Very slow query on first chart load

[andk]

Hello,

Zabbix 3.2.6
MariaDB 10.0.32


I have this chart where SWAP usage is shown. The first load of chart is awfully slow.
Using Zabbix debug mode I see the following query taking ages to complete, which is the root cause of slow chart load time. Refreshing same chart works as expected and takes minimum time to complete.

SQL (21.381727): SELECT MIN(h.clock) AS min_clock FROM (SELECT MIN(h.clock) AS clock FROM trends_uint h WHERE h.itemid='213324') h
charts.php:128 → CView->render() → include() → CScreenChart->get() → get_min_itemclock_by_graphid() → get_min_itemclock_by_itemid() → DBselect() in include/graphs.inc.php:241

Running this query directly on SQL server returns instantly. What can bet the source of the problem?

Some other charts hangs on executing :

SQL (23.044088): SELECT MIN(h.clock) AS min_clock FROM (SELECT MIN(h.clock) AS clock FROM trends_uint h WHERE h.itemid='472259' UNION ALL SELECT MIN(h.clock) AS clock FROM trends_uint h WHERE h.itemid='472260' UNION ALL SELECT MIN(h.clock) AS clock FROM trends_uint h WHERE h.itemid='472261' UNION ALL SELECT MIN(h.clock) AS clock FROM trends_uint h WHERE h.itemid='472264') h
charts.php:128 → CView->render() → include() → CScreenChart->get() → get_min_itemclock_by_graphid() → get_min_itemclock_by_itemid() → DBselect() in include/graphs.inc.php:241

[torabkheslat]

HI Guy

What was the result?