Re: [BUG] non archived WAL removed during production crash recovery

On Mon, 20 Apr 2020 16:34:44 +0900
Michael Paquier <michael@paquier.xyz> wrote:
[...]
> > By the way I noticed that RecoveryState is exactly a subset of
> > DBState.  And changes of SharedRecoveryState happens side-by-side with
> > ControlFileData->state in most places.  Coundn't we just usee
> > ControlFile->state instead of SharedRecoveryState?
>
> I actually found confusing to use the same thing, because then the
> reader would thing that SharedRecoveryState could be set to more
> values but we don't want that.

I thought about this while studying various possible fix.

https://www.postgresql.org/message-id/flat/20200401181735.11100908%40firost#6192afba4e4549b8d9bac03168bad46b

The problem is that we would have to read the controldata file each time we
wonder if a segment should be archived/removed. Moreover, the controldata
file might not be in sync quickly enough with the real state for some other
code path or futur needs.

[...]
> Attached is an updated patch, where I tweaked more comments.
>
> Jehan-Guillaume, who is your colleague who found originally about this
> problem?  We should credit him in the commit message.

Indeed, Benoît Lobréau reported this behavior to me.

Regards,