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git-svn: replace .rev_db with a more space-efficient .rev_map format 

Migrations are done automatically on an as-needed basis when new
revisions are to be fetched.  Stale remote branches do not get
migrated, yet.

However, unless you set noMetadata or useSvkProps it's safe to
just do:

  find $GIT_DIR/svn -name '.rev_db*' -print0 | xargs rm -f

to purge all the old .rev_db files.

The new format is a one-way migration and is NOT compatible with
old versions of git-svn.

This is the replacement for the rev_db format, which was too big
and inefficient for large repositories with a lot of sparse history
(mainly tags).

The format is this:

  - 24 bytes for every record,
    * 4 bytes for the integer representing an SVN revision number
    * 20 bytes representing the sha1 of a git commit

  - No empty padding records like the old format

  - new records are written append-only since SVN revision numbers
    increase monotonically

  - lookups on SVN revision number are done via a binary search

  - Piping the file to xxd(1) -c24 is a good way of dumping it for
    viewing or editing, should the need ever arise.

As with .rev_db, these files are disposable unless noMetadata or
useSvmProps is set.

Signed-off-by: Eric Wong <normalperson@yhbt.net>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This commit is contained in:
Eric Wong 2007-12-08 23:27:41 -08:00 коммит произвёл Junio C Hamano
Родитель 591aa2536f
Коммит 060610c572
3 изменённых файлов: 218 добавлений и 110 удалений
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286
git-svn.perl
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@ -529,7 +529,7 @@ sub cmd_find_rev {
"$head history\n";
}
my $desired_revision = substr($revision_or_hash, 1);
$result = $gs->rev_db_get($desired_revision);
$result = $gs->rev_map_get($desired_revision);
} else {
my (undef, $rev, undef) = cmt_metadata($revision_or_hash);
$result = $rev;
@ -1128,12 +1128,12 @@ sub working_head_info {
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);
my $c = $gs->rev_map_get($rev);
if ($c && $c eq $hash) {
close $fh; # break the pipe
return ($url, $rev, $uuid, $gs);
} else {
$max{$url} ||= $gs->rev_db_max;
$max{$url} ||= $gs->rev_map_max;
}
}
}
@ -1234,6 +1234,8 @@ sub md5sum {
package Git::SVN;
use strict;
use warnings;
use Fcntl qw/:DEFAULT :seek/;
use constant rev_map_fmt => 'NH40';
use vars qw/$default_repo_id $default_ref_id $_no_metadata $_follow_parent
$_repack $_repack_flags $_use_svm_props $_head
$_use_svnsync_props $no_reuse_existing $_minimize_url
@ -1362,7 +1364,7 @@ sub fetch_all {
if ($fetch) {
foreach my $p (sort keys %$fetch) {
my $gs = Git::SVN->new($fetch->{$p}, $repo_id, $p);
my $lr = $gs->rev_db_max;
my $lr = $gs->rev_map_max;
if (defined $lr) {
$base = $lr if ($lr < $base);
}
@ -1897,38 +1899,20 @@ sub last_rev_commit {
return ($rev, $c);
}
}
my $db_path = $self->db_path;
unless (-e $db_path) {
my $map_path = $self->map_path;
unless (-e $map_path) {
($self->{last_rev}, $self->{last_commit}) = (undef, undef);
return (undef, undef);
}
my $offset = -41; # from tail
my $rl;
open my $fh, '<', $db_path or croak "$db_path not readable: $!\n";
sysseek($fh, $offset, 2); # don't care for errors
sysread($fh, $rl, 41) == 41 or return (undef, undef);
chomp $rl;
while (('0' x40) eq $rl && sysseek($fh, 0, 1) != 0) {
$offset -= 41;
sysseek($fh, $offset, 2); # don't care for errors
sysread($fh, $rl, 41) == 41 or return (undef, undef);
chomp $rl;
}
if ($c && $c ne $rl) {
die "$db_path and ", $self->refname,
" inconsistent!:\n$c != $rl\n";
}
my $rev = sysseek($fh, 0, 1) or croak $!;
$rev = ($rev - 41) / 41;
close $fh or croak $!;
($self->{last_rev}, $self->{last_commit}) = ($rev, $c);
return ($rev, $c);
my ($rev, $commit) = $self->rev_map_max;
($self->{last_rev}, $self->{last_commit}) = ($rev, $commit);
return ($rev, $commit);
}
sub get_fetch_range {
my ($self, $min, $max) = @_;
$max ||= $self->ra->get_latest_revnum;
$min ||= $self->rev_db_max;
$min ||= $self->rev_map_max;
(++$min, $max);
}
@ -2073,7 +2057,7 @@ sub do_git_commit {
" was r$lr, but we are about to fetch: ",
"r$log_entry->{revision}!\n";
}
if (my $c = $self->rev_db_get($log_entry->{revision})) {
if (my $c = $self->rev_map_get($log_entry->{revision})) {
croak "$log_entry->{revision} = $c already exists! ",
"Why are we refetching it?\n";
}
@ -2116,14 +2100,14 @@ sub do_git_commit {
die "Failed to commit, invalid sha1: $commit\n";
}
$self->rev_db_set($log_entry->{revision}, $commit, 1);
$self->rev_map_set($log_entry->{revision}, $commit, 1);
$self->{last_rev} = $log_entry->{revision};
$self->{last_commit} = $commit;
print "r$log_entry->{revision}";
if (defined $log_entry->{svm_revision}) {
print " (\@$log_entry->{svm_revision})";
$self->rev_db_set($log_entry->{svm_revision}, $commit,
$self->rev_map_set($log_entry->{svm_revision}, $commit,
0, $self->svm_uuid);
}
print " = $commit ($self->{ref_id})\n";
@ -2465,25 +2449,44 @@ sub set_tree {
}
}
sub rebuild_from_rev_db {
my ($self, $path) = @_;
my $r = -1;
open my $fh, '<', $path or croak "open: $!";
while (<$fh>) {
length($_) == 41 or croak "inconsistent size in ($_) != 41";
chomp($_);
++$r;
next if $_ eq ('0' x 40);
$self->rev_map_set($r, $_);
print "r$r = $_\n";
}
close $fh or croak "close: $!";
unlink $path or croak "unlink: $!";
}
sub rebuild {
my ($self) = @_;
my $db_path = $self->db_path;
return if (-e $db_path && ! -z $db_path);
my $map_path = $self->map_path;
return if (-e $map_path && ! -z $map_path);
return unless ::verify_ref($self->refname.'^0');
if (-f $self->{db_root}) {
rename $self->{db_root}, $db_path or die
"rename $self->{db_root} => $db_path failed: $!\n";
my ($dir, $base) = ($db_path =~ m#^(.*?)/?([^/]+)$#);
symlink $base, $self->{db_root} or die
"symlink $base => $self->{db_root} failed: $!\n";
if ($self->use_svm_props || $self->no_metadata) {
my $rev_db = $self->rev_db_path;
$self->rebuild_from_rev_db($rev_db);
if ($self->use_svm_props) {
my $svm_rev_db = $self->rev_db_path($self->svm_uuid);
$self->rebuild_from_rev_db($svm_rev_db);
}
$self->unlink_rev_db_symlink;
return;
}
print "Rebuilding $db_path ...\n";
my ($log, $ctx) = command_output_pipe("log", '--no-color', $self->refname);
my $latest;
print "Rebuilding $map_path ...\n";
my ($log, $ctx) =
command_output_pipe(qw/rev-list --pretty=raw --no-color --reverse/,
$self->refname, '--');
my $full_url = $self->full_url;
remove_username($full_url);
my $svn_uuid;
my $svn_uuid = $self->ra_uuid;
my $c;
while (<$log>) {
if ( m{^commit ($::sha1)$} ) {
@ -2499,46 +2502,64 @@ sub rebuild {
# if we merged or otherwise started elsewhere, this is
# how we break out of it
if ((defined $svn_uuid && ($uuid ne $svn_uuid)) ||
if (($uuid ne $svn_uuid) ||
($full_url && $url && ($url ne $full_url))) {
next;
}
$latest ||= $rev;
$svn_uuid ||= $uuid;
$self->rev_db_set($rev, $c);
$self->rev_map_set($rev, $c);
print "r$rev = $c\n";
}
command_close_pipe($log, $ctx);
print "Done rebuilding $db_path\n";
print "Done rebuilding $map_path\n";
my $rev_db_path = $self->rev_db_path;
if (-f $self->rev_db_path) {
unlink $self->rev_db_path or croak "unlink: $!";
}
$self->unlink_rev_db_symlink;
}
# rev_db:
# rev_map:
# Tie::File seems to be prone to offset errors if revisions get sparse,
# it's not that fast, either. Tie::File is also not in Perl 5.6. So
# one of my favorite modules is out :< Next up would be one of the DBM
# modules, but I'm not sure which is most portable... So I'll just
# go with something that's plain-text, but still capable of
# being randomly accessed. So here's my ultra-simple fixed-width
# database. All records are 40 characters + "\n", so it's easy to seek
# to a revision: (41 * rev) is the byte offset.
# A record of 40 0s denotes an empty revision.
# And yes, it's still pretty fast (faster than Tie::File).
# modules, but I'm not sure which is most portable...
#
# This is the replacement for the rev_db format, which was too big
# and inefficient for large repositories with a lot of sparse history
# (mainly tags)
#
# The format is this:
# - 24 bytes for every record,
# * 4 bytes for the integer representing an SVN revision number
# * 20 bytes representing the sha1 of a git commit
# - No empty padding records like the old format
# - new records are written append-only since SVN revision numbers
# increase monotonically
# - lookups on SVN revision number are done via a binary search
# - Piping the file to xxd(1) -c24 is a good way of dumping it for
# viewing or editing, should the need ever arise.
#
# These files are disposable unless noMetadata or useSvmProps is set
sub _rev_db_set {
sub _rev_map_set {
my ($fh, $rev, $commit) = @_;
my $offset = $rev * 41;
# assume that append is the common case:
seek $fh, 0, 2 or croak $!;
my $pos = tell $fh;
if ($pos < $offset) {
for (1 .. (($offset - $pos) / 41)) {
print $fh (('0' x 40),"\n") or croak $!;
my $size = (stat($fh))[7];
($size % 24) == 0 or croak "inconsistent size: $size";
if ($size > 0) {
sysseek($fh, -24, SEEK_END) or croak "seek: $!";
my $read = sysread($fh, my $buf, 24) or croak "read: $!";
$read == 24 or croak "read only $read bytes (!= 24)";
my ($last_rev, $last_commit) = unpack(rev_map_fmt, $buf);
if ($last_rev >= $rev) {
croak "last_rev is higher!: $last_rev >= $rev";
}
}
seek $fh, $offset, 0 or croak $!;
print $fh $commit,"\n" or croak $!;
sysseek($fh, 0, SEEK_END) or croak "seek: $!";
syswrite($fh, pack(rev_map_fmt, $rev, $commit), 24) == 24 or
croak "write: $!";
}
sub mkfile {
@ -2551,10 +2572,10 @@ sub mkfile {
}
}
sub rev_db_set {
sub rev_map_set {
my ($self, $rev, $commit, $update_ref, $uuid) = @_;
length $commit == 40 or die "arg3 must be a full SHA1 hexsum\n";
my $db = $self->db_path($uuid);
my $db = $self->map_path($uuid);
my $db_lock = "$db.lock";
my $sig;
if ($update_ref) {
@ -2569,16 +2590,18 @@ sub rev_db_set {
# and we can't afford to lose it because rebuild() won't work
if ($self->use_svm_props || $self->no_metadata) {
$sync = 1;
copy($db, $db_lock) or die "rev_db_set(@_): ",
copy($db, $db_lock) or die "rev_map_set(@_): ",
"Failed to copy: ",
"$db => $db_lock ($!)\n";
} else {
rename $db, $db_lock or die "rev_db_set(@_): ",
rename $db, $db_lock or die "rev_map_set(@_): ",
"Failed to rename: ",
"$db => $db_lock ($!)\n";
}
open my $fh, '+<', $db_lock or die "Couldn't open $db_lock: $!\n";
_rev_db_set($fh, $rev, $commit);
sysopen(my $fh, $db_lock, O_RDWR | O_APPEND | O_CREAT)
or croak "Couldn't open $db_lock: $!\n";
_rev_map_set($fh, $rev, $commit);
if ($sync) {
$fh->flush or die "Couldn't flush $db_lock: $!\n";
$fh->sync or die "Couldn't sync $db_lock: $!\n";
@ -2589,7 +2612,7 @@ sub rev_db_set {
command_noisy('update-ref', '-m', "r$rev",
$self->refname, $commit);
}
rename $db_lock, $db or die "rev_db_set(@_): ", "Failed to rename: ",
rename $db_lock, $db or die "rev_map_set(@_): ", "Failed to rename: ",
"$db_lock => $db ($!)\n";
delete $LOCKFILES{$db_lock};
if ($update_ref) {
@ -2599,29 +2622,61 @@ sub rev_db_set {
}
}
sub rev_db_max {
sub rev_map_max {
my ($self) = @_;
$self->rebuild;
my $db_path = $self->db_path;
my @stat = stat $db_path or return 0;
($stat[7] % 41) == 0 or die "$db_path inconsistent size: $stat[7]\n";
my $max = $stat[7] / 41;
(($max > 0) ? $max - 1 : 0);
my $map_path = $self->map_path;
stat $map_path or return wantarray ? (0, undef) : 0;
sysopen(my $fh, $map_path, O_RDONLY) or croak "open: $!";
my $size = (stat($fh))[7];
($size % 24) == 0 or croak "inconsistent size: $size";
if ($size == 0) {
close $fh or croak "close: $!";
return wantarray ? (0, undef) : 0;
}
sysseek($fh, -24, SEEK_END);
sysread($fh, my $buf, 24) == 24 or croak "read: $!";
close $fh or croak "close: $!";
my ($r, $c) = unpack(rev_map_fmt, $buf);
wantarray ? ($r, $c) : $r;
}
sub rev_db_get {
sub rev_map_get {
my ($self, $rev, $uuid) = @_;
my $ret;
my $offset = $rev * 41;
my $db_path = $self->db_path($uuid);
return undef unless -e $db_path;
open my $fh, '<', $db_path or croak $!;
if (sysseek($fh, $offset, 0) == $offset) {
my $read = sysread($fh, $ret, 40);
$ret = undef if ($read != 40 || $ret eq ('0'x40));
my $map_path = $self->map_path($uuid);
return undef unless -e $map_path;
sysopen(my $fh, $map_path, O_RDONLY) or croak "open: $!";
my $size = (stat($fh))[7];
($size % 24) == 0 or croak "inconsistent size: $size";
if ($size == 0) {
close $fh or croak "close: $fh";
return undef;
}
close $fh or croak $!;
$ret;
my ($l, $u) = (0, $size - 24);
my ($r, $c, $buf);
while ($l <= $u) {
my $i = int(($l/24 + $u/24) / 2) * 24;
sysseek($fh, $i, SEEK_SET) or croak "seek: $!";
sysread($fh, my $buf, 24) == 24 or croak "read: $!";
my ($r, $c) = unpack('NH40', $buf);
if ($r < $rev) {
$l = $i + 24;
} elsif ($r > $rev) {
$u = $i - 24;
} else { # $r == $rev
close($fh) or croak "close: $!";
return $c;
}
}
close($fh) or croak "close: $!";
undef;
}
# Finds the first svn revision that exists on (if $eq_ok is true) or
@ -2633,7 +2688,7 @@ sub find_rev_before {
--$rev unless $eq_ok;
$min_rev ||= 1;
while ($rev >= $min_rev) {
if (my $c = $self->rev_db_get($rev)) {
if (my $c = $self->rev_map_get($rev)) {
return ($rev, $c);
}
--$rev;
@ -2648,9 +2703,9 @@ sub find_rev_before {
sub find_rev_after {
my ($self, $rev, $eq_ok, $max_rev) = @_;
++$rev unless $eq_ok;
$max_rev ||= $self->rev_db_max();
$max_rev ||= $self->rev_map_max;
while ($rev <= $max_rev) {
if (my $c = $self->rev_db_get($rev)) {
if (my $c = $self->rev_map_get($rev)) {
return ($rev, $c);
}
++$rev;
@ -2673,13 +2728,32 @@ sub _new {
bless {
ref_id => $ref_id, dir => $dir, index => "$dir/index",
path => $path, config => "$ENV{GIT_DIR}/svn/config",
db_root => "$dir/.rev_db", repo_id => $repo_id }, $class;
map_root => "$dir/.rev_map", repo_id => $repo_id }, $class;
}
sub db_path {
# for read-only access of old .rev_db formats
sub unlink_rev_db_symlink {
my ($self) = @_;
my $link = $self->rev_db_path;
$link =~ s/\.[\w-]+$// or croak "missing UUID at the end of $link";
if (-l $link) {
unlink $link or croak "unlink: $link failed!";
}
}
sub rev_db_path {
my ($self, $uuid) = @_;
my $db_path = $self->map_path($uuid);
$db_path =~ s{/\.rev_map\.}{/\.rev_db\.}
or croak "map_path: $db_path does not contain '/.rev_map.' !";
$db_path;
}
# the new replacement for .rev_db
sub map_path {
my ($self, $uuid) = @_;
$uuid ||= $self->ra_uuid;
"$self->{db_root}.$uuid";
"$self->{map_root}.$uuid";
}
sub uri_encode {
@ -3763,7 +3837,7 @@ sub gs_fetch_loop_common {
foreach my $gs ($self->match_globs(\%exists, $paths,
$globs, $r)) {
if ($gs->rev_db_max >= $r) {
if ($gs->rev_map_max >= $r) {
next;
}
next unless $gs->match_paths($paths, $r);
@ -3789,12 +3863,6 @@ sub gs_fetch_loop_common {
$ra_invalid = undef;
}
}
# pre-fill the .rev_db since it'll eventually get filled in
# with '0' x40 if something new gets committed
foreach my $gs (@$gsv) {
next if defined $gs->rev_db_get($max);
$gs->rev_db_set($max, 0 x40);
}
foreach my $g (@$globs) {
my $k = "svn-remote.$g->{remote}.$g->{t}-maxRev";
Git::SVN::tmp_config($k, $max);
@ -4030,7 +4098,7 @@ sub git_svn_log_cmd {
push @cmd, @log_opts;
if (defined $r_max && $r_max == $r_min) {
push @cmd, '--max-count=1';
if (my $c = $gs->rev_db_get($r_max)) {
if (my $c = $gs->rev_map_get($r_max)) {
push @cmd, $c;
}
} elsif (defined $r_max) {
@ -4311,6 +4379,16 @@ package Git::SVN::Migration;
# --use-separate-remotes option in git-clone (now default)
# - we do not automatically migrate to this (following
# the example set by core git)
#
# v5 layout: .rev_db.$UUID => .rev_map.$UUID
# - newer, more-efficient format that uses 24-bytes per record
# with no filler space.
# - use xxd -c24 < .rev_map.$UUID to view and debug
# - This is a one-way migration, repositories updated to the
# new format will not be able to use old git-svn without
# rebuilding the .rev_db. Rebuilding the rev_db is not
# possible if noMetadata or useSvmProps are set; but should
# be no problem for users that use the (sensible) defaults.
use strict;
use warnings;
use Carp qw/croak/;

26
t/lib-git-svn.sh
Просмотреть файл

@ -82,3 +82,29 @@ stop_httpd () {
test -z "$SVN_HTTPD_PORT" && return
"$SVN_HTTPD_PATH" -f "$GIT_DIR"/httpd.conf -k stop
}
convert_to_rev_db () {
perl -w -- - "$@" <<\EOF
use strict;
@ARGV == 2 or die "Usage: convert_to_rev_db <input> <output>";
open my $wr, '+>', $ARGV[1] or die "$!: couldn't open: $ARGV[1]";
open my $rd, '<', $ARGV[0] or die "$!: couldn't open: $ARGV[0]";
my $size = (stat($rd))[7];
($size % 24) == 0 or die "Inconsistent size: $size";
while (sysread($rd, my $buf, 24) == 24) {
my ($r, $c) = unpack('NH40', $buf);
my $offset = $r * 41;
seek $wr, 0, 2 or die $!;
my $pos = tell $wr;
if ($pos < $offset) {
for (1 .. (($offset - $pos) / 41)) {
print $wr (('0' x 40),"\n") or die $!;
}
}
seek $wr, $offset, 0 or die $!;
print $wr $c,"\n" or die $!;
}
close $wr or die $!;
close $rd or die $!;
EOF
}

16
t/t9107-git-svn-migrate.sh
Просмотреть файл

@ -97,15 +97,19 @@ test_expect_success 'migrate --minimize on old inited layout' "
grep '^:refs/remotes/git-svn' fetch.out
"
test_expect_success ".rev_db auto-converted to .rev_db.UUID" "
test_expect_success ".rev_db auto-converted to .rev_map.UUID" "
git-svn fetch -i trunk &&
expect=$GIT_DIR/svn/trunk/.rev_db.* &&
test -z \"\$(ls $GIT_DIR/svn/trunk/.rev_db.* 2>/dev/null)\" &&
expect=\"\$(ls $GIT_DIR/svn/trunk/.rev_map.*)\" &&
test -n \"\$expect\" &&
mv \$expect $GIT_DIR/svn/trunk/.rev_db &&
rev_db=\$(echo \$expect | sed -e 's,_map,_db,') &&
convert_to_rev_db \$expect \$rev_db &&
rm -f \$expect &&
test -f \$rev_db &&
git-svn fetch -i trunk &&
test -L $GIT_DIR/svn/trunk/.rev_db &&
test -f \$expect &&
cmp \$expect $GIT_DIR/svn/trunk/.rev_db
test -z \"\$(ls $GIT_DIR/svn/trunk/.rev_db.* 2>/dev/null)\" &&
test ! -e $GIT_DIR/svn/trunk/.rev_db &&
test -f \$expect
"
test_done