| From: | Thomas Munro <thomas(dot)munro(at)gmail(dot)com> |
|---|---|
| To: | Robert Haas <robertmhaas(at)gmail(dot)com> |
| Cc: | Andres Freund <andres(at)anarazel(dot)de>, Heikki Linnakangas <hlinnaka(at)iki(dot)fi>, pgsql-hackers <pgsql-hackers(at)postgresql(dot)org>, Simon Riggs <simon(dot)riggs(at)enterprisedb(dot)com> |
| Subject: | Re: Make relfile tombstone files conditional on WAL level |
| Date: | 2021-10-05 03:21:39 |
| Message-ID: | CA+hUKG+59sqvrzUx55QLaSGWxmRFpHHUaLMe0giRtzSJBQ383g@mail.gmail.com |
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| Lists: | pgsql-hackers |
On Thu, Sep 30, 2021 at 11:32 PM Thomas Munro <thomas(dot)munro(at)gmail(dot)com> wrote:
> I managed to produce a case where live data is written to an unlinked
> file and lost
I guess this must have been broken since release 9.2 moved checkpoints
out of here[1]. The connection between checkpoints, tombstone files
and file descriptor cache invalidation in auxiliary (non-sinval)
backends was not documented as far as I can see (or at least not
anywhere near the load-bearing parts).
How could it be fixed, simply and backpatchably? If BgSyncBuffer()
did if-FirstCallSinceLastCheckpoint()-then-smgrcloseall() after
locking each individual buffer and before flushing, then I think it
might logically have the correct interlocking against relfilenode
wraparound, but that sounds a tad expensive :-( I guess it could be
made cheaper by using atomics for the checkpoint counter instead of
spinlocks. Better ideas?
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