Re: Relation between parameters in postgresql.conf file!!

Hi Pavan,

Go through this link. hope this will help you.

https://www.percona.com/blog/2018/08/10/tuning-autovacuum-in-postgresql-and-autovacuum-internals/

<http://www.shreeyansh.com>

On Fri, Nov 2, 2018 at 12:09 PM pavan95 <pavan(dot)postgresdba(at)gmail(dot)com> wrote:

> Hi all,
>
> I have gone through the below parameters:
>
> 1. vacuum_cost_page_hit
> 2. vacuum_cost_page_miss
> 3. vacuum_cost_page_dirty
>
> Got confused by reading them from the documentation. I am unable to
> understand why the values 1, 10, 20 are assigned to them(on what basis
> those
> values have been assigned).
>
> Is there some relation between these parameters and the below parameters?
>
> 1. autovacuum_vacuum_scale_factor=0.2(20%)
> 2. autovacuum_analyze_scale_factor=0.1(10%)
>
> From the below description:
>
> >vacuum_cost_page_hit (integer)
> >The estimated cost for vacuuming a buffer found in the shared buffer
> cache.
> It represents the cost to lock the buffer pool, lookup the shared hash
> table
> and scan the content of the page. The default value is one
> 1. Does the vacuum operate on the buffer pool(memory)? Assuming it is
> operated on the data files!!!
> 2. What does the sentence "lock the buffer pool, lookup the shared hash
> table and scan the content of the page" refers to??
>
> >vacuum_cost_page_dirty (integer)
> >The estimated cost charged when vacuum modifies a block that was
> previously
> clean. It represents the extra I/O required to flush the dirty block out to
> disk again. The default value is 20.
> What does actually happen here?? Why does this generate extra I/O??
>
> What is the meaning of the sentence "It represents the extra I/O required
> to
> flush the dirty block out to disk again"?? Why does vacuum flush the dirty
> block to disk when writer process does that?
>
> Please clarify!!!!!! Thanks in Advance.
>
>
> Regards,
> Pavan
>
>
>
> --
> Sent from:
> http://www.postgresql-archive.org/PostgreSQL-admin-f2076596.html
>
>