Re: Fractions in GUC variables

On Jun 14, 2007, at 7:21 AM, Heikki Linnakangas wrote:
> We have these GUC variables that define a fraction of something:
>
> #autovacuum_vacuum_scale_factor = 0.2 # fraction of rel size before
> # vacuum
> #autovacuum_analyze_scale_factor = 0.1 # fraction of rel size before
> # analyze
>
> #bgwriter_lru_percent = 1.0 # 0-100% of LRU buffers scanned/round
> #bgwriter_all_percent = 0.333 # 0-100% of all buffers scanned/round
>
> Autovacuum settings use fractions, and bgwriter settings use a
> percentage. Fortunately these settings are not related so there's
> not too much potential for confusion, but it seems we should have a
> common way to define settings like that.
>
> A nice way would be that the base unit would be a fraction, like in
> the autovacuum settings, but you could add a %-sign to give it as a
> percent, just like you can use KB/MB etc. I'm not sure if we can do
> anything for those without breaking backwards-compatibility, though.
>
> Any ideas? The load distributed checkpoints patch adds one more GUC
> variable like. I'm inclined to follow the example of the bgwriter
> settings because it's more closely related to them, though I like
> the autovacuum style more.

We could create bgwrite_*_fraction (portion?) and deprecate
bgwriter_*_percent...
--
Jim Nasby jim(at)nasby(dot)net
EnterpriseDB http://enterprisedb.com 512.569.9461 (cell)