函数的逻辑读成零

drop table t;
CREATE TABLE T AS SELECT * FROM DBA_OBJECTS;

CREATE OR REPLACE FUNCTION F_NO_RESULT_CACHE RETURN NUMBER AS
V_RETURN NUMBER;
BEGIN
SELECT COUNT(*) INTO V_RETURN FROM T;
RETURN V_RETURN;
END;
/

set autotrace on statistics

SELECT F_NO_RESULT_CACHE FROM DUAL;
--看调用F_NO_RESULT_CACHE执行第2次后的结果
SELECT F_NO_RESULT_CACHE FROM DUAL;

CREATE OR REPLACE FUNCTION F_RESULT_CACHE RETURN NUMBER RESULT_CACHE AS
 V_RETURN NUMBER;
 BEGIN
 SELECT COUNT(*) INTO V_RETURN FROM T;
 RETURN V_RETURN;
 END;
/

SELECT F_RESULT_CACHE FROM DUAL;
--看调用F_RESULT_CACHE执行第2次后的结果
SELECT F_RESULT_CACHE FROM DUAL;

函数的逻辑读成零