msgmap: tmp_clone: use in-memory journal

This prevents $TMPDIR from being littered with *-journal files
after running the test suite.

This shouldn't cause excessive memory use since $v2w->{mm_tmp}
doesn't see big transactions.  There's no need to worry about
data loss, here,either, since this is just a temporary clone
we've even disabled fsync on.

Fixes: 78888d36fb80889f ("msgmap: use TRUNCATE for journal_mode, for now")

1 files changed, 1 insertions, 0 deletions

diff --git a/lib/PublicInbox/Msgmap.pm b/lib/PublicInbox/Msgmap.pm
index 5fe14383..a2ffe720 100644
--- a/lib/PublicInbox/Msgmap.pm
+++ b/lib/PublicInbox/Msgmap.pm
@@ -70,6 +70,7 @@ sub tmp_clone {
         $self->{dbh}->sqlite_backup_to_file($fn);
         my $tmp = ref($self)->new_file($fn, 1);
         $tmp->{dbh}->do('PRAGMA synchronous = OFF');
+        $tmp->{dbh}->do('PRAGMA journal_mode = MEMORY');
         $tmp->{tmp_name} = $fn; # SQLite won't work if unlinked, apparently
         $tmp->{pid} = $$;
         close $fh or die "failed to close $fn: $!";