Re: Protect syscache from bloating with negative cache entries

[Tomas Vondra]

On 2/13/19 1:23 AM, Tsunakawa, Takayuki wrote:
> From: Kyotaro HORIGUCHI [mailto:horiguchi.kyot...@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