Re: GIN logging GIN_SEGMENT_UNMODIFIED actions?

On Fri, Aug 26, 2016 at 11:35 PM, Fujii Masao <masao.fujii@gmail.com> wrote:
> On Tue, May 10, 2016 at 9:57 PM, Alexander Korotkov
> <a.korotkov@postgrespro.ru> wrote:
>> Hi!
>>
>> On Mon, May 9, 2016 at 10:46 PM, Andres Freund <andres@anarazel.de> wrote:
>>>
>>> trying to debug something I saw the following in pg_xlogdump output:
>>>
>>> rmgr: Gin         len (rec/tot):      0/   274, tx:          0, lsn:
>>> 1C/DF28AEB0, prev 1C/DF289858, desc: VACUUM_DATA_LEAF_PAGE  3 segments: 5
>>> unknown action 0 ???, blkref #0: rel 1663/16384/16435 blk 310982
>>>
>>> note the "segments: 5 unknown action 0 ???" bit.  That doesn't seem
>>> right, given:
>>> #define GIN_SEGMENT_UNMODIFIED  0               /* no action (not used in
>>> WAL records) */
>>
>>
>> I've checked GIN code.  Have no idea of how such wal record could be
>> generated...
>
> I encountered the same issue when executing the following queries and
> running pg_xlogdump.

ISTM that the cause of this issue is that gin_desc() uses XLogRecGetData() to
extract ginxlogVacuumDataLeafPage data from XLOG_GIN_VACUUM_DATA_LEAF_PAGE
record. Since it's registered by XLogRegisterBufData() in
ginVacuumPostingTreeLeaf(),
XLogRecGetBlockData() should be used, instead. Patch attached. Thought?

BTW, in REDO side, ginRedoVacuumDataLeafPage() uses XLogRecGetBlockData()
to extract ginxlogVacuumDataLeafPage data.

Regards,

--
Fujii Masao