) Error: Computed header length not equal to header size.         Computed
<28> Header: <108>
 
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Thanks again,
Eric