[media] Caching instrument names (#8055)

This adds a test name cache in the getInstance function of the media provisioner to load each instrument only once instead of for each row.

Resolves #8033

modules/media/php/mediafileprovisioner.class.inc

@@ -32,6 +32,15 @@ class MediaFileProvisioner extends \LORIS\Data\Provisioners\DBRowProvisioner
 {
     protected $lorisinstance;
 
+    /**
+     * Cache of instrument->getFullname returned value.
+     * Initializing empty keys to prevent instanciation of empty testnames.
+     */
+    private $_instrumentnames = [
+        null => '',
+        ''   => ''
+    ];
+
     /**
      * Create a MediaFileProvisioner, which gets files for the meida
      * menu table.
@@ -80,18 +89,17 @@ class MediaFileProvisioner extends \LORIS\Data\Provisioners\DBRowProvisioner
      */
     public function getInstance($row) : \LORIS\Data\DataInstance
     {
-        if (!is_null($row['testName'])) {
-            try {
-                $instrumentName  = \NDB_BVL_Instrument::factory(
-                    $this->lorisinstance,
-                    $row['testName'],
-                )->getFullname();
-                $row['fullName'] = $instrumentName;
-            } catch (\Exception $e) {
-            }
-        }
+        $testname = $row['testName'] ?? '';
         unset($row['testName']);
 
+        if (!isset($this->_instrumentnames[$testname])) {
+            $this->_instrumentnames[$testname] = \NDB_BVL_Instrument::factory(
+                $this->lorisinstance,
+                $testname,
+            )->getFullname();
+        }
+        $row['fullName'] = $this->_instrumentnames[$testname] ?? null;
+
         return new MediaFile($row);
     }
 }