Re: need suggestion on querying big tables - Mailing list pgsql-admin

From Ron
Subject Re: need suggestion on querying big tables
Date
Msg-id 668ca86c-3e66-e3ac-3b2e-1b716ce3859f@gmail.com
Whole thread Raw
In response to Re: need suggestion on querying big tables  (Tom Lane <tgl@sss.pgh.pa.us>)
List pgsql-admin
On 12/6/22 09:03, Tom Lane wrote:
> Ron <ronljohnsonjr@gmail.com> writes:
>> You've set effective_cache_size to 83%, when it should be at most 20%.
> I think you're confusing effective_cache_size with the size of
> shared buffers.  It's meant to be an estimate of the total disk
> cache space available, in both shared buffers and OS caches.
> In any case, it's a fairly spongy parameter.  It doesn't correspond
> to any allocation actually made or requested in Postgres; it just
> serves to tweak the planner's guesses about how expensive repeated
> indexscans are likely to be.  83% of available RAM might be too
> much, but it's probably not causing any real problems.

The docs say that ECS is an estimate of how much cache one query can use, 
no?  If more than one query is running on a server at a time, then wouldn't 
a huge ECS confuse things?

-- 
Angular momentum makes the world go 'round.



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