postgresql - 从表中返回单行的函数

Question

我这辈子都不能让这个函数正确地返回一行(它只会在我查询主键时返回一行)。看起来像这样。

CREATE OR REPLACE FUNCTION sch.getrow(
    IN gy integer,
    IN gw integer,
    IN pi uuid)
RETURNS SETOF record AS $$

BEGIN

EXECUTE 'SELECT * FROM sch.foo WHERE gy = $1 AND gw = $2 AND idpi = $3' INTO record USING gy, gw, pi;

END

$$
LANGUAGE plpgsql IMMUTABLE;

尝试各种RETURN EXECUTE 和RETURN QUERY 等，但是 nada:SQL 字符串将是一个动态定义的字符串，因为表名最终会根据输入而改变变量。

Answer 1

如果函数返回 SETOF，您可以使用 RETURN QUERY，无论函数可以返回多少行(一行或多行)。

CREATE OR REPLACE FUNCTION sch.getrow(
    IN gy integer,
    IN gw integer,
    IN pi uuid)
RETURNS SETOF record AS $$
BEGIN
    RETURN QUERY
    EXECUTE 'SELECT * FROM sch.foo WHERE gy = $1 AND gw = $2 AND idpi = $3' USING gy, gw, pi;

END

$$
LANGUAGE plpgsql;

不相关但很重要。该函数不应定义为 IMMUTABLE，因为它的结果取决于表中存储的数据。每the documentation:

IMMUTABLE indicates that the function cannot modify the database and always returns the same result when given the same argument values; that is, it does not do database lookups or otherwise use information not directly present in its argument list.