Thanks for all the suggestions. >Yeah. In its current shape, it means that only pg_waldump would be >able to know this information. If you make this information part of >xlogdesc.c, any consumer of the WAL record descriptions would be able >to show this information, so it would provide a consistent output for >any kind of tools. I have change the implement, move some code into xlog_desc().
>On top of that, it seems to me that the calculation used in the patch
>is wrong in two aspects at quick glance:
>1) startSegNo and endSegNo point always to two different segments with
>a XLOG_SWITCH record, so you should check that ReadRecPtr is not at a
>segment border instead before extracting SizeOfXLogLongPHD, no?
Yes you are right, and I use 'record->EndRecPtr - 1' instead.
>2) This stuff should also check after the case of a WAL *page* border
>where you'd need to adjust based on SizeOfXLogShortPHD instead.
The 'junk_len -= SizeOfXLogLongPHD' code is considered for when the
remain size of a wal segment can not afford a XLogRecord struct for
XLOG_SWITCH, it needn't care *page* border.
>I'm not sure the exact motive of this proposal, but if we show the
>wasted length in the stats result, I think it should be other than
>existing record types.
Yes agree, and now it looks like below as new patch:
movead@movead-PC:/h2/pg/bin$ ./pg_waldump -p ../walbk/ -s 0/3000000 -e
0/6000000 -z
Type N (%) Record size
(%) FPI size (%) Combined size (%)
---- - --- -----------
--- -------- --- ------------- ---
XLOG 5 ( 31.25) 300
( 0.00) 0 ( 0.00) 300 ( 0.00)
XLOGSwitchJunk 3 ( 18.75) 50330512
(100.00) 0 ( 0.00) 50330512 (100.00)
movead@movead-PC:/h2/pg/bin$ ./pg_waldump -p ../walbk/ -s 0/3000000 -e
0/6000000 --stat=record
XLOG/SWITCH 3 ( 18.75) 72
( 0.00) 0 ( 0.00) 72 ( 0.00)
XLOG/SWITCH_JUNK 3 ( 18.75) 50330512
(100.00) 0 ( 0.00) 50330512 (100.00)
The shortcoming now is I do not know how to handle the 'count' of SWITCH_JUNK
in pg_waldump results. Currently I regard SWITCH_JUNK as one count.
>By the way, I noticed that --stats=record shows two lines for
>Transaction/COMMIT. The cause is that XLogDumpCountRecord assumes the
>all four bits of xl_info is used to identify record id.
Thanks,I didn't notice it before, and your patch added into v3 patch attached.
Regards,
Highgo Software (Canada/China/Pakistan)
URL : www.highgo.ca
EMAIL: mailto:movead(dot)li(at)highgo(dot)ca
fix_waldump_size_for_wal_switch_v3.patch
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