Fix database prune, offset not working on some dbs (#948)

* Use left join to optimize prune query, and avoid using offset

Author: erikn69

src/Drivers/Database.php

@@ -23,9 +23,22 @@ public function audit(Auditable $model): ?Audit
     public function prune(Auditable $model): bool
     {
         if (($threshold = $model->getAuditThreshold()) > 0) {
+            $auditClass = get_class($model->audits()->getModel());
+            $auditModel = new $auditClass;
+
             return $model->audits()
-                ->latest()
-                ->offset($threshold)->limit(PHP_INT_MAX)
+                ->leftJoinSub(
+                    $model->audits()->select($auditModel->getKeyName())->limit($threshold)->latest(),
+                    'audit_threshold',
+                    function ($join) use ($auditModel) {
+                        $join->on(
+                            $auditModel->gettable().'.'.$auditModel->getKeyName(),
+                            '=',
+                            'audit_threshold.'.$auditModel->getKeyName()
+                        );
+                    }
+                )
+                ->whereNull('audit_threshold.'.$auditModel->getKeyName())
                 ->delete() > 0;
         }
 

tests/Functional/AuditingTest.php

@@ -297,16 +297,23 @@ public function itWillRemoveOlderAuditsAboveTheThreshold()
         ]);
 
         $article = factory(Article::class)->create([
-            'reviewed' => 1,
+            'title' => 'Title #0',
         ]);
 
-        foreach (range(0, 99) as $count) {
+        foreach (range(1, 20) as $count) {
+            if ($count === 11) {
+                sleep(1);
+            }
+
             $article->update([
-                'reviewed' => ($count % 2),
+                'title' => 'Title #' . $count,
             ]);
         }
 
-        $this->assertSame(10, $article->audits()->count());
+        $audits = $article->audits()->get();
+        $this->assertSame(10, $audits->count());
+        $this->assertSame('Title #11', $audits->first()->new_values['title']);
+        $this->assertSame('Title #20', $audits->last()->new_values['title']);
     }
 
     /**