一致的标量函数结果

过程（或匿名块）中使用的隐式 SELECT 语句在过程完成后执行，标量用户定义的函数 (SUDF) 在 SELECT 语句的读取时进行评估，因为设计了后期实现。为避免出现超出过程或 SUDF 中语句快照顺序的语句的意外结果，现在将实例化隐式结果集，以防 SUDF 引用持久表。

CREATE TABLE t1(C1 VARCHAR(20));
CREATE FUNCTION my_count RETURNS v_result INTEGER AS
BEGIN
    SELECT COUNT(*) INTO v_result FROM t1;
END;
CREATE PROCEDURE proc_insert_delete AS
BEGIN
    INSERT INTO t1 VALUES ('test');
    SELECT 'TRACE 1: COUNT AFTER INSERT', COUNT(*) FROM t1;
    SELECT 'TRACE 2: COUNT DURING FUNCTION CALL', my_count() FROM DUMMY;
    DELETE FROM t1;
    SELECT 'TRACE 3: COUNT AFTER DELETE', COUNT(*) FROM t1;
    COMMIT;
END;
CALL proc_insert_delete;
-- ('TRACE 1: COUNT AFTER INSERT', 1),
-- ('TRACE 2: COUNT DURING FUNCTION CALL', 1),
-- ('TRACE 3: COUNT AFTER DELETE', 0),