Greetings, * Robert Haas (robertmh...@gmail.com) wrote: > On Fri, Apr 27, 2018 at 11:35 AM, Andrew Gierth > <and...@tao11.riddles.org.uk> wrote: > >>>>>> "Robert" == Robert Haas <robertmh...@gmail.com> writes: > > Robert> One idea that occurred to me is to somehow record -- I guess in > > Robert> pg_class using non-transactional updates -- the last cutoff XID > > Robert> used to vacuum any given table. Then we could just make a rule > > Robert> that you can't vacuum the TOAST table with an XID that's newer > > Robert> than the last one used for the main table. That would preserve > > Robert> the property that you can vacuum the tables separately while > > Robert> avoiding dangling pointers. But that's obviously not > > Robert> back-patchable, > > > > The suggestion made previously (in a historical thread) was to use an > > entry in the reloptions field for this, at least in back branches. It > > would be necessary for vacuum to add the entry initially in a normal > > transactional update, after which it could be updated inplace. > > Yeah, I suppose. Sounds pretty rickety to me, though. Maybe I'm just > a pessimist.
I tend to agree.. However, this isn't something that's been happening a lot, from what I gather, and if we actually add a proper column into pg_class for future versions (not really sure how I feel about if that means "v11" or "v12" right now...) and reloptions for back-branches then perhaps it's not so bad. As far as a metadata page, it'd be pretty overkill, but maybe a fork for it..? I'm trying to think if there might be anything else we'd be able to put into such a fork since adding another inode to every relation that'll only ever likely be 8k definitely wouldn't win us any fans. Not sure, just brainstorming. Thanks! Stephen
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