Re: need suggestion on querying big tables

> On Dec 6, 2022, at 8:51 AM, Ron <ronljohnsonjr(at)gmail(dot)com> wrote:
>
> https://www.postgresql.org/docs/11/runtime-config-query.html
>
> effective_cache_size is how much RAM a single query gets. "When setting this parameter you should consider both PostgreSQL's shared buffers".
>
> https://www.postgresql.org/docs/11/runtime-config-resource.html
>
> "a reasonable starting value for shared_buffers is 25% of the memory in your system. There are some workloads where even larger settings for shared_buffers are effective, but because PostgreSQL also relies on the operating system cache, it is unlikely that an allocation of more than 40% of RAM to shared_buffers will work better than a smaller amount."
>
> You've set effective_cache_size to 83%, when it should be at most 20%.

effective_cache_size is a hint as to how much RAM is available for the operating system file cache after all other uses are taken into account.