RE: Protect syscache from bloating with negative cache entries

From: "Tsunakawa, Takayuki" <tsunakawa(dot)takay(at)jp(dot)fujitsu(dot)com>
To: 'Bruce Momjian' <bruce(at)momjian(dot)us>, Tomas Vondra <tomas(dot)vondra(at)2ndquadrant(dot)com>
Cc: "andres(at)anarazel(dot)de" <andres(at)anarazel(dot)de>, Robert Haas <robertmhaas(at)gmail(dot)com>, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>, Kyotaro HORIGUCHI <horiguchi(dot)kyotaro(at)lab(dot)ntt(dot)co(dot)jp>, "Ideriha, Takeshi" <ideriha(dot)takeshi(at)jp(dot)fujitsu(dot)com>, "pgsql-hackers(at)lists(dot)postgresql(dot)org" <pgsql-hackers(at)lists(dot)postgresql(dot)org>, "alvherre(at)alvh(dot)no-ip(dot)org" <alvherre(at)alvh(dot)no-ip(dot)org>, "michael(dot)paquier(at)gmail(dot)com" <michael(dot)paquier(at)gmail(dot)com>, "david(at)pgmasters(dot)net" <david(at)pgmasters(dot)net>, "craig(at)2ndquadrant(dot)com" <craig(at)2ndquadrant(dot)com>
Subject: RE: Protect syscache from bloating with negative cache entries
Date: 2019-02-14 01:31:49
Message-ID: 0A3221C70F24FB45833433255569204D1FB98603@G01JPEXMBYT05
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From: Bruce Momjian [mailto:bruce(at)momjian(dot)us]
> > That being said, having a "minimal size" threshold before starting with
> > the time-based eviction may be a good idea.
>
> Agreed. I see the minimal size as a way to keep the systems tables in
> cache, which we know we will need for the next query.

Isn't it the maximum size, not minimal size? Maximum size allows to keep desired amount of system tables in memory as well as to control memory consumption to avoid out-of-memory errors (OS crash!). I'm wondering why people want to take a different approach to catcatch, which is unlike other PostgreSQL memory e.g. shared_buffers, temp_buffers, SLRU buffers, work_mem, and other DBMSs.

Regards
Takayuki Tsunakawa

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