PG function with pseudotype "anyelement" for IN, OUT parameter shows wrong behaviour.

pá 29. 5. 2020 v 16:45 odesílatel Prabhat Sahu <
prabhat.sahu@enterprisedb.com> napsal:

Hi All,

Please check the below scenario, with pseudotype "anyelement" for IN, OUT
parameter and the RETURN record in a function.

postgres=# create table tab1(c1 int, c2 int, c3 timestamp) ;
CREATE TABLE
postgres=# CREATE OR REPLACE FUNCTION func_any(IN anyelement, IN
anyelement, OUT v1 anyelement, OUT v2 anyelement)
RETURNS record
AS
$$
BEGIN
SELECT $1 + 1, $2 + 1 into v1, v2;
insert into tab1 values(v1, v2, now());
END;
$$
language 'plpgsql';
CREATE FUNCTION
postgres=# SELECT (func_any(1, 2)).*;
v1 | v2
----+----
2 | 3
(1 row)

postgres=# select * from tab1;
c1 | c2 | c3
----+----+----------------------------
2 | 3 | 2020-05-30 19:26:32.036924
2 | 3 | 2020-05-30 19:26:32.036924
(2 rows)

I hope, the table "tab1" should have only a single record, but we are able
to see 2 records in tab1.

it is correct, because you use composite unpacking syntax

SELECT (func_any(1, 2)).*;

means

SELECT (func_any(1, 2)).c1, (func_any(1, 2)).c2;

If you don't want double execution, you should to run your function in FROM
clause

postgres=# SELECT * FROM func_any(1, 2);
┌────┬────┐
│ v1 │ v2 │
╞════╪════╡
│ 2 │ 3 │
└────┴────┘
(1 row)

Regards

Pavel

On Fri, May 29, 2020 at 8:30 PM Pavel Stehule <pavel.stehule@gmail.com>
wrote:

pá 29. 5. 2020 v 16:45 odesílatel Prabhat Sahu <
prabhat.sahu@enterprisedb.com> napsal:

Hi All,

Please check the below scenario, with pseudotype "anyelement" for IN, OUT
parameter and the RETURN record in a function.

postgres=# create table tab1(c1 int, c2 int, c3 timestamp) ;
CREATE TABLE
postgres=# CREATE OR REPLACE FUNCTION func_any(IN anyelement, IN
anyelement, OUT v1 anyelement, OUT v2 anyelement)
RETURNS record
AS
$$
BEGIN
SELECT $1 + 1, $2 + 1 into v1, v2;
insert into tab1 values(v1, v2, now());
END;
$$
language 'plpgsql';
CREATE FUNCTION
postgres=# SELECT (func_any(1, 2)).*;
v1 | v2
----+----
2 | 3
(1 row)

postgres=# select * from tab1;
c1 | c2 | c3
----+----+----------------------------
2 | 3 | 2020-05-30 19:26:32.036924
2 | 3 | 2020-05-30 19:26:32.036924
(2 rows)

I hope, the table "tab1" should have only a single record, but we are
able to see 2 records in tab1.

it is correct, because you use composite unpacking syntax

SELECT (func_any(1, 2)).*;

means

SELECT (func_any(1, 2)).c1, (func_any(1, 2)).c2;

If you don't want double execution, you should to run your function in
FROM clause

postgres=# SELECT * FROM func_any(1, 2);
┌────┬────┐
│ v1 │ v2 │
╞════╪════╡
│ 2 │ 3 │
└────┴────┘
(1 row)

Thanks Pavel, for the help, I have verified the same, Now I am getting a
single record in tab1.
postgres=# SELECT func_any(1, 2);
func_any
----------
(2,3)
(1 row)

postgres=# select * from tab1;
c1 | c2 | c3
----+----+----------------------------
2 | 3 | 2020-05-30 20:17:59.989087
(1 row)
Thanks,
Prabhat Sahu