[arch-general] Implement sql/sqlite database for pacman local database

[Chi-Hsuan Yen]

On Sat, Oct 22, 2016 at 1:54 AM, Robin via arch-general <
arch-general at archlinux.org> wrote:

> Hi,
>
> > I was curious why does 'pacman -Q' operations took longer than 'apt'
> > counterparts.
> Sounds interesting but I have a few question about how did you measure
> this and how big the difference is. (Shouldn't be that big). Would be great
> if you provide more information on the comparability of you systems and the
> tools you used for tracing.
> Maybe there are other reasons why it is slow on your installation ?
>
> > For long term pacman development road map, it would be better to use
> > single sql based database for tracking locally installed packages
> > instead of keeping directories of every installed packages.
> I am not sure if a sql based database would be a good solution if you
> where right. It adds much more complexity and also a dependencies on $SQL
> backend. For me as a semi-professional arch user this would be worse than a
> maybe "not that fast" package dB querying.
>
> Regards,
>  Robin


Sometimes I have a similar problem, too. When the system just boots up, or
I just exploits my disk (for example building Firefox), pacman-related
files are moved out of the disk cache, so it needs some time to read them
all from the disk. Here's a simple performance test:

$ sudo -v && time pacman -Q linux && sudo sync && sudo sync && echo 3 |
sudo tee /proc/sys/vm/drop_caches && time pacman -Q linux
[sudo] password for yen:
linux 4.8.3-1
pacman --color=auto -Q linux  0.00s user 0.00s system 2% cpu 0.121 total
3
linux 4.8.3-1
pacman --color=auto -Q linux  0.00s user 0.01s system 0% cpu 1.229 total

The difference is more than 10 times. I use a 5-year-old HDD. I guess on
even older machines things are worse.

Regards,

Yen Chi Hsuan