SQL (0.000519): 
SELECT MIN(ht.c) AS min_clock FROM (
SELECT MIN(ht.clock) AS c FROM trends ht WHERE ht.itemid='23299' UNION ALL 
SELECT MIN(ht.clock) AS c FROM trends ht WHERE ht.itemid='23300' UNION ALL 
SELECT MIN(ht.clock) AS c FROM trends ht WHERE ht.itemid='23301'
) ht
charts.php:162 → CView->render() → include() → CScreenChart->get() → get_min_itemclock_by_graphid() → get_min_itemclock_by_itemid() → DBselect() in /zab/www-dev/2.4/include/graphs.inc.php:269


SQL (0.000576): 
SELECT MIN(ht.c) AS min_clock FROM (
SELECT MIN(ht.clock) AS c FROM trends ht WHERE ht.itemid='23299' UNION ALL 
SELECT MIN(ht.clock) AS c FROM trends ht WHERE ht.itemid='23300' UNION ALL 
SELECT MIN(ht.clock) AS c FROM trends ht WHERE ht.itemid='23301' UNION ALL 
SELECT MIN(ht.clock) AS c FROM trends_uint ht WHERE ht.itemid='23299' UNION ALL 
SELECT MIN(ht.clock) AS c FROM trends_uint ht WHERE ht.itemid='23300' UNION ALL 
SELECT MIN(ht.clock) AS c FROM trends_uint ht WHERE ht.itemid='23301') ht
charts.php:162 → CView->render() → include() → CScreenChart->get() → get_min_itemclock_by_graphid() → get_min_itemclock_by_itemid() → DBselect() in /zab/www-dev/2.4/include/graphs.inc.php:269

SQL (0.000527): 
SELECT MIN(ht.c) AS min_clock FROM (
SELECT MIN(ht.clock) AS c FROM trends ht WHERE ht.itemid IN ('23300','23301') UNION ALL 
SELECT MIN(ht.clock) AS c FROM trends_uint ht WHERE ht.itemid='23299'
) ht
charts.php:162 → CView->render() → include() → CScreenChart->get() → get_min_itemclock_by_graphid() → get_min_itemclock_by_itemid() → DBselect() in /zab/www-dev/2.4/include/graphs.inc.php:267

Index: include/graphs.inc.php
===================================================================
--- include/graphs.inc.php      (revision 56332)
+++ include/graphs.inc.php      (working copy)
@@ -258,19 +258,14 @@
                        default:
                                $sqlFrom = 'history';
                }
-
-               foreach ($itemIds as $itemId) {
-                       $sqlUnions[] = 'SELECT MIN(ht.clock) AS c FROM '.$sqlFrom.' ht WHERE ht.itemid='.zbx_dbstr($itemId);
-               }
-
-               $dbMin = DBfetch(DBselect(
-                       'SELECT MIN(ht.c) AS min_clock'.
-                       ' FROM ('.implode(' UNION ALL ', $sqlUnions).') ht'
+
+               $sqlUnions[] = 'SELECT MIN(ht.clock) AS c FROM '.$sqlFrom.' ht WHERE '.dbConditionInt('ht.itemid', $items);
+       }
+       $dbMin = DBfetch(DBselect(
+               'SELECT MIN(ht.c) AS min_clock'.
+               ' FROM ('.implode(' UNION ALL ', $sqlUnions).') ht'
                ));
-
-               $min = $min ? min($min, $dbMin['min_clock']) : $dbMin['min_clock'];
-       }
-
+       $min = $dbMin['min_clock'];
        // in case DB clock column is corrupted having negative numbers, return min clock from max possible history storage
        return ($min > 0) ? $min : $result;
 }