index: --sequential-shard works incrementally

We should never reindex all data in Xapian unless --reindex is
specified on the command-line.  This means users who put
publicInbox.indexSequentialShard in their config file won't have
to put up with a full reindex at every invocation, only when
they specify --reindex.

We'll also cleanup the progress output to not emit non-sensical
ranges where the starting number is higher than the end.

1 files changed, 23 insertions, 13 deletions

diff --git a/lib/PublicInbox/V2Writable.pm b/lib/PublicInbox/V2Writable.pm
index dfcb4897..8148439a 100644
--- a/lib/PublicInbox/V2Writable.pm
+++ b/lib/PublicInbox/V2Writable.pm
@@ -1197,20 +1197,20 @@ sub index_xap_only { # git->cat_async callback
 
 sub index_xap_step ($$$;$) {
         my ($self, $sync, $beg, $step) = @_;
-        my $ibx = $self->{ibx};
-        my $all = $ibx->git;
-        my $over = $ibx->over;
-        my $batch_bytes = batch_bytes($self);
-        $step //= $self->{shards};
         my $end = $sync->{art_end};
+        return if $beg > $end; # nothing to do
+
+        $step //= $self->{shards};
+        my $ibx = $self->{ibx};
         if (my $pr = $sync->{-opt}->{-progress}) {
                 $pr->("Xapian indexlevel=$ibx->{indexlevel} ".
                         "$beg..$end (% $step)\n");
         }
+        my $batch_bytes = batch_bytes($self);
         for (my $num = $beg; $num <= $end; $num += $step) {
-                my $smsg = $over->get_art($num) or next;
+                my $smsg = $ibx->over->get_art($num) or next;
                 $smsg->{v2w} = $self;
-                $all->cat_async($smsg->{blob}, \&index_xap_only, $smsg);
+                $ibx->git->cat_async($smsg->{blob}, \&index_xap_only, $smsg);
                 if ($self->{transact_bytes} >= $batch_bytes) {
                         ${$sync->{nr}} = $num;
                         reindex_checkpoint($self, $sync);
@@ -1252,8 +1252,9 @@ sub index_epoch ($$$) {
 }
 
 sub xapian_only {
-        my ($self, $opt, $sync) = @_;
+        my ($self, $opt, $sync, $art_beg) = @_;
         my $seq = $opt->{sequentialshard};
+        $art_beg //= 0;
         local $self->{parallel} = 0 if $seq;
         $self->idx_init($opt); # acquire lock
         if (my $art_end = $self->{ibx}->mm->max) {
@@ -1267,9 +1268,11 @@ sub xapian_only {
                 $sync->{art_end} = $art_end;
                 if ($seq || !$self->{parallel}) {
                         my $shard_end = $self->{shards} - 1;
-                        index_xap_step($self, $sync, $_) for (0..$shard_end);
+                        for (0..$shard_end) {
+                                index_xap_step($self, $sync, $art_beg + $_)
+                        }
                 } else { # parallel (maybe)
-                        index_xap_step($self, $sync, 0, 1);
+                        index_xap_step($self, $sync, $art_beg, 1);
                 }
         }
         $self->{ibx}->git->cat_async_wait;
@@ -1288,6 +1291,7 @@ sub index_sync {
         return unless defined $latest;
 
         my $seq = $opt->{sequentialshard};
+        my $art_beg; # the NNTP article number we start xapian_only at
         my $idxlevel = $self->{ibx}->{indexlevel};
         local $self->{ibx}->{indexlevel} = 'basic' if $seq;
 
@@ -1311,6 +1315,12 @@ sub index_sync {
                 $self->{mm}->{dbh}->begin_work;
                 $sync->{mm_tmp} =
                         $self->{mm}->tmp_clone($self->{ibx}->{inboxdir});
+
+                # xapian_only works incrementally w/o --reindex
+                if ($seq && !$opt->{reindex}) {
+                        $art_beg = $sync->{mm_tmp}->max;
+                        $art_beg++ if defined($art_beg);
+                }
         }
         if ($sync->{index_max_size} = $self->{ibx}->{index_max_size}) {
                 $sync->{index_oid} = \&index_oid;
@@ -1325,10 +1335,10 @@ sub index_sync {
                 $pr->('all.git '.sprintf($sync->{-regen_fmt}, $$nr)) if $pr;
         }
 
-        if ($seq) { # deal with Xapian shards sequentially
+        # deal with Xapian shards sequentially
+        if ($seq && delete($sync->{mm_tmp})) {
                 $self->{ibx}->{indexlevel} = $idxlevel;
-                delete $sync->{mm_tmp};
-                xapian_only($self, $opt, $sync);
+                xapian_only($self, $opt, $sync, $art_beg);
         }
 
         # reindex does not pick up new changes, so we rerun w/o it: