Re: BUG #17245: Index corruption involving deduplicated entries

On 2021-Oct-29, Kamigishi Rei wrote:

> The weird part about this is that the WAL archive does not seem to contain
> any data for 157 and 158 above (in 1663/19243/274869 blk 17). The last two
> entries are
> 
> rmgr: Btree       len (rec/tot):     53/  4885, tx:    2085600, lsn:
> 2/A0195AE0, prev 2/A01943F0, desc: INSERT_LEAF off 155, blkref #0: rel
> 1663/19243/274869 blk 17 FPW
> rmgr: Btree       len (rec/tot):     72/    72, tx:    2085602, lsn:
> 2/A019DD30, prev 2/A019DCF0, desc: INSERT_LEAF off 156, blkref #0: rel
> 1663/19243/274869 blk 17
> 
> The WAL file in data14/pg_wal does not have anything related to 157 and 158
> for this filenode/blk as well.

Hmm, I don't remember precisely how index tuple removal works, but maybe
these 157 and 158 entries existed previously and were truncated away.
It might be useful to have a look at the page header in the page image
contained in the FPW for 2/A0195AE0.

pg_waldump doesn't do it, but I have this patch sitting around ...
probably outdated, but it may be a useful starting point for somebody.

-- 
Álvaro Herrera              Valdivia, Chile  —  https://www.EnterpriseDB.com/