That comparison was basically what I was investigating - on-the-fly calcs 
taking minutes, vs fractions of a seconds to retrieve from a DB.
Add to that... to do the calculation you might need to retrieve twice as 
much data anyway and redo the day-archive calculations every cycle.

As you suggest, I am sure there are ways, such as numpy perhaps, that allow 
you to handle vectors far more efficiently, but I am doubtful that it 
would  be worth the trouble. Especially now that sqlite can add columns far 
more easily.

Cameron.  

On Friday 29 December 2023 at 12:42:43 am UTC+10 Greg Troxel wrote:

> "'Cameron D' via weewx-development" <[email protected]>
> writes:
>
> > My assumption would be that any derivable value that you want to plot 
> > should be a column in the database. Even if you could speed it up, the 
> > calculation it would need to be by a factor approaching 100 to be a 
> useful 
> > choice.
> > I think that using derived parameters for only a "current" display 
> should 
> > be OK, but as soon as you want to plot it or include it in stats then 
> each 
> > report has to process the year's worth.
>
> While I more or less see your point, have you benchmarked the cost of
> extra database columns vs computing on the fly? In most computers these
> days I would expect CPU is much faster than storage.
>
> Stats though there is a stronger argument for storing it.
> 1
>

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