On Fri, 12 Dec 2008, Sébastien Cevey wrote:
> At Fri, 12 Dec 2008 01:13:45 +0100, Jakub Narebski wrote:
>
> > I just tried, it works but we first need to sort @projects by
> > category.
> >
> > I don't understand.
> > [...]
> > I propose to change it to:
>
> Well in my previous iteration of the patch (v3), the printing of
> projects with categories is done using:
>
> foreach my $cat (sort keys %categories) {
>
> So everything was already sorted by category (and then by whichever
> property you picked inside each category). You seemed okay with it,
> but requested that I documented that behaviour in the commit log.
But this does not mean that sorting by categories is necessary, or
even wanted (see below). This foreach _sorts_ by categories as primary
key using kind of bucket sort algorithm.
> To maintain the same result with your proposed change (which is what I
> submitted in my patch), we need to sort by categories first (AFAIK
> Perl sort retains the original order inside equivalence classes of
> comparison key?), otherwise splice(projlist, from, to) doesn't return
> the expected subset.
Perl requires "use sort 'stable';" pragma to ensure stable sort.
And no, we don't need to sort by categories first. Let me explain
in more detail a bit.
Let us assume that $from and $to is actually used to divide projects
list into categories (which goal is incompatible with searching
projects, limiting to given tag/tagset and hiding forked as it is done
now, at the display time; it has to be done _before_ pagination).
They are used to display first page, i.e. repositories numbered 1..N
in current ordering, or N..2*N, or 2*N..3*N to show next pages. Let us
have the following project list:
Project Category
---------------------------
1 a
2 b
3 b
4 a
If categories are not shown, and page limit is 2, then project would
be displayed like this:
page 1 page 2
------ ------
1 3
2 4
Now _without_ sorting by category upfront, those pages would look like
the following if grouping by category is enabled:
A.page 1 page 2
------ ------
[a] [a]
1 4
[b] [b]
2 3
What is not visible in this example is that projects inside category
would be sorted by given order.
Now if you would sort by categories _before_ pagination, like you
(from what I understand) proposed, you would have (assuming that
you used "use sort 'stable'" inside block):
Project Category
---------------------------
1 a
4 a
2 b
3 b
Pagination would then look like the following:
B.page 1 page 2
------ ------
[a] [b]
1 2
4 3
Now which result you consider correct depends on the point of view.
First is sort, paginate, sort; second is sort, sort, paginate.
First have first N repositories in given order on first page, perhaps
reordered a bit by categories, second doesn't have this feature.
I think that the case A is more correct, but you might disagree.
Let us change example a bit:
Project Category
---------------------------
1 b
2 a
3 a
4 b
A.page 1 page 2
------ ------
[a] [a]
2 3
[b] [b]
1 4
B.page 1 page 2
------ ------
[a] [b]
2 1
3 4
P.S. It is IMHO better to use
for (my $i = $from; $i <= $to; $i++) {
than the style which is not used elsewhere in gitweb, from what
I remember
foreach my $i ($from..$to) {
I might also be inefficient as it generates temporary array which
might be quite big; I don't know if Perl 5.8.x, the oldest version
one can sensibly use with gitweb I think, has this bug or not.
--
Jakub Narebski
Poland
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