v2writable: support reindexing Xapian

This still requires a msgmap.sqlite3 file to exist, but
it allows us to tweak Xapian indexing rules and reindex
the Xapian database online while -watch is running.

1 files changed, 34 insertions, 6 deletions

diff --git a/lib/PublicInbox/Msgmap.pm b/lib/PublicInbox/Msgmap.pm
index 78922d36..12833050 100644
--- a/lib/PublicInbox/Msgmap.pm
+++ b/lib/PublicInbox/Msgmap.pm
@@ -24,9 +24,8 @@ sub new {
         new_file($class, "$d/msgmap.sqlite3", $writable);
 }
 
-sub new_file {
-        my ($class, $f, $writable) = @_;
-
+sub dbh_new {
+        my ($f, $writable) = @_;
         my $dbh = DBI->connect("dbi:SQLite:dbname=$f",'','', {
                 AutoCommit => 1,
                 RaiseError => 1,
@@ -35,6 +34,13 @@ sub new_file {
                 sqlite_use_immediate_transaction => 1,
         });
         $dbh->do('PRAGMA case_sensitive_like = ON');
+        $dbh;
+}
+
+sub new_file {
+        my ($class, $f, $writable) = @_;
+
+        my $dbh = dbh_new($f, $writable);
         my $self = bless { dbh => $dbh }, $class;
 
         if ($writable) {
@@ -49,12 +55,13 @@ sub new_file {
 # used to keep track of used numeric mappings for v2 reindex
 sub tmp_clone {
         my ($self) = @_;
-        my ($fh, $fn) = tempfile(EXLOCK => 0);
+        my ($fh, $fn) = tempfile('msgmap-XXXXXXXX', EXLOCK => 0, TMPDIR => 1);
         $self->{dbh}->sqlite_backup_to_file($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->{pid} = $$;
+        close $fh or die "failed to close $fn: $!";
         $tmp;
 }
 
@@ -205,7 +212,28 @@ sub mid_set {
 sub DESTROY {
         my ($self) = @_;
         delete $self->{dbh};
-        unlink $self->{tmp_name} if defined $self->{tmp_name};
+        my $f = delete $self->{tmp_name};
+        if (defined $f && $self->{pid} == $$) {
+                unlink $f or warn "failed to unlink $f: $!\n";
+        }
+}
+
+sub atfork_parent {
+        my ($self) = @_;
+        my $f = $self->{tmp_name} or die "not a temporary clone\n";
+        delete $self->{dbh} and die "tmp_clone dbh not prepared for parent";
+        my $dbh = $self->{dbh} = dbh_new($f, 1);
+        $dbh->do('PRAGMA synchronous = OFF');
+}
+
+sub atfork_prepare {
+        my ($self) = @_;
+        my $f = $self->{tmp_name} or die "not a temporary clone\n";
+        $self->{pid} == $$ or
+                die "BUG: atfork_prepare not called from $self->{pid}\n";
+        $self->{dbh} or die "temporary clone not open\n";
+        # must clobber prepared statements
+        %$self = (tmp_name => $f, pid => $$);
 }
 
 1;