vaultLoop: use MAX(running_balance) per user instead of SUM(amount)

includes/utilities.php

@@ -200,14 +200,22 @@ function fetchVaultRecords($user = null) {
  * @return int The total balance of the given user (or all users if no user is given).
  */
 function vaultLoop ($name=null) {
-    $vault   = fetchVaultRecords($name);
-    $balance = 0;
+    $pdo = getDatabaseConnection();
 
-    foreach ($vault as $entry) {
-        $balance += $entry['amount'];
+    if ($name === null) {
+        $stmt = $pdo->query(
+            'SELECT COALESCE(SUM(max_balance), 0) FROM '
+            . '(SELECT MAX(running_balance) AS max_balance FROM vault GROUP BY user)'
+        );
+
+        return (int)$stmt->fetchColumn();
     }
 
-    return $balance;
+    $stmt = $pdo->prepare('SELECT MAX(running_balance) FROM vault WHERE user = :user');
+    $stmt->bindValue(':user', $name);
+    $stmt->execute();
+
+    return (int)$stmt->fetchColumn();
 }
 
 /**