Integration of Mercurial into LXR

[andre-littoz]

I'm back and I had time to tackle the directory listing performance issue.

I replaced the query to internal "repo[rev]" and "ctx.manifest()" by a simple extension that returns a constant list of strings. I still have the desperately slow retrieval time with the web server (response time is OK under the shell). But positively, this rules out any problem with internal hg data structures.

Since my simple extension is only a sequence of "ui.write('a_file_name\n')", I questioned ui.write processing time when operating under a web server. I replaced "ui.write" with "sys.stdout.write". Same slow response time.

I then changed the number of strings returned. It appears that total time seems to be proportional to the number of strings (~0.5-0.75 seconds per line!). Response time does not change if only a single string (concatenation of individual lines) is returned.

I am really puzzled and do not guess where to go. I am suspecting something wrong in the pipe mechanism between Python (hg) and Perl (LXR) but an individual file is also read through a pipe (with command "hg cat" or "hg blame") without any noticeably difference in performance compared to other storage engines. Moreover, there should be zillions of apps linking Python and Perl without problem.

My code is very short and, apart from the hg command, is the same as for Subversion (which works like a charm):
sub getdir {
    my ($self, $pathname, $releaseid) = @_;
    my ($node, @dirs, @files);

    my $hgpath = $pathname;
    $hgpath =~ s,/*$,/,;
    # Paths on the hg command lines must not start with a slash
    # to be relative to 'rootpath'. Changes LXR convention.
    $hgpath =~ s,^/+,,;
    open(DIR, $$self{'hg-cmd'}
                . "ls-onelevel -r \"$releaseid\" \"$hgpath\" |")
    || die ("hg subprocess died unexpectedly: $!");

    while($node = <DIR>) {
        chomp($node); # Remode trailing newline
        if (substr($node, -1) eq '/') {
            push(@dirs, $node)
        } else {
            push(@files, $node)
        }
    }
    closedir(DIR);
    return (sort(@dirs), sort(@files));
}

hg-cmd is equal to 'cd '.$rootpath.';HGRCPATH='.$rootpath . '/hg.rc hg ', i.e. change current directory to directory containing .hg and make HGRCPATH point to the correct configuration file so that my private extension is enabled.

Can you see a flaw in the above Perl code? Or a misuse in hg-cmd?



Regards,
André
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