public function itemsFilterHash($params){
		$db=\Brilliant\BFactory::getDBO();
		$itemshash=parent::itemsFilterHash($params);

		//Select categories only with some level
		if(isset($params['level'])){
			$itemshash.=':level='.$params['level'];
			}
		//Select categories only with parentid=$params['parent'].
		if(isset($params['parent'])){
			$itemshash.=':parent='.$params['parent'];
			}
		//Entire parents tree. 
		if(isset($params['parenttree'])){
			$itemid=(int)$params['parenttree'];
			$item=$this->itemGet($itemid);
			if(empty($item)){
				return false;
				}
			$itemshash.=':parenttree-'.$item->lft.'-'.$item->rgt;
			}
		//Entire parents tree, second version. 
		if((isset($params['parenttree_lft']))&&(isset($params['parenttree_rgt']))){
			$lft=$params['parenttree_lft'];
			$rgt=$params['parenttree_rgt'];
			if(($lft<1)||($rgt<1)||($lft>=$rgt)){
				return false;
				}
			$itemshash.=':parenttree-'.$lft.'-'.$rgt;
			}
		//Entire parents chain. 
		if(isset($params['parentchain'])){
			$itemid=(int)$params['parentchain'];
			$item=$this->itemGet($itemid);
			if(empty($item)){
				return false;
				}
			$itemshash.=':parentchain-'.$item->lft.'-'.$item->rgt;
			}
		//Entire parents chain, second version. 
		if((isset($params['parentchain_lft']))&&(isset($params['parentchain_rgt']))){
			$lft=$params['parentchain_lft'];
			$rgt=$params['parentchain_rgt'];
			if(($lft<1)||($rgt<1)||($lft>=$rgt)){
				return false;
				}
			$itemshash.=':parentchain-'.$lft.'-'.$rgt;
			}
		return $itemshash;
		}