Re: Online enabling of checksums

On 03/27/2018 08:56 AM, Magnus Hagander wrote:
> On Mon, Mar 26, 2018 at 10:09 PM, Tomas Vondra
> <tomas(dot)vondra(at)2ndquadrant(dot)com <mailto:tomas(dot)vondra(at)2ndquadrant(dot)com>> wrote:
>
> Hi,
>
> I see enable_data_checksums() does this:
>
>     if (cost_limit <= 0)
>         ereport(ERROR,
>                 (errmsg("cost limit must be a positive value")));
>
> Is there a reason not to allow -1 (no limit), just like for vacuum_cost?
>
>
> Eh. vaccum_cost_limit cannot be set to -1 (1 is the lowest). Neither can
> vacuum_cost_delay -- it is set to *0* to disable it (which is how the
> cost_delay parameter is handled here as well).
>
> Are you thinking autovacuum_vacuum_cost_limit where -1 means "use
> vacuum_cost_limit"?
>
> The reason to disallow cost_limit=0 is to avoid divide-by-zero. We could
> allow -1 and have it mean "use vacuum_cost_limit", but I'm not sure how
> relevant that really would be in this context?
>

D'oh! You're right, of course.

regards

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