A lot less queries thanks to efficient query.

app/Generator/Chart/Account/ChartJsAccountChartGenerator.php

@@ -3,10 +3,8 @@
 namespace FireflyIII\Generator\Chart\Account;
 
 use Carbon\Carbon;
-use Config;
 use FireflyIII\Models\Account;
 use Illuminate\Support\Collection;
-use Preferences;
 use Steam;
 
 /**
@@ -102,6 +100,7 @@ class ChartJsAccountChartGenerator implements AccountChartGenerator
             $current->addDay();
         }
 
+
         foreach ($accounts as $account) {
             $set      = [
                 'label'                => $account->name,
@@ -114,8 +113,14 @@ class ChartJsAccountChartGenerator implements AccountChartGenerator
                 'data'                 => [],
             ];
             $current  = clone $start;
+            $range    = Steam::balanceInRange($account, $start, $end);
+            $previous = array_values($range)[0];
             while ($current <= $end) {
-                $set['data'][] = Steam::balance($account, $current);
+                $format  = $current->format('Y-m-d');
+                $balance = isset($range[$format]) ? $range[$format] : $previous;
+
+                $set['data'][] = $balance;
+                $previous      = $balance;
                 $current->addDay();
             }
             $data['datasets'][] = $set;

app/Support/Steam.php

@@ -72,6 +72,54 @@ class Steam
         return round($balance, 2);
     }
 
+    /**
+     * Gets the balance for the given account during the whole range, using this format:
+     *
+     * [yyyy-mm-dd] => 123,2
+     *
+     * @param Account $account
+     * @param Carbon  $start
+     * @param Carbon  $end
+     */
+    public function balanceInRange(Account $account, Carbon $start, Carbon $end)
+    {
+        // abuse chart properties:
+        $cache = new CacheProperties;
+        $cache->addProperty($account->id);
+        $cache->addProperty('balance-in-range');
+        $cache->addProperty($start);
+        $cache->addProperty($end);
+        if ($cache->has()) {
+            return $cache->get(); // @codeCoverageIgnore
+        }
+
+        $balances = [];
+        $start->subDay();
+        $end->addDay();
+        $startBalance                      = $this->balance($account, $start);
+        $balances[$start->format('Y-m-d')] = $startBalance;
+        $start->addDay();
+
+        // query!
+        $set            = $account->transactions()
+                                  ->leftJoin('transaction_journals', 'transactions.transaction_journal_id', '=', 'transaction_journals.id')
+                                  ->where('transaction_journals.date', '>=', $start->format('Y-m-d'))
+                                  ->where('transaction_journals.date', '<=', $end->format('Y-m-d'))
+                                  ->groupBy('transaction_journals.date')
+                                  ->get(['transaction_journals.date', DB::Raw('SUM(`transactions`.`amount`) as `modified`')]);
+        $currentBalance = $startBalance;
+        foreach ($set as $entry) {
+            $currentBalance         = bcadd($currentBalance, $entry->modified);
+            $balances[$entry->date] = $currentBalance;
+        }
+
+        $cache->store($balances);
+
+        return $balances;
+
+
+    }
+
     /**
      *
      * @param array          $ids