Re: effective_cache_size

On 16/10/2018 17:38, Bruce Momjian wrote:
> diff --git a/src/backend/utils/misc/guc.c b/src/backend/utils/misc/guc.c
> index 2317e8b..e471d7f 100644
> --- a/src/backend/utils/misc/guc.c
> +++ b/src/backend/utils/misc/guc.c
> @@ -2987,10 +2987,9 @@ static struct config_int ConfigureNamesInt[] =
>  
>      {
>          {"effective_cache_size", PGC_USERSET, QUERY_TUNING_COST,
> -            gettext_noop("Sets the planner's assumption about the size of the disk cache."),
> -            gettext_noop("That is, the portion of the kernel's disk cache that "
> -                         "will be used for PostgreSQL data files. This is measured in disk "
> -                         "pages, which are normally 8 kB each."),
> +            gettext_noop("Sets the planner's assumption about the size of the data cache."),
> +            gettext_noop("That is, the size of the cache used for PostgreSQL data files. "
> +                         "This is measured in disk pages, which are normally 8 kB each."),
>              GUC_UNIT_BLOCKS,
>          },
>          &effective_cache_size,

This change completely loses the context that this is the kernel's/host
system's memory size.  What is "data cache"?  I think this is a bad
change.  I know it's confusing, but the old description at least had
some basis in terms that are known to the user.

-- 
Peter Eisentraut              http://www.2ndQuadrant.com/
PostgreSQL Development, 24x7 Support, Remote DBA, Training & Services