MariaDB 10.2.6 eats virtual memory

SELECT 

      tbl_tmp_import_deals_etl1.counterparty_id,

      tbl_tmp_import_deals_etl1.deal_id_kits AS `deal_id`,

      GET_SUB_PORTFOLIO_DEAL_GERMANY(tbl_tmp_import_deals_etl1.deal_id_scpm) AS `sub_portfolio`

  FROM

      tbl_tmp_import_deals_etl1;

DROP FUNCTION IF EXISTS test_database.GET_SUB_PORTFOLIO_DEAL_GERMANY;

CREATE FUNCTION test_database.`GET_SUB_PORTFOLIO_DEAL_GERMANY`(v_deal_id BIGINT(20)) RETURNS varchar(50) CHARSET utf8 COLLATE utf8_unicode_ci

    READS SQL DATA

    DETERMINISTIC

BEGIN

DECLARE r_rueck VARCHAR(50);

SELECT IFNULL(value,'no subportfolio') FROM tbl_tmp_import_deal_type_detail

       WHERE deal_id_scpm = v_deal_id AND upper(description) = 'GESELLSCHAFT'

  INTO r_rueck;	

	RETURN r_rueck;

END;