Re: need suggestion on querying big tables

On 12/6/22 09:03, Tom Lane wrote:
> Ron <ronljohnsonjr(at)gmail(dot)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?

--
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