2012/11/20 Heikki Linnakangas <hlinnakangas@vmware.com>:
> On 19.11.2012 15:17, Pavel Stehule wrote:
>>
>> I tested this patch and I can confirm, so this patch can increase
>> speed about 16-22% (depends on IO waits, load type).
>
>
> Thanks for the review.
>
> I spent some more time on this, continuing with the thought that perhaps it
> would be better if get_str_from_var() didn't scribble on its input. I ended
> up with the attached patch, which contains a bunch of small tweaks:
>
> * Add init_var_from_num() function. This is the same as
> set_var_from_num_nocopy in the original patch, but it doesn't require the
> caller to have called init_var() first. IMHO this makes the calling code
> slightly more readable. Also, it's now more evident what these vars are: the
> digits array points to original array in the original Datum, but 'buf' is
> NULL. This is the same arrangement that's used in the constant NumericVars
> like const_zero.
>
> * get_str_from_var() no longer scribbles on its input. I noticed that it's
> always called with a dscale that comes from the input var itself. In other
> words, the rounding was unnecessary to begin with. I simply removed the
> dscale argument and the round_var() call from get_str_from_var(). If a
> someone wants to display a string with different dscale in the future, he
> can simply call round_var() before get_str_from_var().
>
> * numericvar_to_int8() no long scribbles on its input either. It creates a
> temporary copy to avoid that. To compensate, the callers no longer need to
> create a temporary copy, so the net # of pallocs is the same, but this is
> nicer. (there's room for a micro-optimization to avoid making the temporary
> copy numericvar_to_int8() when the argument is already suitably rounded - I
> left that our for now, dunno if it would make any difference in practice)
>
> * use a constant for the number 10 in get_str_from_var_sci(), when
> calculating 10^exponent. Saves a palloc() and some cycles to convert integer
> 10 to numeric.
>
> Comments? Assuming no-one sees some fatal flaw in this, I'll commit this
> tomorrow.
I have no objections
all regression tests passed, no warnings - has a sense
Regards
Pavel
>
> - Heikki
