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.vondra@2ndquadrant.com <mailto:tomas.vondra@2ndquadrant.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
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