CCalendarEvent::DeleteEmpty

static function DeleteEmpty()
{
	global $DB;
	if (Util::isSectionStructureConverted())
	{
		$strSql = 'SELECT CE.ID, CE.LOCATION
			FROM b_calendar_event CE
			LEFT JOIN b_calendar_section CS ON (CS.ID=CE.SECTION_ID)
			WHERE CS.ID is null';
	}
	else
	{
		$strSql = 'SELECT CE.ID, CE.LOCATION
			FROM b_calendar_event CE
			LEFT JOIN b_calendar_event_sect CES ON (CE.ID=CES.EVENT_ID)
			WHERE CES.SECT_ID is null';
	}
	$itemIds = [];
	$res = $DB->Query($strSql, false, "FILE: ".__FILE__."
 LINE: ".__LINE__);
	while($arRes = $res->Fetch())
	{
		$loc = $arRes['LOCATION'] ?? null;
		if ($loc && mb_strlen($loc) > 5 && mb_substr($loc, 0, 5) === 'ECMR_')
		{
			$loc = RoomsUtil::parseLocation($loc);
			if ($loc['mrid'] !== false && $loc['mrevid'] !== false) // Release MR
			{
				RoomsUtil::releaseLocation($loc);
			}
		}
		else if ($loc && mb_strlen($loc) > 9 && mb_substr($loc, 0, 9) === 'calendar_')
		{
			$loc = RoomsUtil::parseLocation($loc);
			if ($loc['room_id'] !== false && $loc['room_event_id'] !== false) // Release calendar_room
			{
				RoomsUtil::releaseLocation($loc);
			}
		}
		$itemIds[] = (int)$arRes['ID'];
	}

	// Clean from 'b_calendar_event'
	if (!empty($itemIds))
	{
		$DB->Query("DELETE FROM b_calendar_event WHERE ID in (".implode(',', $itemIds).")", false,
			"FILE: ".__FILE__."
 LINE: ".__LINE__);
	}

	CCalendar::ClearCache(array('section_list', 'event_list'));
}