Re: Fix of fake unlogged LSN initialization

On Fri, Oct 25, 2019 at 02:07:04AM +0000, tsunakawa(dot)takay(at)fujitsu(dot)com wrote:
> 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.

There is an explanation in the commit message of 9155580: that's to
make an interlocking logic in GiST able to work where a valid LSN
needs to be used. So a magic value was just wanted.

Your patch looks fine to me by the way after a second look, so I think
that we had better commit it and back-patch sooner than later. If
there are any objections or more comments, please feel free..
--
Michael