游标检索在 plpgsql 函数中创建的 table 中已删除的行

Question

在 plpgsql 函数中，我创建了一个 table 并使用游标访问它的行。在第一行，我删除了下一行，令人惊讶的是（至少对我而言）游标获取了它。在同一个函数中重复时，它按我预期的那样工作。

但是，如果 table 预先存在并且不是在函数内创建的，则永远不会提取已删除的行。

我错过了什么？

DECLARE
curs1 refcursor;
rec record;

BEGIN
CREATE TABLE test as select generate_series(1,5,1) test_id;

OPEN curs1 FOR SELECT * FROM test ORDER BY test_id; 
  LOOP
    FETCH curs1 INTO rec;
    EXIT WHEN NOT FOUND;
    RAISE NOTICE 'ROW:%',rec.test_id;
    IF rec.test_id=1 THEN
      DELETE FROM TEST WHERE test_id=3;
    END IF;
  END LOOP;
CLOSE curs1;

RAISE NOTICE 'AGAIN';
--just repeating without deleting

OPEN curs1 FOR SELECT * FROM test ORDER BY test_id; 
  LOOP
    FETCH curs1 INTO rec;
    EXIT WHEN NOT FOUND;
    RAISE NOTICE 'ROW:%',rec.test_id;
  END LOOP;
CLOSE curs1;

输出为：

NOTICE:  ROW:1
NOTICE:  ROW:2
NOTICE:  ROW:3
NOTICE:  ROW:4
NOTICE:  ROW:5
NOTICE:  AGAIN
NOTICE:  ROW:1
NOTICE:  ROW:2
NOTICE:  ROW:4
NOTICE:  ROW:5

Answer 1

原因是 Postgres 游标默认为 "insensitive"。 The documentation:

The SQL standard says that it is implementation-dependent whether cursors are sensitive to concurrent updates of the underlying data by default. In PostgreSQL, cursors are insensitive by default, and can be made sensitive by specifying FOR UPDATE. Other products may work differently.

大胆强调我的。

所以尝试使用 FOR UPDATE 子句：

DO
$$
DECLARE
   curs1 refcursor;
   rec record;
BEGIN
   CREATE TABLE test AS SELECT generate_series(1,5) test_id;

   OPEN curs1 FOR SELECT * FROM test ORDER BY test_id <b>FOR UPDATE</b>; 
   DELETE FROM test WHERE test_id = 3;
   LOOP
      FETCH curs1 INTO rec;
      EXIT WHEN NOT FOUND;
      RAISE NOTICE 'ROW:%',rec.test_id;
   END LOOP;
   CLOSE curs1;
END
$$

你得到：

NOTICE:  ROW:1
NOTICE:  ROW:2
NOTICE:  ROW:4
NOTICE:  ROW:5

第 3 行不再可见。

游标检索在 plpgsql 函数中创建的 table 中已删除的行

Cursor retrieves a deleted row in table created within plpgsql function

postgresql

plpgsql

cursor