[PATCH 3/3] v2: fix reindex skipping NNTP article numbers

[Eric Wong <e@80x24.org>]

`public-inbox-index --reindex' could cause NNTP article number
gaps to form when it also has to deal with new,
never-before-seen commits in mirrors running off `git fetch'.

Fix this by running two distinct invocations of ->index_sync;
once to only reindex old commits, and a second time to index
new commits.

This does not appear to be a problem on v1 at the moment,
but I'll need more time to analyze this.
---
 lib/PublicInbox/V2Writable.pm | 25 ++++++++++++++++++++++++-
 t/indexlevels-mirror.t        | 25 +++++++++++++++++++++++++
 2 files changed, 49 insertions(+), 1 deletion(-)

diff --git a/lib/PublicInbox/V2Writable.pm b/lib/PublicInbox/V2Writable.pm
index cd08acd..331c4f4 100644
--- a/lib/PublicInbox/V2Writable.pm
+++ b/lib/PublicInbox/V2Writable.pm
@@ -850,11 +850,19 @@ sub index_prepare {
 	my $pr = $opts->{-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 $opts->{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);
+		if ($reindex_heads) {
+			$head = $reindex_heads->[$i] or next;
+		}
 		chomp(my $tip = $git->qx(qw(rev-parse -q --verify), $head));
 
 		next if $?; # new repo
@@ -959,7 +967,14 @@ sub index_sync {
 
 	my $high = $self->{mm}->num_highwater();
 	my $regen = $self->index_prepare($opts, $epoch_max, $ranges);
-	$$regen += $high if $high;
+	if ($opts->{reindex}) {
+		# reindex should NOT see new commits anymore, if we do,
+		# it's a problem and we need to notice it via die()
+		$$regen = -1;
+	} else {
+		$$regen += $high;
+	}
+
 	my $D = {}; # "$mid\0$cid" => $oid
 	my @cmd = qw(log --raw -r --pretty=tformat:%H
 			--no-notes --no-color --no-abbrev --no-renames);
@@ -1001,6 +1016,14 @@ sub index_sync {
 		$git->cleanup;
 	}
 	$self->done;
+
+	# reindex does not pick up new changes, so we rerun w/o it:
+	if ($opts->{reindex}) {
+		my %again = %$opts;
+		$mm_tmp = undef;
+		delete @again{qw(reindex -skip_lock)};
+		index_sync($self, \%again);
+	}
 }
 
 1;
diff --git a/t/indexlevels-mirror.t b/t/indexlevels-mirror.t
index ce138fe..1251136 100644
--- a/t/indexlevels-mirror.t
+++ b/t/indexlevels-mirror.t
@@ -105,9 +105,17 @@ sub import_index_incremental {
 	is_deeply([sort { $a cmp $b } map { $_->{mid} } @$msgs],
 		['m@1','m@2'], 'got both messages in master');
 
+	my @rw_nums = map { $_->{num} } @{$ibx->over->query_ts(0, 0)};
+	is_deeply(\@rw_nums, [1, 2], 'master has expected NNTP articles');
+
+	my @ro_nums = map { $_->{num} } @{$ro_mirror->over->query_ts(0, 0)};
+	is_deeply(\@ro_nums, [1, 2], 'mirror has expected NNTP articles');
+
 	# remove message from master
 	ok($im->remove($mime), '2nd message removed');
 	$im->done;
+	@rw_nums = map { $_->{num} } @{$ibx->over->query_ts(0, 0)};
+	is_deeply(\@rw_nums, [1], 'unindex NNTP article'.$v.$level);
 
 	if ($level ne 'basic') {
 		is(system(@xcpdb, $mirror), 0, "v$v xcpdb OK");
@@ -132,6 +140,23 @@ sub import_index_incremental {
 		($nr, $msgs) = $ro_mirror->search->reopen->query('m:m@2');
 		is($nr, 0, "v$v m\@2 gone from Xapian in mirror on $level");
 	}
+
+	# add another message to master and have the mirror
+	# sync and reindex it
+	my @expect = map { $_->{num} } @{$ibx->over->query_ts(0, 0)};
+	foreach my $i (3..5) {
+		$mime->header_set('Message-ID', "<m\@$i>");
+		ok($im->add($mime), "#$i message added");
+		push @expect, $i;
+	}
+	$im->done;
+	is(system('git', "--git-dir=$fetch_dir", qw(fetch -q)), 0, 'fetch OK');
+	is(system($index, '--reindex', $mirror), 0,
+		"v$v index --reindex mirror OK");
+	@ro_nums = map { $_->{num} } @{$ro_mirror->over->query_ts(0, 0)};
+	@rw_nums = map { $_->{num} } @{$ibx->over->query_ts(0, 0)};
+	is_deeply(\@rw_nums, \@expect, "v$v master has expected NNTP articles");
+	is_deeply(\@ro_nums, \@expect, "v$v mirror matches master articles");
 }
 
 # we can probably cull some other tests and put full/medium tests, here
-- 
EW