+# Copyright (C) 2019 all contributors <meta@public-inbox.org>
+# License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
+use strict;
+use warnings;
+use Test::More;
+my @mods = qw(DBI DBD::SQLite Search::Xapian);
+foreach my $mod (@mods) {
+ eval "require $mod";
+ plan skip_all => "missing $mod for $0" if $@;
+};
+require './t/common.perl';
+require_git('2.6');
+use File::Temp qw/tempdir/;
+use PublicInbox::MIME;
+use PublicInbox::InboxWritable;
+
+my $mime = PublicInbox::MIME->create(
+ header => [
+ From => 'a@example.com',
+ To => 'test@example.com',
+ Subject => 'this is a subject',
+ Date => 'Fri, 02 Oct 1993 00:00:00 +0000',
+ ],
+ body => '',
+);
+
+my ($this) = (split('/', $0))[-1];
+my $tmpdir = tempdir($this.'-XXXXXX', TMPDIR => 1, CLEANUP => 1);
+my $ibx = PublicInbox::Inbox->new({
+ mainrepo => "$tmpdir/testbox",
+ name => $this,
+ version => 2,
+ -primary_address => 'test@example.com',
+ indexlevel => 'medium',
+});
+my $path = 'blib/script';
+my @xcpdb = ("$path/public-inbox-xcpdb", '-q');
+my $nproc = 8;
+my $ndoc = 13;
+my $im = PublicInbox::InboxWritable->new($ibx, {nproc => $nproc})->importer(1);
+for my $i (1..$ndoc) {
+ $mime->header_set('Message-ID', "<m$i\@example.com>");
+ ok($im->add($mime), "message $i added");
+}
+$im->done;
+my @parts = grep(m!/\d+\z!, glob("$ibx->{mainrepo}/xap*/*"));
+is(scalar(@parts), $nproc, 'got expected parts');
+my $orig = $ibx->over->query_xover(1, $ndoc);
+my %nums = map {; "$_->{num}" => 1 } @$orig;
+
+# ensure we can go up or down in partitions, or stay the same:
+for my $R (qw(2 4 1 3 3)) {
+ delete $ibx->{search}; # release old handles
+ is(system(@xcpdb, "-R$R", $ibx->{mainrepo}), 0, "xcpdb -R$R");
+ my @new_parts = grep(m!/\d+\z!, glob("$ibx->{mainrepo}/xap*/*"));
+ is(scalar(@new_parts), $R, 'repartitioned to two parts');
+ my $msgs = $ibx->search->query('s:this');
+ is(scalar(@$msgs), $ndoc, 'got expected docs after repartitioning');
+ my %by_mid = map {; "$_->{mid}" => $_ } @$msgs;
+ ok($by_mid{"m$_\@example.com"}, "$_ exists") for (1..$ndoc);
+
+ delete $ibx->{search}; # release old handles
+
+ # ensure docids in Xapian match NNTP article numbers
+ my $tot = 0;
+ my %tmp = %nums;
+ foreach my $d (@new_parts) {
+ my $xdb = Search::Xapian::Database->new($d);
+ $tot += $xdb->get_doccount;
+ my $it = $xdb->postlist_begin('');
+ my $end = $xdb->postlist_end('');
+ for (; $it != $end; $it++) {
+ my $docid = $it->get_docid;
+ if ($xdb->get_document($docid)) {
+ ok(delete($tmp{$docid}), "saw #$docid");
+ }
+ }
+ }
+ is(scalar keys %tmp, 0, 'all docids seen');
+}
+
+done_testing();
+1;