[PATCH] extindex: support --jobs/-j properly on creation for shard count

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

This wasn't wired up properly, but Xapian appears to suffer from
I/O amplification problems as DB shards get larger:

  https://lists.xapian.org/pipermail/xapian-discuss/2019-February/009727.html
  <23640.32170.703368.841021@y.dockes.com>

Of course, we shouldn't have too many shards, either; because
performance problems with too many shards was the entire reason
extindex was created:

  https://lists.xapian.org/pipermail/xapian-discuss/2020-August/009823.html
  <20200826064728.GA32239@dcvr>
---
 lib/PublicInbox/ExtSearchIdx.pm |  3 ++-
 t/extsearch.t                   | 11 +++++++++++
 2 files changed, 13 insertions(+), 1 deletion(-)

diff --git a/lib/PublicInbox/ExtSearchIdx.pm b/lib/PublicInbox/ExtSearchIdx.pm
index 357312b8..ad56c0d5 100644
--- a/lib/PublicInbox/ExtSearchIdx.pm
+++ b/lib/PublicInbox/ExtSearchIdx.pm
@@ -52,7 +52,8 @@ sub new {
 		parallel => 1,
 		lock_path => "$dir/ei.lock",
 	}, __PACKAGE__;
-	$self->{shards} = $self->count_shards || nproc_shards($opt->{creat});
+	$self->{shards} = $self->count_shards ||
+		nproc_shards({ nproc => $opt->{jobs} });
 	my $oidx = PublicInbox::OverIdx->new("$self->{xpfx}/over.sqlite3");
 	$self->{-no_fsync} = $oidx->{-no_fsync} = 1 if !$opt->{fsync};
 	$self->{oidx} = $oidx;
diff --git a/t/extsearch.t b/t/extsearch.t
index 46a6f2ec..1f62e80c 100644
--- a/t/extsearch.t
+++ b/t/extsearch.t
@@ -411,4 +411,15 @@ if ('dedupe + dry-run') {
 		'--dry-run alone fails');
 }
 
+for my $j (1, 3, 6) {
+	my $o = { 2 => \(my $err = '') };
+	my $d = "$home/extindex-j$j";
+	ok(run_script(['-extindex', "-j$j", '--all', $d], undef, $o),
+		"init with -j$j");
+	my $max = $j - 2;
+	$max = 0 if $max < 0;
+	my @dirs = glob("$d/ei*/?");
+	like($dirs[-1], qr!/ei[0-9]+/$max\z!, '-j works');
+}
+
 done_testing;