| From: | "tsunakawa(dot)takay(at)fujitsu(dot)com" <tsunakawa(dot)takay(at)fujitsu(dot)com> |
|---|---|
| To: | 'Simon Riggs' <simon(at)2ndquadrant(dot)com>, Michael Paquier <michael(at)paquier(dot)xyz> |
| Cc: | "pgsql-hackers(at)lists(dot)postgresql(dot)org" <pgsql-hackers(at)lists(dot)postgresql(dot)org> |
| Subject: | RE: Fix of fake unlogged LSN initialization |
| Date: | 2019-10-25 02:07:04 |
| Message-ID: | OSBPR01MB250302CBBABD633900DC1715FE650@OSBPR01MB2503.jpnprd01.prod.outlook.com |
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| Lists: | pgsql-hackers |
From: Simon Riggs <simon(at)2ndquadrant(dot)com>
> From xlogdefs.h added by 9155580:
> /*
> * First LSN to use for "fake" LSNs.
> *
> * Values smaller than this can be used for special per-AM purposes.
> */
> #define FirstNormalUnloggedLSN ((XLogRecPtr) 1000)
Yeah, I had seen it, but I didn't understand what kind of usage is assumed.
> I wonder why is that value 1000, rather than an aligned value or a whole WAL
> page?
I think that's because this fake LSN is not associated with the physical position of WAL records.
Regards
Takayuki Tsunakawa
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