Subject: Re: Protect syscache from bloating with negative cache entries
To: "Tsunakawa, Takayuki" <tsunakawa.takay@jp.fujitsu.com>,
 'Kyotaro HORIGUCHI' <horiguchi.kyotaro@lab.ntt.co.jp>
Cc: "alvherre@2ndquadrant.com" <alvherre@2ndquadrant.com>,
 "bruce@momjian.us" <bruce@momjian.us>,
 "andres@anarazel.de" <andres@anarazel.de>,
 "robertmhaas@gmail.com" <robertmhaas@gmail.com>,
 "tgl@sss.pgh.pa.us" <tgl@sss.pgh.pa.us>,
 "Ideriha, Takeshi" <ideriha.takeshi@jp.fujitsu.com>,
 "pgsql-hackers@lists.postgresql.org" <pgsql-hackers@lists.postgresql.org>,
 "michael.paquier@gmail.com" <michael.paquier@gmail.com>,
 "david@pgmasters.net" <david@pgmasters.net>,
 "craig@2ndquadrant.com" <craig@2ndquadrant.com>
References: <20190207.152418.139132570.horiguchi.kyotaro@lab.ntt.co.jp>
 <20190207.211845.263152487.horiguchi.kyotaro@lab.ntt.co.jp>
 <74386116-0bc5-84f2-e614-0cff19aca2de@2ndquadrant.com>
 <20190212.203510.100151050.horiguchi.kyotaro@lab.ntt.co.jp>
 <0A3221C70F24FB45833433255569204D1FB97B80@G01JPEXMBYT05>
From: Tomas Vondra <tomas.vondra@2ndquadrant.com>
Message-ID: <46935902-7753-6235-690f-2ce657ae2a5f@2ndquadrant.com>
Date: Fri, 15 Feb 2019 16:44:27 +0100
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On 2/13/19 1:23 AM, Tsunakawa, Takayuki wrote:
> From: Kyotaro HORIGUCHI [mailto:horiguchi.kyotaro@lab.ntt.co.jp]
>> I'm at a loss how call syscache for users. I think it is "catalog
>> cache". The most basic component is called catcache, which is
>> covered by the syscache layer, both of then are not revealed to
>> users, and it is shown to user as "catalog cache".
>>
>> "catalog_cache_prune_min_age", "catalog_cache_memory_target", (if
>> exists) "catalog_cache_entry_limit" and
>> "catalog_cache_prune_ratio" make sense?
> 
> PostgreSQL documentation uses "system catalog" in its table of contents, so syscat_cache_xxx would be a bit more familiar?  I'm for either catalog_ and syscat_, but what name shall we use for the relation cache?  catcache and relcache have different element sizes and possibly different usage patterns, so they may as well have different parameters just like MySQL does.  If we follow that idea, then the name would be relation_cache_xxx.  However, from the user's viewpoint, the relation cache is also created from the system catalog like pg_class and pg_attribute...
> 

I think "catalog_cache_..." is fine. If we end up with a similar
patchfor relcache, we can probably call it "relation_cache_".

I'd be OK even with "system_catalog_cache_..." - I don't think it's
overly long (better to have a longer but descriptive name), and "syscat"
just seems like unnecessary abbreviation.

regards

-- 
Tomas Vondra                  http://www.2ndQuadrant.com
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services