[PATCH 06/13] msgmap: add tmp_clone to create an anonymous copy

["Eric Wong (Contractor, The Linux Foundation)" <e@80x24.org>]

This will be used to keep track of Message-ID <-> NNTP Article
numbers to prevent article number reuse when reindexing.
---
 lib/PublicInbox/Inbox.pm  |  2 +-
 lib/PublicInbox/Msgmap.pm | 19 +++++++++++++++++++
 t/msgmap.t                |  4 ++++
 3 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/lib/PublicInbox/Inbox.pm b/lib/PublicInbox/Inbox.pm
index b9cd4c4..f307038 100644
--- a/lib/PublicInbox/Inbox.pm
+++ b/lib/PublicInbox/Inbox.pm
@@ -75,7 +75,7 @@ sub new {
 	_set_uint($opts, 'feedmax', 25);
 	$opts->{nntpserver} ||= $pi_config->{'publicinbox.nntpserver'};
 	my $dir = $opts->{mainrepo};
-	if (defined $dir && -f "$dir/msgmap.sqlite3") { # XXX DIRTY
+	if (defined $dir && -f "$dir/inbox.lock") {
 		$opts->{version} = 2;
 	}
 	bless $opts, $class;
diff --git a/lib/PublicInbox/Msgmap.pm b/lib/PublicInbox/Msgmap.pm
index 8e81fba..78922d3 100644
--- a/lib/PublicInbox/Msgmap.pm
+++ b/lib/PublicInbox/Msgmap.pm
@@ -12,6 +12,7 @@ use strict;
 use warnings;
 use DBI;
 use DBD::SQLite;
+use File::Temp qw(tempfile);
 
 sub new {
 	my ($class, $git_dir, $writable) = @_;
@@ -45,6 +46,18 @@ sub new_file {
 	$self;
 }
 
+# used to keep track of used numeric mappings for v2 reindex
+sub tmp_clone {
+	my ($self) = @_;
+	my ($fh, $fn) = tempfile(EXLOCK => 0);
+	$self->{dbh}->sqlite_backup_to_file($fn);
+	my $tmp = ref($self)->new_file($fn, 1);
+	$tmp->{dbh}->do('PRAGMA synchronous = OFF');
+	$tmp->{tmp_name} = $fn; # SQLite won't work if unlinked, apparently
+	$fh = undef;
+	$tmp;
+}
+
 # n.b. invoked directly by scripts/xhdr-num2mid
 sub meta_accessor {
 	my ($self, $key, $value) = @_;
@@ -189,4 +202,10 @@ sub mid_set {
 	$sth->execute($num, $mid);
 }
 
+sub DESTROY {
+	my ($self) = @_;
+	delete $self->{dbh};
+	unlink $self->{tmp_name} if defined $self->{tmp_name};
+}
+
 1;
diff --git a/t/msgmap.t b/t/msgmap.t
index bc22137..dce98f4 100644
--- a/t/msgmap.t
+++ b/t/msgmap.t
@@ -65,4 +65,8 @@ my $orig = $d->mid_insert('spam@1');
 $d->mid_delete('spam@1');
 is($d->mid_insert('spam@2'), 1 + $orig, "last number not recycled");
 
+my $tmp = $d->tmp_clone;
+is_deeply([$d->minmax], [$tmp->minmax], 'Cloned temporary DB matches');
+ok($tmp->mid_delete('spam@2'), 'temporary DB is writable');
+
 done_testing();
-- 
EW