nntp: support slow blob retrievals

[public-inbox.git] / lib / PublicInbox / Msgmap.pm

diff --git a/lib/PublicInbox/Msgmap.pm b/lib/PublicInbox/Msgmap.pm
index 8aaa06b268f7e1d90ce6c2f583752b7677c846ab..d115cbce352cd3551b406d5b5c9d90782e9feab1 100644 (file)
--- a/lib/PublicInbox/Msgmap.pm
+++ b/lib/PublicInbox/Msgmap.pm
@@ -1,4 +1,4 @@
-# Copyright (C) 2015-2019 all contributors <meta@public-inbox.org>
+# Copyright (C) 2015-2020 all contributors <meta@public-inbox.org>
 # License: AGPL-3.0+ <https://www.gnu.org/licenses/agpl-3.0.txt>
 
 # bidirectional Message-ID <-> Article Number mapping for the NNTP
@@ -48,11 +48,14 @@ sub new_file {
 
        if ($writable) {
                create_tables($dbh);
+
+               # TRUNCATE reduces I/O compared to the default (DELETE)
+               $dbh->do('PRAGMA journal_mode = TRUNCATE');
+
                $dbh->begin_work;
                $self->created_at(time) unless $self->created_at;
 
-               my (undef, $max) = $self->minmax();
-               $max ||= 0;
+               my $max = $self->max // 0;
                $self->num_highwater($max);
                $dbh->commit;
        }
@@ -66,6 +69,7 @@ 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: $!";
@@ -154,17 +158,20 @@ sub num_for {
        $sth->fetchrow_array;
 }
 
+sub max {
+       my $sth = $_[0]->{dbh}->prepare_cached('SELECT MAX(num) FROM msgmap',
+                                               undef, 1);
+       $sth->execute;
+       $sth->fetchrow_array;
+}
+
 sub minmax {
-       my ($self) = @_;
-       my $dbh = $self->{dbh};
        # breaking MIN and MAX into separate queries speeds up from 250ms
        # to around 700us with 2.7million messages.
-       my $sth = $dbh->prepare_cached('SELECT MIN(num) FROM msgmap', undef, 1);
-       $sth->execute;
-       my $min = $sth->fetchrow_array;
-       $sth = $dbh->prepare_cached('SELECT MAX(num) FROM msgmap', undef, 1);
+       my $sth = $_[0]->{dbh}->prepare_cached('SELECT MIN(num) FROM msgmap',
+                                               undef, 1);
        $sth->execute;
-       ($min, $sth->fetchrow_array);
+       ($sth->fetchrow_array, max($_[0]));
 }
 
 sub mid_delete {