pbackup: Use SQL to find jobs for FULL

FULL backups want only jobs without existing stat records. Usually,
there will be none. Select jobs without stat records by `LEFT JOIN
stat ON stat_job_id = job_id WHERE stat_job_id IS NULL`.

This reduced the time for test runs to discover that there are no FULL
jobs to do in an actual database from 2.02 seconds to 0.06 seconds.

bin/pbackup

@@ -520,15 +520,30 @@ sub do_a_job {
 
     $dbh->begin_work();
 
-    my $sth = $dbh->prepare('
-SELECT job_id,job_name,job_ok,job_started,path_server,path_path,
-CASE WHEN job_ok THEN job_started-? ELSE JOB_STARTED-? END as due
-FROM job,path
-WHERE job_path_id=path_id
+    my $sth;
+    if ($type eq 'F') {
+        $sth = $dbh->prepare('
+SELECT job_id, job_name, job_ok, job_started, path_server, path_path,
+CASE WHEN job_ok THEN job_started - ? ELSE JOB_STARTED - ? END as due
+FROM job
+LEFT JOIN stat ON stat_job_id = job_id
+INNER JOIN path ON path_id = job_path_id
+WHERE stat_job_id IS NULL
 AND job_enabled
-AND due<=0
+AND due <= 0
 ORDER BY due
 ');
+    } else {
+        $sth = $dbh->prepare('
+SELECT job_id, job_name, job_ok, job_started, path_server, path_path,
+CASE WHEN job_ok THEN job_started - ? ELSE JOB_STARTED - ? END as due
+FROM job
+INNER JOIN path ON job_path_id = path_id
+WHERE job_enabled
+AND due <= 0
+ORDER BY due
+');
+    }
     $sth->execute(time-24*60*60, time-8*60*60);
     my ($job_id, $job_name, $job_ok, $job_started, $path_server, $path_path, $due);
     my $datadir;