| From: | Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> |
|---|---|
| To: | Michael Paquier <michael(dot)paquier(at)gmail(dot)com> |
| Cc: | Robert Haas <robertmhaas(at)gmail(dot)com>, Kyotaro HORIGUCHI <horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp>, David Steele <david(at)pgmasters(dot)net>, Jim Nasby <Jim(dot)Nasby(at)bluetreble(dot)com>, Craig Ringer <craig(at)2ndquadrant(dot)com>, PostgreSQL mailing lists <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Protect syscache from bloating with negative cache entries |
| Date: | 2017-11-30 04:17:23 |
| Message-ID: | 84820.1512015443@sss.pgh.pa.us |
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| Lists: | pgsql-hackers |
Michael Paquier <michael(dot)paquier(at)gmail(dot)com> writes:
> On Thu, Nov 30, 2017 at 12:32 PM, Robert Haas <robertmhaas(at)gmail(dot)com> wrote:
>> I think we have to mark this as returned with feedback or rejected for
>> the reasons mentioned here:
>> http://postgr.es/m/CA+TgmoZjn28uYJRQ2K+5idhYxWBDER68sctoc2p_nW7h7JbhYw@mail.gmail.com
> Good point. I forgot this bit. Thanks for mentioning it I am switching
> the patch as returned with feedback.
We had a bug report just today that seemed to me to trace to relcache
bloat:
https://www.postgresql.org/message-id/flat/20171129100649.1473.73990%40wrigleys.postgresql.org
ISTM that there's definitely work to be done here, but as I said upthread,
I think we need a more holistic approach than just focusing on negative
catcache entries, or even just catcache entries.
The thing that makes me uncomfortable about this is that we used to have a
catcache size limitation mechanism, and ripped it out because it had too
much overhead (see commit 8b9bc234a). I'm not sure how we can avoid that
problem within a fresh implementation.
regards, tom lane
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