Re: Protect syscache from bloating with negative cache entries

On 2017-12-16 22:25:48 -0500, Robert Haas wrote:
> On Wed, Dec 13, 2017 at 11:20 PM, Kyotaro HORIGUCHI
> <horiguchi.kyotaro@lab.ntt.co.jp> wrote:
> > Thank you very much for the valuable suggestions. I still would
> > like to solve this problem and the
> > a-counter-freely-running-in-minute(or several seconds)-resolution
> > and pruning-too-long-unaccessed-entries-on-resizing seems to me
> > to work enough for at least several known bloat cases. This still
> > has a defect that this is not workable for a very quick
> > bloating. I'll try thinking about the remaining issue.
> 
> I'm not sure we should regard very quick bloating as a problem in need
> of solving.  Doesn't that just mean we need the cache to be bigger, at
> least temporarily?

Leaving that aside, is that actually not at least to a good degree,
solved by that problem? By bumping the generation on hash resize, we
have recency information we can take into account.

Greetings,

Andres Freund