Re: Protect syscache from bloating with negative cache entries

On Thu, Feb 21, 2019 at 1:38 AM Tsunakawa, Takayuki
<tsunakawa(dot)takay(at)jp(dot)fujitsu(dot)com> wrote:
> Why don't we consider this just like the database cache and other DBMS's dictionary caches? That is,
>
> * If you want to avoid infinite memory bloat, set the upper limit on size.
>
> * To find a better limit, check the hit ratio with the statistics view (based on Horiguchi-san's original 0004 patch, although that seems modification anyway)
>
> Why do people try to get away from a familiar idea... Am I missing something?

I don't understand the idea that we would add something to PostgreSQL
without proving that it has value. Sure, other systems have somewhat
similar systems, and they have knobs to tune them. But, first, we
don't know that those other systems made all the right decisions, and
second, even they are, that doesn't mean that we'll derive similar
benefits in a system with a completely different code base and many
other internal differences.

You need to demonstrate that each and every GUC you propose to add has
a real, measurable benefit in some plausible scenario. You can't just
argue that other people have something kinda like this so we should
have it too. Or, well, you can argue that, but if you do, then -1
from me.

--
Robert Haas
EnterpriseDB: http://www.enterprisedb.com
The Enterprise PostgreSQL Company