I wrote: > Simon Riggs <si...@2ndquadrant.com> writes: >> Avoid marking buffer dirty when VACUUM has no work to do. >> When wal_level = 'hot_standby' we touched the last page of the >> relation during a VACUUM, even if nothing else had happened. >> That would alter the LSN of the last block and set the mtime >> of the relation file unnecessarily. Noted by Thom Brown.
> This doesn't look right to me --- you have not accounted for the > possibility that btpo_cycleid or BTP_HAS_GARBAGE is changed. > Also, I'm confused about the business of not setting the LSN. Thom > claimed that he was seeing the page not change at all (or at least > md5sum of the file didn't change) despite mtime changing. If we'd > been plastering a new LSN on the page each time, then that should > certainly not have been possible. So I now think maybe we've > mis-analyzed what was happening in his example. > I think this requires more careful analysis. Ping? If you don't respond, I'm going to take it on my own authority to revert this patch, because it's definitely broken as-is, and I don't think the consequences of not updating the page LSN have been thought through either. regards, tom lane -- Sent via pgsql-hackers mailing list (pgsql-hackers@postgresql.org) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-hackers