imaptracker: preserve WAL journal_mode if set by user

It's no problem for most users to enable WAL, here, since
there's only a single process doing both reading and writing
(unlike the read-only daemons).  However, WAL doesn't work on
network filesystems, so it can't be enabled by default.

1 files changed, 6 insertions, 1 deletions

diff --git a/lib/PublicInbox/IMAPTracker.pm b/lib/PublicInbox/IMAPTracker.pm
index 102a74ce..92f21584 100644
--- a/lib/PublicInbox/IMAPTracker.pm
+++ b/lib/PublicInbox/IMAPTracker.pm
@@ -29,7 +29,12 @@ sub dbh_new ($) {
                 sqlite_use_immediate_transaction => 1,
         });
         $dbh->{sqlite_unicode} = 1;
-        $dbh->do('PRAGMA journal_mode = TRUNCATE');
+
+        # TRUNCATE reduces I/O compared to the default (DELETE).
+        # Allow and preserve user-overridden WAL, but don't force it.
+        my $jm = $dbh->selectrow_array('PRAGMA journal_mode');
+        $dbh->do('PRAGMA journal_mode = TRUNCATE') if $jm ne 'wal';
+
         create_tables($dbh);
         $dbh;
 }