Subject: Re: [PATCH] git-svn: cache max revision in rev_db databases

From: Eric Wong <[email-masked]>
Date: Sun, 10 Jun 2007 14:47:53 -0700

Sam Vilain <[email-masked]> wrote:
> Cache the maximum revision for each rev_db URL rather than looking it
> up each time.  This saves a lot of time when rebuilding indexes on a
> freshly cloned repository.

It looks correct, but I'm not sure how often we can even hit this
optimization to make it worth it.

Any live repositories and benchmarks you've run this on?
(without the rev-list => log patch applied, which would be a big
performance improvement if all log messages were under 16k).

> Signed-off-by: Sam Vilain <[email-masked]>
> ---
>  git-svn.perl |    4 ++++
>  1 files changed, 4 insertions(+), 0 deletions(-)
> 
> diff --git a/git-svn.perl b/git-svn.perl
> index 610563c..c9758a0 100755
> --- a/git-svn.perl
> +++ b/git-svn.perl
> @@ -804,6 +804,7 @@ sub working_head_info {
>  	my ($head, $refs) = @_;
>  	my ($fh, $ctx) = command_output_pipe('log', $head);
>  	my $hash;
> +	my %max;
>  	while (<$fh>) {
>  		if ( m{^commit ($::sha1)$} ) {
>  			$hash = $1;
> @@ -812,11 +813,14 @@ sub working_head_info {
>  		next unless s{^\s+(git-svn-id:)}{$1};
>  		my ($url, $rev, $uuid) = extract_metadata($_);
>  		if (defined $url && defined $rev) {
> +			next if $max{$url} and $max{$url} < $rev;
>  			if (my $gs = Git::SVN->find_by_url($url)) {
>  				my $c = $gs->rev_db_get($rev);
>  				if ($c && $c eq $hash) {
>  					close $fh; # break the pipe
>  					return ($url, $rev, $uuid, $gs);
> +				} else {
> +					$max{$url} ||= $gs->rev_db_max;
>  				}
>  			}
>  		}

-- 
Eric Wong