[PATCH 6/8] extindex: --gc doesn't touch ghost entries

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

We were deleting ghost entries, this was usually harmless since
other messages could fill-in-the-blanks, but could cause
misthreading in odd cases where a big chunk of a thread is
missing and the latest messages only referenced ghosts.

We'll also save some cycles when scanning Xapian shards since
docids won't be <= 0.
---
 lib/PublicInbox/ExtSearchIdx.pm | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/lib/PublicInbox/ExtSearchIdx.pm b/lib/PublicInbox/ExtSearchIdx.pm
index 42488e12..acf35e3d 100644
--- a/lib/PublicInbox/ExtSearchIdx.pm
+++ b/lib/PublicInbox/ExtSearchIdx.pm
@@ -425,13 +425,13 @@ DELETE FROM xref3 WHERE docid NOT IN (SELECT num FROM over)
 
 	# fixup from old bugs:
 	$nr = $self->{oidx}->dbh->do(<<'');
-DELETE FROM over WHERE num NOT IN (SELECT docid FROM xref3)
+DELETE FROM over WHERE num > 0 AND num NOT IN (SELECT docid FROM xref3)
 
 	warn "I: eliminated $nr stale over entries\n" if $nr != 0;
 	reindex_checkpoint($self, $sync) if checkpoint_due($sync);
 
 	my ($cur) = $self->{oidx}->dbh->selectrow_array(<<EOM);
-SELECT MIN(num) FROM over
+SELECT MIN(num) FROM over WHERE num > 0
 EOM
 	$cur // return; # empty
 	my ($r, $n, %active);