X-Git-Url: http://www.git.stargrave.org/?a=blobdiff_plain;f=lib%2FPublicInbox%2FV2Writable.pm;h=3329d79fa77b56690be7cd45bac12b9fa53674c6;hb=4bb34fb8f29530f6bda5f0d563a74f6289ac312d;hp=b6532ac5c9476540017f9ee9757cdc7c533cfb46;hpb=b4d127cb83230fe5cee0dcecb573107ad96a7c4c;p=public-inbox.git

diff --git a/lib/PublicInbox/V2Writable.pm b/lib/PublicInbox/V2Writable.pm
index b6532ac5..3329d79f 100644
--- a/lib/PublicInbox/V2Writable.pm
+++ b/lib/PublicInbox/V2Writable.pm
@@ -2,6 +2,7 @@
 # License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
 
 # This interface wraps and mimics PublicInbox::Import
+# Used to write to V2 inboxes (see L<public-inbox-v2-format(5)>).
 package PublicInbox::V2Writable;
 use strict;
 use warnings;
@@ -10,70 +11,113 @@ use PublicInbox::SearchIdxPart;
 use PublicInbox::MIME;
 use PublicInbox::Git;
 use PublicInbox::Import;
-use PublicInbox::MID qw(mids);
+use PublicInbox::MID qw(mids references);
 use PublicInbox::ContentId qw(content_id content_digest);
 use PublicInbox::Inbox;
-use PublicInbox::OverIdxFork;
+use PublicInbox::OverIdx;
 use PublicInbox::Msgmap;
+use PublicInbox::Spawn qw(spawn);
+use PublicInbox::SearchIdx;
 use IO::Handle;
 
 # an estimate of the post-packed size to the raw uncompressed size
 my $PACKING_FACTOR = 0.4;
 
-# assume 2 cores if GNU nproc(1) is not available
-sub nproc () {
-	int($ENV{NPROC} || `nproc 2>/dev/null` || 2);
-}
-
-sub new {
-	my ($class, $v2ibx, $creat) = @_;
-	my $dir = $v2ibx->{mainrepo} or die "no mainrepo in inbox\n";
-	unless (-d $dir) {
-		if ($creat) {
-			require File::Path;
-			File::Path::mkpath($dir);
-		} else {
-			die "$dir does not exist\n";
+# SATA storage lags behind what CPUs are capable of, so relying on
+# nproc(1) can be misleading and having extra Xapian partions is a
+# waste of FDs and space.  It can also lead to excessive IO latency
+# and slow things down.  Users on NVME or other fast storage can
+# use the NPROC env or switches in our script/public-inbox-* programs
+# to increase Xapian partitions.
+our $NPROC_MAX_DEFAULT = 4;
+
+sub nproc_parts ($) {
+	my ($creat_opt) = @_;
+	if (ref($creat_opt) eq 'HASH') {
+		if (defined(my $n = $creat_opt->{nproc})) {
+			return $n
 		}
 	}
 
+	my $n = $ENV{NPROC};
+	if (!$n) {
+		chomp($n = `nproc 2>/dev/null`);
+		# assume 2 cores if GNU nproc(1) is not available
+		$n = 2 if !$n;
+		$n = $NPROC_MAX_DEFAULT if $NPROC_MAX_DEFAULT > 4;
+	}
+
+	# subtract for the main process and git-fast-import
+	$n -= 1;
+	$n < 1 ? 1 : $n;
+}
+
+sub count_partitions ($) {
+	my ($self) = @_;
 	my $nparts = 0;
-	my $xpfx = "$dir/xap" . PublicInbox::Search::SCHEMA_VERSION;
+	my $xpfx = $self->{xpfx};
 
 	# always load existing partitions in case core count changes:
+	# Also, partition count may change while -watch is running
+	# due to -compact
 	if (-d $xpfx) {
 		foreach my $part (<$xpfx/*>) {
-			-d $part && $part =~ m!/\d+\z! or next;
+			-d $part && $part =~ m!/[0-9]+\z! or next;
 			eval {
 				Search::Xapian::Database->new($part)->close;
 				$nparts++;
 			};
 		}
 	}
-	$nparts = nproc() if ($nparts == 0);
+	$nparts;
+}
+
+sub new {
+	# $creat may be any true value, or 0/undef.  A hashref is true,
+	# and $creat->{nproc} may be set to an integer
+	my ($class, $v2ibx, $creat) = @_;
+	my $dir = $v2ibx->{mainrepo} or die "no mainrepo in inbox\n";
+	unless (-d $dir) {
+		if ($creat) {
+			require File::Path;
+			File::Path::mkpath($dir);
+		} else {
+			die "$dir does not exist\n";
+		}
+	}
 
 	$v2ibx = PublicInbox::InboxWritable->new($v2ibx);
+	$v2ibx->umask_prepare;
+
+	my $xpfx = "$dir/xap" . PublicInbox::Search::SCHEMA_VERSION;
 	my $self = {
 		-inbox => $v2ibx,
 		im => undef, #  PublicInbox::Import
-		partitions => $nparts,
 		parallel => 1,
 		transact_bytes => 0,
-		over => PublicInbox::OverIdxFork->new("$xpfx/over.sqlite3"),
+		current_info => '',
+		xpfx => $xpfx,
+		over => PublicInbox::OverIdx->new("$xpfx/over.sqlite3", 1),
 		lock_path => "$dir/inbox.lock",
-		# limit each repo to 1GB or so
+		# limit each git repo (epoch) to 1GB or so
 		rotate_bytes => int((1024 * 1024 * 1024) / $PACKING_FACTOR),
+		last_commit => [], # git repo -> commit
 	};
+	$self->{partitions} = count_partitions($self) || nproc_parts($creat);
 	bless $self, $class;
 }
 
+# public (for now?)
 sub init_inbox {
-	my ($self, $parallel) = @_;
+	my ($self, $parallel, $skip_epoch) = @_;
 	$self->{parallel} = $parallel;
 	$self->idx_init;
-	my $max_git = -1;
-	git_dir_latest($self, \$max_git);
-	$self->git_init($max_git >= 0 ? $max_git : 0);
+	my $epoch_max = -1;
+	git_dir_latest($self, \$epoch_max);
+	if (defined $skip_epoch && $epoch_max == -1) {
+		$epoch_max = $skip_epoch;
+	}
+	$self->git_init($epoch_max >= 0 ? $epoch_max : 0);
 	$self->done;
 }
 
@@ -81,6 +125,25 @@ sub init_inbox {
 # mimics Import::add and wraps it for v2
 sub add {
 	my ($self, $mime, $check_cb) = @_;
+	$self->{-inbox}->with_umask(sub {
+		_add($self, $mime, $check_cb)
+	});
+}
+
+# indexes a message, returns true if checkpointing is needed
+sub do_idx ($$$$$$$) {
+	my ($self, $msgref, $mime, $len, $num, $oid, $mid0) = @_;
+	$self->{over}->add_overview($mime, $len, $num, $oid, $mid0);
+	my $npart = $self->{partitions};
+	my $part = $num % $npart;
+	my $idx = idx_part($self, $part);
+	$idx->index_raw($len, $msgref, $num, $oid, $mid0, $mime);
+	my $n = $self->{transact_bytes} += $len;
+	$n >= (PublicInbox::SearchIdx::BATCH_BYTES * $npart);
+}
+
+sub _add {
+	my ($self, $mime, $check_cb) = @_;
 
 	# spam check:
 	if ($check_cb) {
@@ -101,18 +164,14 @@ sub add {
 	my $im = $self->importer;
 	my $cmt = $im->add($mime);
 	$cmt = $im->get_mark($cmt);
-	my ($oid, $len, $msgref) = @{$im->{last_object}};
+	$self->{last_commit}->[$self->{epoch_max}] = $cmt;
 
-	my $nparts = $self->{partitions};
-	my $part = $num % $nparts;
-	my $idx = $self->idx_part($part);
-	$idx->index_raw($len, $msgref, $num, $oid, $mid0, $mime);
-	my $n = $self->{transact_bytes} += $len;
-	if ($n > (PublicInbox::SearchIdx::BATCH_BYTES * $nparts)) {
+	my ($oid, $len, $msgref) = @{$im->{last_object}};
+	if (do_idx($self, $msgref, $mime, $len, $num, $oid, $mid0)) {
 		$self->checkpoint;
 	}
 
-	$mime;
+	$cmt;
 }
 
 sub num_for {
@@ -127,16 +186,28 @@ sub num_for {
 		};
 
 		# crap, Message-ID is already known, hope somebody just resent:
-		$self->barrier;
 		foreach my $m (@$mids) {
 			# read-only lookup now safe to do after above barrier
-			my $existing = $self->lookup_content($mime, $m);
+			my $existing = lookup_content($self, $mime, $m);
 			# easy, don't store duplicates
 			# note: do not add more diagnostic info here since
 			# it gets noisy on public-inbox-watch restarts
 			return if $existing;
 		}
 
+		# AltId may pre-populate article numbers (e.g. X-Mail-Count
+		# or NNTP article number), use that article number if it's
+		# not in Over.
+		my $altid = $self->{-inbox}->{altid};
+		if ($altid && grep(/:file=msgmap\.sqlite3\z/, @$altid)) {
+			my $num = $self->{mm}->num_for($mid);
+
+			if (defined $num && !$self->{over}->get_art($num)) {
+				$$mid0 = $mid;
+				return $num;
+			}
+		}
+
 		# very unlikely:
 		warn "<$mid> reused for mismatched content\n";
 
@@ -160,19 +231,19 @@ sub num_for_harder {
 
 	my $hdr = $mime->header_obj;
 	my $dig = content_digest($mime);
-	$$mid0 = PublicInbox::Import::digest2mid($dig);
+	$$mid0 = PublicInbox::Import::digest2mid($dig, $hdr);
 	my $num = $self->{mm}->mid_insert($$mid0);
 	unless (defined $num) {
 		# it's hard to spoof the last Received: header
 		my @recvd = $hdr->header_raw('Received');
 		$dig->add("Received: $_") foreach (@recvd);
-		$$mid0 = PublicInbox::Import::digest2mid($dig);
+		$$mid0 = PublicInbox::Import::digest2mid($dig, $hdr);
 		$num = $self->{mm}->mid_insert($$mid0);
 
 		# fall back to a random Message-ID and give up determinism:
 		until (defined($num)) {
 			$dig->add(rand);
-			$$mid0 = PublicInbox::Import::digest2mid($dig);
+			$$mid0 = PublicInbox::Import::digest2mid($dig, $hdr);
 			warn "using random Message-ID <$$mid0> as fallback\n";
 			$num = $self->{mm}->mid_insert($$mid0);
 		}
@@ -188,7 +259,7 @@ sub idx_part {
 
 # idempotent
 sub idx_init {
-	my ($self) = @_;
+	my ($self, $opt) = @_;
 	return if $self->{idx_parts};
 	my $ibx = $self->{-inbox};
 
@@ -197,11 +268,31 @@ sub idx_init {
 	# frequently activated.
 	delete $ibx->{$_} foreach (qw(git mm search));
 
+	my $indexlevel = $ibx->{indexlevel};
+	if ($indexlevel && $indexlevel eq 'basic') {
+		$self->{parallel} = 0;
+	}
+
+	if ($self->{parallel}) {
+		pipe(my ($r, $w)) or die "pipe failed: $!";
+		# pipe for barrier notifications doesn't need to be big,
+		# 1031: F_SETPIPE_SZ
+		fcntl($w, 1031, 4096) if $^O eq 'linux';
+		$self->{bnote} = [ $r, $w ];
+		$w->autoflush(1);
+	}
+
 	my $over = $self->{over};
 	$ibx->umask_prepare;
 	$ibx->with_umask(sub {
-		$self->lock_acquire;
-		$over->create($self);
+		$self->lock_acquire unless ($opt && $opt->{-skip_lock});
+		$over->create;
+
+		# -compact can change partition count while -watch is idle
+		my $nparts = count_partitions($self);
+		if ($nparts && $nparts != $self->{partitions}) {
+			$self->{partitions} = $nparts;
+		}
 
 		# need to create all parts before initializing msgmap FD
 		my $max = $self->{partitions} - 1;
@@ -220,180 +311,396 @@ sub idx_init {
 	});
 }
 
-sub purge_oids {
-	my ($self, $purge) = @_; # $purge = { $object_id => 1, ... }
+# returns an array mapping [ epoch => latest_commit ]
+# latest_commit may be undef if nothing was done to that epoch
+# $replace_map = { $object_id => $strref, ... }
+sub _replace_oids ($$$) {
+	my ($self, $mime, $replace_map) = @_;
 	$self->done;
 	my $pfx = "$self->{-inbox}->{mainrepo}/git";
-	my $purges = [];
-	foreach my $i (0..$self->{max_git}) {
-		my $git = PublicInbox::Git->new("$pfx/$i.git");
-		my $im = $self->import_init($git, 0);
-		$purges->[$i] = $im->purge_oids($purge);
+	my $rewrites = []; # epoch => commit
+	my $max = $self->{epoch_max};
+
+	unless (defined($max)) {
+		defined(my $latest = git_dir_latest($self, \$max)) or return;
+		$self->{epoch_max} = $max;
+	}
+
+	foreach my $i (0..$max) {
+		my $git_dir = "$pfx/$i.git";
+		-d $git_dir or next;
+		my $git = PublicInbox::Git->new($git_dir);
+		my $im = $self->import_init($git, 0, 1);
+		$rewrites->[$i] = $im->replace_oids($mime, $replace_map);
+		$im->done;
 	}
-	$purges;
+	$rewrites;
 }
 
-sub remove_internal {
-	my ($self, $mime, $cmt_msg, $purge) = @_;
-	$self->barrier;
+sub content_ids ($) {
+	my ($mime) = @_;
+	my @cids = ( content_id($mime) );
+
+	# Email::MIME->as_string doesn't always round-trip, so we may
+	# use a second content_id
+	my $rt = content_id(PublicInbox::MIME->new(\($mime->as_string)));
+	push @cids, $rt if $cids[0] ne $rt;
+	\@cids;
+}
+
+sub content_matches ($$) {
+	my ($cids, $existing) = @_;
+	my $cid = content_id($existing);
+	foreach (@$cids) {
+		return 1 if $_ eq $cid
+	}
+	0
+}
+
+# used for removing or replacing (purging)
+sub rewrite_internal ($$;$$$) {
+	my ($self, $old_mime, $cmt_msg, $new_mime, $sref) = @_;
 	$self->idx_init;
-	my $im = $self->importer unless $purge;
-	my $ibx = $self->{-inbox};
-	my $srch = $ibx->search;
-	my $cid = content_id($mime);
+	my ($im, $need_reindex, $replace_map);
+	if ($sref) {
+		$replace_map = {}; # oid => sref
+		$need_reindex = [] if $new_mime;
+	} else {
+		$im = $self->importer;
+	}
+	my $over = $self->{over};
+	my $cids = content_ids($old_mime);
 	my $parts = $self->{idx_parts};
-	my $mm = $self->{mm};
 	my $removed;
-	my $mids = mids($mime->header_obj);
+	my $mids = mids($old_mime->header_obj);
 
 	# We avoid introducing new blobs into git since the raw content
 	# can be slightly different, so we do not need the user-supplied
 	# message now that we have the mids and content_id
-	$mime = undef;
+	$old_mime = undef;
+	my $mark;
 
 	foreach my $mid (@$mids) {
-		$srch->reopen->each_smsg_by_mid($mid, sub {
-			my ($smsg) = @_;
-			$smsg->load_expand;
-			my $msg = $ibx->msg_by_smsg($smsg);
+		my %gone; # num => [ smsg, raw ]
+		my ($id, $prev);
+		while (my $smsg = $over->next_by_mid($mid, \$id, \$prev)) {
+			my $msg = get_blob($self, $smsg);
 			if (!defined($msg)) {
 				warn "broken smsg for $mid\n";
-				return 1; # continue
+				next; # continue
 			}
 			my $orig = $$msg;
 			my $cur = PublicInbox::MIME->new($msg);
-			if (content_id($cur) eq $cid) {
-				$mm->num_delete($smsg->num);
-				# $removed should only be set once assuming
-				# no bugs in our deduplication code:
-				$removed = $smsg;
-				$removed->{mime} = $cur;
-				my $oid = $smsg->{blob};
-				if ($purge) {
-					$purge->{$oid} = 1;
-				} else {
-					$im->remove(\$orig, $cmt_msg);
-				}
-				$orig = undef;
-				$removed->num; # memoize this for callers
-
-				foreach my $idx (@$parts) {
-					$idx->remote_remove($oid, $mid);
-				}
-				$self->{over}->remove_oid($oid, $mid);
+			if (content_matches($cids, $cur)) {
+				$smsg->{mime} = $cur;
+				$gone{$smsg->{num}} = [ $smsg, \$orig ];
 			}
-			1; # continue
-		});
-		$self->barrier;
+		}
+		my $n = scalar keys %gone;
+		next unless $n;
+		if ($n > 1) {
+			warn "BUG: multiple articles linked to <$mid>\n",
+				join(',', sort keys %gone), "\n";
+		}
+		foreach my $num (keys %gone) {
+			my ($smsg, $orig) = @{$gone{$num}};
+			# $removed should only be set once assuming
+			# no bugs in our deduplication code:
+			$removed = $smsg;
+			my $oid = $smsg->{blob};
+			if ($replace_map) {
+				$replace_map->{$oid} = $sref;
+			} else {
+				($mark, undef) = $im->remove($orig, $cmt_msg);
+			}
+			$orig = undef;
+			if ($need_reindex) { # ->replace
+				push @$need_reindex, $smsg;
+			} else { # ->purge or ->remove
+				$self->{mm}->num_delete($num);
+			}
+			unindex_oid_remote($self, $oid, $mid);
+		}
+	}
+
+	if (defined $mark) {
+		my $cmt = $im->get_mark($mark);
+		$self->{last_commit}->[$self->{epoch_max}] = $cmt;
 	}
-	if ($purge && scalar keys %$purge) {
-		return purge_oids($self, $purge);
+	if ($replace_map && scalar keys %$replace_map) {
+		my $rewrites = _replace_oids($self, $new_mime, $replace_map);
+		return { rewrites => $rewrites, need_reindex => $need_reindex };
 	}
 	$removed;
 }
 
+# public
 sub remove {
 	my ($self, $mime, $cmt_msg) = @_;
-	remove_internal($self, $mime, $cmt_msg);
+	$self->{-inbox}->with_umask(sub {
+		rewrite_internal($self, $mime, $cmt_msg);
+	});
 }
 
+sub _replace ($$;$$) {
+	my ($self, $old_mime, $new_mime, $sref) = @_;
+	my $rewritten = $self->{-inbox}->with_umask(sub {
+		rewrite_internal($self, $old_mime, undef, $new_mime, $sref);
+	}) or return;
+
+	my $rewrites = $rewritten->{rewrites};
+	# ->done is called if there are rewrites since we gc+prune from git
+	$self->idx_init if @$rewrites;
+
+	for my $i (0..$#$rewrites) {
+		defined(my $cmt = $rewrites->[$i]) or next;
+		$self->{last_commit}->[$i] = $cmt;
+	}
+	$rewritten;
+}
+
+# public
 sub purge {
 	my ($self, $mime) = @_;
-	remove_internal($self, $mime, undef, {});
+	my $rewritten = _replace($self, $mime, undef, \'') or return;
+	$rewritten->{rewrites}
 }
 
+# returns the git object_id of $fh, does not write the object to FS
+sub git_hash_raw ($$) {
+	my ($self, $raw) = @_;
+	# grab the expected OID we have to reindex:
+	open my $tmp_fh, '+>', undef or die "failed to open tmp: $!";
+	$tmp_fh->autoflush(1);
+	print $tmp_fh $$raw or die "print \$tmp_fh: $!";
+	sysseek($tmp_fh, 0, 0) or die "seek failed: $!";
+
+	my ($r, $w);
+	pipe($r, $w) or die "failed to create pipe: $!";
+	my $rdr = { 0 => fileno($tmp_fh), 1 => fileno($w) };
+	my $git_dir = $self->{-inbox}->git->{git_dir};
+	my $cmd = ['git', "--git-dir=$git_dir", qw(hash-object --stdin)];
+	my $pid = spawn($cmd, undef, $rdr);
+	close $w;
+	local $/ = "\n";
+	chomp(my $oid = <$r>);
+	waitpid($pid, 0) == $pid or die "git hash-object did not finish";
+	die "git hash-object failed: $?" if $?;
+	$oid =~ /\A[a-f0-9]{40}\z/ or die "OID not expected: $oid";
+	$oid;
+}
 
-sub done {
-	my ($self) = @_;
-	my $im = delete $self->{im};
-	$im->done if $im; # PublicInbox::Import::done
+sub _check_mids_match ($$$) {
+	my ($old_list, $new_list, $hdrs) = @_;
+	my %old_mids = map { $_ => 1 } @$old_list;
+	my %new_mids = map { $_ => 1 } @$new_list;
+	my @old = keys %old_mids;
+	my @new = keys %new_mids;
+	my $err = "$hdrs may not be changed when replacing\n";
+	die $err if scalar(@old) != scalar(@new);
+	delete @new_mids{@old};
+	delete @old_mids{@new};
+	die $err if (scalar(keys %old_mids) || scalar(keys %new_mids));
+}
+
+# Changing Message-IDs or References with ->replace isn't supported.
+# The rules for dealing with messages with multiple or conflicting
+# Message-IDs are pretty complex and rethreading hasn't been fully
+# implemented, yet.
+sub check_mids_match ($$) {
+	my ($old_mime, $new_mime) = @_;
+	my $old = $old_mime->header_obj;
+	my $new = $new_mime->header_obj;
+	_check_mids_match(mids($old), mids($new), 'Message-ID(s)');
+	_check_mids_match(references($old), references($new),
+			'References/In-Reply-To');
+}
+
+# public
+sub replace ($$$) {
+	my ($self, $old_mime, $new_mime) = @_;
+
+	check_mids_match($old_mime, $new_mime);
+
+	# mutt will always add Content-Length:, Status:, Lines: when editing
+	PublicInbox::Import::drop_unwanted_headers($new_mime);
+
+	my $raw = $new_mime->as_string;
+	my $expect_oid = git_hash_raw($self, \$raw);
+	my $rewritten = _replace($self, $old_mime, $new_mime, \$raw) or return;
+	my $need_reindex = $rewritten->{need_reindex};
+
+	# just in case we have bugs in deduplication code:
+	my $n = scalar(@$need_reindex);
+	if ($n > 1) {
+		my $list = join(', ', map {
+					"$_->{num}: <$_->{mid}>"
+				} @$need_reindex);
+		warn <<"";
+W: rewritten $n messages matching content of original message (expected: 1).
+W: possible bug in public-inbox, NNTP article IDs and Message-IDs follow:
+W: $list
 
-	if (my $mm = delete $self->{mm}) {
-		$mm->{dbh}->commit;
 	}
 
-	# order matters, we can only close {over} after all partitions
-	# are done because the partitions also write to {over}
-	my $parts = delete $self->{idx_parts};
-	if ($parts) {
-		$_->remote_commit for @$parts;
-		$_->remote_close for @$parts;
+	# make sure we really got the OID:
+	my ($oid, $type, $len) = $self->{-inbox}->git->check($expect_oid);
+	$oid eq $expect_oid or die "BUG: $expect_oid not found after replace";
+
+	# don't leak FDs to Xapian:
+	$self->{-inbox}->git->cleanup;
+
+	# reindex modified messages:
+	for my $smsg (@$need_reindex) {
+		my $num = $smsg->{num};
+		my $mid0 = $smsg->{mid};
+		do_idx($self, \$raw, $new_mime, $len, $num, $oid, $mid0);
 	}
+	$rewritten->{rewrites};
+}
 
-	my $over = $self->{over};
-	$over->remote_commit;
-	$over->remote_close;
-	$self->{transact_bytes} = 0;
-	$self->lock_release if $parts;
+sub last_commit_part ($$;$) {
+	my ($self, $i, $cmt) = @_;
+	my $v = PublicInbox::Search::SCHEMA_VERSION();
+	$self->{mm}->last_commit_xap($v, $i, $cmt);
 }
 
-sub checkpoint {
+sub set_last_commits ($) {
 	my ($self) = @_;
-	my $im = $self->{im};
-	$im->checkpoint if $im; # PublicInbox::Import::checkpoint
-	$self->barrier(1);
+	defined(my $epoch_max = $self->{epoch_max}) or return;
+	my $last_commit = $self->{last_commit};
+	foreach my $i (0..$epoch_max) {
+		defined(my $cmt = $last_commit->[$i]) or next;
+		$last_commit->[$i] = undef;
+		last_commit_part($self, $i, $cmt);
+	}
 }
 
-# issue a write barrier to ensure all data is visible to other processes
-# and read-only ops.  Order of data importance is: git > SQLite > Xapian
-sub barrier {
-	my ($self, $fsync) = @_;
+sub barrier_init {
+	my ($self, $n) = @_;
+	$self->{bnote} or return;
+	--$n;
+	my $barrier = { map { $_ => 1 } (0..$n) };
+}
+
+sub barrier_wait {
+	my ($self, $barrier) = @_;
+	my $bnote = $self->{bnote} or return;
+	my $r = $bnote->[0];
+	while (scalar keys %$barrier) {
+		defined(my $l = $r->getline) or die "EOF on barrier_wait: $!";
+		$l =~ /\Abarrier (\d+)/ or die "bad line on barrier_wait: $l";
+		delete $barrier->{$1} or die "bad part[$1] on barrier wait";
+	}
+}
+
+# public
+sub checkpoint ($;$) {
+	my ($self, $wait) = @_;
 
 	if (my $im = $self->{im}) {
-		$im->barrier;
+		if ($wait) {
+			$im->barrier;
+		} else {
+			$im->checkpoint;
+		}
 	}
 	my $parts = $self->{idx_parts};
 	if ($parts) {
 		my $dbh = $self->{mm}->{dbh};
-		$dbh->commit; # SQLite msgmap data is second in importance
 
-		my $over = $self->{over};
+		# SQLite msgmap data is second in importance
+		$dbh->commit;
+
+		# SQLite overview is third
+		$self->{over}->commit_lazy;
+
+		# Now deal with Xapian
+		if ($wait) {
+			my $barrier = $self->barrier_init(scalar @$parts);
 
-		# Now deal with Xapian and overview DB
-		$over->barrier_init(scalar(@$parts));
+			# each partition needs to issue a barrier command
+			$_->remote_barrier for @$parts;
 
-		# each partition needs to issue a barrier command to over
-		$_->remote_barrier foreach @$parts;
+			# wait for each Xapian partition
+			$self->barrier_wait($barrier);
+		} else {
+			$_->remote_commit for @$parts;
+		}
 
-		$over->barrier_wait; # wait for each Xapian partition
-		$over->commit_fsync if $fsync;
+		# last_commit is special, don't commit these until
+		# remote partitions are done:
+		$dbh->begin_work;
+		set_last_commits($self);
+		$dbh->commit;
 
 		$dbh->begin_work;
 	}
 	$self->{transact_bytes} = 0;
 }
 
-sub git_init {
-	my ($self, $new) = @_;
-	my $pfx = "$self->{-inbox}->{mainrepo}/git";
-	my $git_dir = "$pfx/$new.git";
-	my @cmd = (qw(git init --bare -q), $git_dir);
-	PublicInbox::Import::run_die(\@cmd);
+# issue a write barrier to ensure all data is visible to other processes
+# and read-only ops.  Order of data importance is: git > SQLite > Xapian
+# public
+sub barrier { checkpoint($_[0], 1) };
 
+# public
+sub done {
+	my ($self) = @_;
+	my $im = delete $self->{im};
+	$im->done if $im; # PublicInbox::Import::done
+	checkpoint($self);
+	my $mm = delete $self->{mm};
+	$mm->{dbh}->commit if $mm;
+	my $parts = delete $self->{idx_parts};
+	if ($parts) {
+		$_->remote_close for @$parts;
+	}
+	$self->{over}->disconnect;
+	delete $self->{bnote};
+	$self->{transact_bytes} = 0;
+	$self->lock_release if $parts;
+	$self->{-inbox}->git->cleanup;
+}
+
+sub fill_alternates ($$) {
+	my ($self, $epoch) = @_;
+
+	my $pfx = "$self->{-inbox}->{mainrepo}/git";
 	my $all = "$self->{-inbox}->{mainrepo}/all.git";
+	my @cmd;
 	unless (-d $all) {
-		@cmd = (qw(git init --bare -q), $all);
-		PublicInbox::Import::run_die(\@cmd);
-		@cmd = (qw/git config/, "--file=$all/config",
-				'repack.writeBitmaps', 'true');
-		PublicInbox::Import::run_die(\@cmd);
+		PublicInbox::Import::init_bare($all);
 	}
-
-	@cmd = (qw/git config/, "--file=$git_dir/config",
+	@cmd = (qw/git config/, "--file=$pfx/$epoch.git/config",
 			'include.path', '../../all.git/config');
 	PublicInbox::Import::run_die(\@cmd);
 
 	my $alt = "$all/objects/info/alternates";
-	my $new_obj_dir = "../../git/$new.git/objects";
 	my %alts;
+	my @add;
 	if (-e $alt) {
 		open(my $fh, '<', $alt) or die "open < $alt: $!\n";
 		%alts = map { chomp; $_ => 1 } (<$fh>);
 	}
-	return $git_dir if $alts{$new_obj_dir};
+	foreach my $i (0..$epoch) {
+		my $dir = "../../git/$i.git/objects";
+		push @add, $dir if !$alts{$dir} && -d "$pfx/$i.git";
+	}
+	return unless @add;
 	open my $fh, '>>', $alt or die "open >> $alt: $!\n";
-	print $fh "$new_obj_dir\n" or die "print >> $alt: $!\n";
+	foreach my $dir (@add) {
+		print $fh "$dir\n" or die "print >> $alt: $!\n";
+	}
 	close $fh or die "close $alt: $!\n";
+}
+
+sub git_init {
+	my ($self, $epoch) = @_;
+	my $git_dir = "$self->{-inbox}->{mainrepo}/git/$epoch.git";
+	my @cmd = (qw(git init --bare -q), $git_dir);
+	PublicInbox::Import::run_die(\@cmd);
+	fill_alternates($self, $epoch);
 	$git_dir
 }
 
@@ -405,7 +712,7 @@ sub git_dir_latest {
 	my $latest;
 	opendir my $dh, $pfx or die "opendir $pfx: $!\n";
 	while (defined(my $git_dir = readdir($dh))) {
-		$git_dir =~ m!\A(\d+)\.git\z! or next;
+		$git_dir =~ m!\A([0-9]+)\.git\z! or next;
 		if ($1 > $$max) {
 			$$max = $1;
 			$latest = "$pfx/$git_dir";
@@ -423,46 +730,48 @@ sub importer {
 		} else {
 			$self->{im} = undef;
 			$im->done;
-			$self->barrier(1);
 			$im = undef;
-			my $git_dir = $self->git_init(++$self->{max_git});
+			$self->checkpoint;
+			my $git_dir = $self->git_init(++$self->{epoch_max});
 			my $git = PublicInbox::Git->new($git_dir);
 			return $self->import_init($git, 0);
 		}
 	}
-	my $new = 0;
+	my $epoch = 0;
 	my $max;
 	my $latest = git_dir_latest($self, \$max);
 	if (defined $latest) {
 		my $git = PublicInbox::Git->new($latest);
 		my $packed_bytes = $git->packed_bytes;
-		if ($packed_bytes >= $self->{rotate_bytes}) {
-			$new = $max + 1;
+		my $unpacked_bytes = $packed_bytes / $PACKING_FACTOR;
+
+		if ($unpacked_bytes >= $self->{rotate_bytes}) {
+			$epoch = $max + 1;
 		} else {
-			$self->{max_git} = $max;
+			$self->{epoch_max} = $max;
 			return $self->import_init($git, $packed_bytes);
 		}
 	}
-	$self->{max_git} = $new;
-	$latest = $self->git_init($new);
+	$self->{epoch_max} = $epoch;
+	$latest = $self->git_init($epoch);
 	$self->import_init(PublicInbox::Git->new($latest), 0);
 }
 
 sub import_init {
-	my ($self, $git, $packed_bytes) = @_;
+	my ($self, $git, $packed_bytes, $tmp) = @_;
 	my $im = PublicInbox::Import->new($git, undef, undef, $self->{-inbox});
 	$im->{bytes_added} = int($packed_bytes / $PACKING_FACTOR);
 	$im->{want_object_info} = 1;
 	$im->{lock_path} = undef;
 	$im->{path_type} = 'v2';
-	$self->{im} = $im;
+	$self->{im} = $im unless $tmp;
+	$im;
 }
 
 # XXX experimental
 sub diff ($$$) {
 	my ($mid, $cur, $new) = @_;
 	use File::Temp qw(tempfile);
-	use PublicInbox::Spawn qw(spawn);
 
 	my ($ah, $an) = tempfile('email-cur-XXXXXXXX', TMPDIR => 1);
 	print $ah $cur->as_string or die "print: $!";
@@ -479,34 +788,39 @@ sub diff ($$$) {
 	unlink($an, $bn);
 }
 
-sub lookup_content {
-	my ($self, $mime, $mid) = @_;
+sub get_blob ($$) {
+	my ($self, $smsg) = @_;
+	if (my $im = $self->{im}) {
+		my $msg = $im->cat_blob($smsg->{blob});
+		return $msg if $msg;
+	}
+	# older message, should be in alternates
 	my $ibx = $self->{-inbox};
+	$ibx->msg_by_smsg($smsg);
+}
 
-	my $srch = $ibx->search->reopen;
-	my $cid = content_id($mime);
-	my $found;
-	$srch->each_smsg_by_mid($mid, sub {
-		my ($smsg) = @_;
-		$smsg->load_expand;
-		my $msg = $ibx->msg_by_smsg($smsg);
+sub lookup_content ($$$) {
+	my ($self, $mime, $mid) = @_;
+	my $over = $self->{over};
+	my $cids = content_ids($mime);
+	my ($id, $prev);
+	while (my $smsg = $over->next_by_mid($mid, \$id, \$prev)) {
+		my $msg = get_blob($self, $smsg);
 		if (!defined($msg)) {
 			warn "broken smsg for $mid\n";
-			return 1; # continue
+			next;
 		}
 		my $cur = PublicInbox::MIME->new($msg);
-		if (content_id($cur) eq $cid) {
+		if (content_matches($cids, $cur)) {
 			$smsg->{mime} = $cur;
-			$found = $smsg;
-			return 0; # break out of loop
+			return $smsg;
 		}
 
+
 		# XXX DEBUG_DIFF is experimental and may be removed
 		diff($mid, $cur, $mime) if $ENV{DEBUG_DIFF};
-
-		1; # continue
-	});
-	$found;
+	}
+	undef;
 }
 
 sub atfork_child {
@@ -520,21 +834,23 @@ sub atfork_child {
 		$im->atfork_child;
 	}
 	die "unexpected mm" if $self->{mm};
+	close $self->{bnote}->[0] or die "close bnote[0]: $!\n";
+	$self->{bnote}->[1];
 }
 
-sub mark_deleted {
-	my ($self, $D, $git, $oid) = @_;
+sub mark_deleted ($$$$) {
+	my ($self, $sync, $git, $oid) = @_;
 	my $msgref = $git->cat_file($oid);
 	my $mime = PublicInbox::MIME->new($$msgref);
 	my $mids = mids($mime->header_obj);
 	my $cid = content_id($mime);
 	foreach my $mid (@$mids) {
-		$D->{"$mid\0$cid"} = 1;
+		$sync->{D}->{"$mid\0$cid"} = $oid;
 	}
 }
 
-sub reindex_oid {
-	my ($self, $mm_tmp, $D, $git, $oid, $regen) = @_;
+sub reindex_oid ($$$$) {
+	my ($self, $sync, $git, $oid) = @_;
 	my $len;
 	my $msgref = $git->cat_file($oid, \$len);
 	my $mime = PublicInbox::MIME->new($$msgref);
@@ -542,20 +858,21 @@ sub reindex_oid {
 	my $cid = content_id($mime);
 
 	# get the NNTP article number we used before, highest number wins
-	# and gets deleted from mm_tmp;
+	# and gets deleted from sync->{mm_tmp};
 	my $mid0;
 	my $num = -1;
 	my $del = 0;
 	foreach my $mid (@$mids) {
-		$del += (delete $D->{"$mid\0$cid"} || 0);
-		my $n = $mm_tmp->num_for($mid);
+		$del += delete($sync->{D}->{"$mid\0$cid"}) ? 1 : 0;
+		my $n = $sync->{mm_tmp}->num_for($mid);
 		if (defined $n && $n > $num) {
 			$mid0 = $mid;
 			$num = $n;
+			$self->{mm}->mid_set($num, $mid0);
 		}
 	}
-	if (!defined($mid0) && $regen && !$del) {
-		$num = $$regen--;
+	if (!defined($mid0) && !$del) {
+		$num = $sync->{regen}--;
 		die "BUG: ran out of article numbers\n" if $num <= 0;
 		my $mm = $self->{mm};
 		foreach my $mid (reverse @$mids) {
@@ -576,7 +893,8 @@ sub reindex_oid {
 
 	if (!defined($mid0) || $del) {
 		if (!defined($mid0) && $del) { # expected for deletes
-			$$regen--;
+			$num = $sync->{regen}--;
+			$self->{mm}->num_highwater($num) if !$sync->{reindex};
 			return
 		}
 
@@ -590,110 +908,309 @@ sub reindex_oid {
 		return;
 
 	}
-	$mm_tmp->mid_delete($mid0) or
+	$sync->{mm_tmp}->mid_delete($mid0) or
 		die "failed to delete <$mid0> for article #$num\n";
-
-	my $nparts = $self->{partitions};
-	my $part = $num % $nparts;
-	my $idx = $self->idx_part($part);
-	$idx->index_raw($len, $msgref, $num, $oid, $mid0, $mime);
-	my $n = $self->{transact_bytes} += $len;
-	if ($n > (PublicInbox::SearchIdx::BATCH_BYTES * $nparts)) {
+	$sync->{nr}++;
+	if (do_idx($self, $msgref, $mime, $len, $num, $oid, $mid0)) {
 		$git->cleanup;
-		$mm_tmp->atfork_prepare;
+		$sync->{mm_tmp}->atfork_prepare;
 		$self->done; # release lock
+
+		if (my $pr = $sync->{-opt}->{-progress}) {
+			my ($bn) = (split('/', $git->{git_dir}))[-1];
+			$pr->("$bn ".sprintf($sync->{-regen_fmt}, $sync->{nr}));
+		}
+
 		# allow -watch or -mda to write...
 		$self->idx_init; # reacquire lock
-		$mm_tmp->atfork_parent;
+		$sync->{mm_tmp}->atfork_parent;
 	}
 }
 
-sub reindex {
-	my ($self, $regen) = @_;
-	my $ibx = $self->{-inbox};
-	my $pfx = "$ibx->{mainrepo}/git";
-	my $max_git;
-	my $latest = git_dir_latest($self, \$max_git);
-	return unless defined $latest;
-	my $head = $ibx->{ref_head} || 'refs/heads/master';
-	$self->idx_init; # acquire lock
-	my $x40 = qr/[a-f0-9]{40}/;
-	my $mm_tmp = $self->{mm}->tmp_clone;
-	if (!$regen) {
-		my (undef, $max) = $mm_tmp->minmax;
-		unless (defined $max) {
-			$regen = 1;
-			warn
-"empty msgmap.sqlite3, regenerating article numbers\n";
-		}
-	}
-	my $tip; # latest commit out of all git repos
-	if ($regen) {
-		my $regen_max = 0;
-		for (my $cur = $max_git; $cur >= 0; $cur--) {
-			die "already reindexing!\n" if $self->{reindex_pipe};
-			my $git = PublicInbox::Git->new("$pfx/$cur.git");
-			-d $git->{git_dir} or next; # missing parts are fine
-			chomp($tip = $git->qx('rev-parse', $head)) unless $tip;
-			my $h = $cur == $max_git ? $tip : $head;
-
-			# can't use 'rev-list --count' if we use --diff-filter
-			my $fh = $git->popen(qw(log --pretty=tformat:%h
-					--no-notes --no-color --no-renames
-					--diff-filter=AM), $h, '--', 'm');
-			++$regen_max while <$fh>;
-		}
-		die "No messages found in $pfx/*.git, bug?\n" unless $regen_max;
-		$regen = \$regen_max;
-	}
-	my $D = {};
-	my @cmd = qw(log --raw -r --pretty=tformat:%h
-			--no-notes --no-color --no-abbrev --no-renames);
+# only update last_commit for $i on reindex iff newer than current
+sub update_last_commit ($$$$) {
+	my ($self, $git, $i, $cmt) = @_;
+	my $last = last_commit_part($self, $i);
+	if (defined $last && is_ancestor($git, $last, $cmt)) {
+		my @cmd = (qw(rev-list --count), "$last..$cmt");
+		chomp(my $n = $git->qx(@cmd));
+		return if $n ne '' && $n == 0;
+	}
+	last_commit_part($self, $i, $cmt);
+}
 
-	# if we are regenerating, we must not use a newer tip commit than what
-	# the regeneration counter used:
-	$tip ||= $head;
+sub git_dir_n ($$) { "$_[0]->{-inbox}->{mainrepo}/git/$_[1].git" }
 
-	# work backwards through history
-	for (my $cur = $max_git; $cur >= 0; $cur--) {
-		die "already reindexing!\n" if delete $self->{reindex_pipe};
-		my $cmt;
-		my $git_dir = "$pfx/$cur.git";
+sub last_commits ($$) {
+	my ($self, $epoch_max) = @_;
+	my $heads = [];
+	for (my $i = $epoch_max; $i >= 0; $i--) {
+		$heads->[$i] = last_commit_part($self, $i);
+	}
+	$heads;
+}
+
+*is_ancestor = *PublicInbox::SearchIdx::is_ancestor;
+
+# returns a revision range for git-log(1)
+sub log_range ($$$$$) {
+	my ($self, $sync, $git, $i, $tip) = @_;
+	my $opt = $sync->{-opt};
+	my $pr = $opt->{-progress} if (($opt->{verbose} || 0) > 1);
+	my $cur = $sync->{ranges}->[$i] or do {
+		$pr->("$i.git indexing all of $tip") if $pr;
+		return $tip; # all of it
+	};
+
+	# fast equality check to avoid (v)fork+execve overhead
+	if ($cur eq $tip) {
+		$sync->{ranges}->[$i] = undef;
+		return;
+	}
+
+	my $range = "$cur..$tip";
+	$pr->("$i.git checking contiguity... ") if $pr;
+	if (is_ancestor($git, $cur, $tip)) { # common case
+		$pr->("OK\n") if $pr;
+		my $n = $git->qx(qw(rev-list --count), $range);
+		chomp($n);
+		if ($n == 0) {
+			$sync->{ranges}->[$i] = undef;
+			$pr->("$i.git has nothing new\n") if $pr;
+			return; # nothing to do
+		}
+		$pr->("$i.git has $n changes since $cur\n") if $pr;
+	} else {
+		$pr->("FAIL\n") if $pr;
+		warn <<"";
+discontiguous range: $range
+Rewritten history? (in $git->{git_dir})
+
+		chomp(my $base = $git->qx('merge-base', $tip, $cur));
+		if ($base) {
+			$range = "$base..$tip";
+			warn "found merge-base: $base\n"
+		} else {
+			$range = $tip;
+			warn "discarding history at $cur\n";
+		}
+		warn <<"";
+reindexing $git->{git_dir} starting at
+$range
+
+		$sync->{unindex_range}->{$i} = "$base..$cur";
+	}
+	$range;
+}
+
+sub sync_prepare ($$$) {
+	my ($self, $sync, $epoch_max) = @_;
+	my $pr = $sync->{-opt}->{-progress};
+	my $regen_max = 0;
+	my $head = $self->{-inbox}->{ref_head} || 'refs/heads/master';
+
+	# reindex stops at the current heads and we later rerun index_sync
+	# without {reindex}
+	my $reindex_heads = last_commits($self, $epoch_max) if $sync->{reindex};
+
+	for (my $i = $epoch_max; $i >= 0; $i--) {
+		die 'BUG: already indexing!' if $self->{reindex_pipe};
+		my $git_dir = git_dir_n($self, $i);
 		-d $git_dir or next; # missing parts are fine
 		my $git = PublicInbox::Git->new($git_dir);
-		my $h = $cur == $max_git ? $tip : $head;
-		my $fh = $self->{reindex_pipe} = $git->popen(@cmd, $h);
-		while (<$fh>) {
-			if (/\A$x40$/o) {
-				chomp($cmt = $_);
-			} elsif (/\A:\d{6} 100644 $x40 ($x40) [AM]\tm$/o) {
-				$self->reindex_oid($mm_tmp, $D, $git, $1,
-						$regen);
-			} elsif (/\A:\d{6} 100644 $x40 ($x40) [AM]\td$/o) {
-				$self->mark_deleted($D, $git, $1);
-			}
+		if ($reindex_heads) {
+			$head = $reindex_heads->[$i] or next;
+		}
+		chomp(my $tip = $git->qx(qw(rev-parse -q --verify), $head));
+
+		next if $?; # new repo
+		my $range = log_range($self, $sync, $git, $i, $tip) or next;
+		$sync->{ranges}->[$i] = $range;
+
+		# can't use 'rev-list --count' if we use --diff-filter
+		$pr->("$i.git counting $range ... ") if $pr;
+		my $n = 0;
+		my $fh = $git->popen(qw(log --pretty=tformat:%H
+				--no-notes --no-color --no-renames
+				--diff-filter=AM), $range, '--', 'm');
+		++$n while <$fh>;
+		$pr->("$n\n") if $pr;
+		$regen_max += $n;
+	}
+
+	return 0 if (!$regen_max && !keys(%{$self->{unindex_range}}));
+
+	# reindex should NOT see new commits anymore, if we do,
+	# it's a problem and we need to notice it via die()
+	my $pad = length($regen_max) + 1;
+	$sync->{-regen_fmt} = "% ${pad}u/$regen_max\n";
+	$sync->{nr} = 0;
+	return -1 if $sync->{reindex};
+	$regen_max + $self->{mm}->num_highwater() || 0;
+}
+
+sub unindex_oid_remote ($$$) {
+	my ($self, $oid, $mid) = @_;
+	$_->remote_remove($oid, $mid) foreach @{$self->{idx_parts}};
+	$self->{over}->remove_oid($oid, $mid);
+}
+
+sub unindex_oid ($$$) {
+	my ($self, $git, $oid) = @_;
+	my $msgref = $git->cat_file($oid);
+	my $mime = PublicInbox::MIME->new($msgref);
+	my $mids = mids($mime->header_obj);
+	$mime = $msgref = undef;
+	my $over = $self->{over};
+	foreach my $mid (@$mids) {
+		my %gone;
+		my ($id, $prev);
+		while (my $smsg = $over->next_by_mid($mid, \$id, \$prev)) {
+			$gone{$smsg->{num}} = 1 if $oid eq $smsg->{blob};
+			1; # continue
+		}
+		my $n = scalar keys %gone;
+		next unless $n;
+		if ($n > 1) {
+			warn "BUG: multiple articles linked to $oid\n",
+				join(',',sort keys %gone), "\n";
 		}
-		delete $self->{reindex_pipe};
+		foreach my $num (keys %gone) {
+			$self->{unindexed}->{$_}++;
+			$self->{mm}->num_delete($num);
+		}
+		unindex_oid_remote($self, $oid, $mid);
+	}
+}
+
+my $x40 = qr/[a-f0-9]{40}/;
+sub unindex ($$$$) {
+	my ($self, $sync, $git, $unindex_range) = @_;
+	my $un = $self->{unindexed} ||= {}; # num => removal count
+	my $before = scalar keys %$un;
+	my @cmd = qw(log --raw -r
+			--no-notes --no-color --no-abbrev --no-renames);
+	my $fh = $self->{reindex_pipe} = $git->popen(@cmd, $unindex_range);
+	while (<$fh>) {
+		/\A:\d{6} 100644 $x40 ($x40) [AM]\tm$/o or next;
+		unindex_oid($self, $git, $1);
 	}
-	my $gaps;
-	if ($regen && $$regen != 0) {
-		warn "W: leftover article number ($$regen)\n";
-		$gaps = 1;
+	delete $self->{reindex_pipe};
+	$fh = undef;
+
+	return unless $sync->{-opt}->{prune};
+	my $after = scalar keys %$un;
+	return if $before == $after;
+
+	# ensure any blob can not longer be accessed via dumb HTTP
+	PublicInbox::Import::run_die(['git', "--git-dir=$git->{git_dir}",
+		qw(-c gc.reflogExpire=now gc --prune=all)]);
+}
+
+sub sync_ranges ($$$) {
+	my ($self, $sync, $epoch_max) = @_;
+	my $reindex = $sync->{reindex};
+
+	return last_commits($self, $epoch_max) unless $reindex;
+	return [] if ref($reindex) ne 'HASH';
+
+	my $ranges = $reindex->{from}; # arrayref;
+	if (ref($ranges) ne 'ARRAY') {
+		die 'BUG: $reindex->{from} not an ARRAY';
 	}
-	my ($min, $max) = $mm_tmp->minmax;
-	if (defined $max) {
-		warn "W: leftover article numbers at $min..$max\n";
-		$gaps = 1;
+	$ranges;
+}
+
+sub index_epoch ($$$) {
+	my ($self, $sync, $i) = @_;
+
+	my $git_dir = git_dir_n($self, $i);
+	die 'BUG: already reindexing!' if $self->{reindex_pipe};
+	-d $git_dir or return; # missing parts are fine
+	fill_alternates($self, $i);
+	my $git = PublicInbox::Git->new($git_dir);
+	if (my $unindex_range = delete $sync->{unindex_range}->{$i}) {
+		unindex($self, $sync, $git, $unindex_range);
+	}
+	defined(my $range = $sync->{ranges}->[$i]) or return;
+	if (my $pr = $sync->{-opt}->{-progress}) {
+		$pr->("$i.git indexing $range\n");
 	}
-	warn "W: were old git partitions deleted?\n" if $gaps;
-	my @d = sort keys %$D;
-	if (@d) {
-		warn "BUG: ", scalar(@d)," unseen deleted messages marked\n";
-		foreach (@d) {
-			my ($mid, undef) = split(/\0/, $_, 2);
-			warn "<$mid>\n";
+
+	my @cmd = qw(log --raw -r --pretty=tformat:%H
+			--no-notes --no-color --no-abbrev --no-renames);
+	my $fh = $self->{reindex_pipe} = $git->popen(@cmd, $range);
+	my $cmt;
+	while (<$fh>) {
+		chomp;
+		$self->{current_info} = "$i.git $_";
+		if (/\A$x40$/o && !defined($cmt)) {
+			$cmt = $_;
+		} elsif (/\A:\d{6} 100644 $x40 ($x40) [AM]\tm$/o) {
+			reindex_oid($self, $sync, $git, $1);
+		} elsif (/\A:\d{6} 100644 $x40 ($x40) [AM]\td$/o) {
+			mark_deleted($self, $sync, $git, $1);
 		}
 	}
+	$fh = undef;
+	delete $self->{reindex_pipe};
+	update_last_commit($self, $git, $i, $cmt) if defined $cmt;
+}
+
+# public, called by public-inbox-index
+sub index_sync {
+	my ($self, $opt) = @_;
+	$opt ||= {};
+	my $pr = $opt->{-progress};
+	my $epoch_max;
+	my $latest = git_dir_latest($self, \$epoch_max);
+	return unless defined $latest;
+	$self->idx_init($opt); # acquire lock
+	my $sync = {
+		D => {}, # "$mid\0$cid" => $oid
+		unindex_range => {}, # EPOCH => oid_old..oid_new
+		reindex => $opt->{reindex},
+		-opt => $opt
+	};
+	$sync->{ranges} = sync_ranges($self, $sync, $epoch_max);
+	$sync->{regen} = sync_prepare($self, $sync, $epoch_max);
+
+	if ($sync->{regen}) {
+		# tmp_clone seems to fail if inside a transaction, so
+		# we rollback here (because we opened {mm} for reading)
+		# Note: we do NOT rely on DBI transactions for atomicity;
+		# only for batch performance.
+		$self->{mm}->{dbh}->rollback;
+		$self->{mm}->{dbh}->begin_work;
+		$sync->{mm_tmp} = $self->{mm}->tmp_clone;
+	}
+
+	# work backwards through history
+	for (my $i = $epoch_max; $i >= 0; $i--) {
+		index_epoch($self, $sync, $i);
+	}
+
+	# unindex is required for leftovers if "deletes" affect messages
+	# in a previous fetch+index window:
+	if (my @leftovers = values %{delete $sync->{D}}) {
+		my $git = $self->{-inbox}->git;
+		unindex_oid($self, $git, $_) for @leftovers;
+		$git->cleanup;
+	}
+	$self->done;
+
+	if (my $nr = $sync->{nr}) {
+		my $pr = $sync->{-opt}->{-progress};
+		$pr->('all.git '.sprintf($sync->{-regen_fmt}, $nr)) if $pr;
+	}
+
+	# reindex does not pick up new changes, so we rerun w/o it:
+	if ($opt->{reindex}) {
+		my %again = %$opt;
+		$sync = undef;
+		delete @again{qw(reindex -skip_lock)};
+		index_sync($self, \%again);
+	}
 }
 
 1;