Re: Getting ERROR with FOR UPDATE/SHARE for partitioned table.

On Fri, May 22, 2020 at 5:00 PM Rajkumar Raghuwanshi <
rajkumar(dot)raghuwanshi(at)enterprisedb(dot)com> wrote:

> Hi All,
>
> I am getting ERROR when using the "FOR UPDATE" clause for the partitioned
> table. below is a reproducible test case for the same.
>
> CREATE TABLE tbl (c1 INT,c2 TEXT) PARTITION BY LIST (c1);
> CREATE TABLE tbl_null PARTITION OF tbl FOR VALUES IN (NULL);
> CREATE TABLE tbl_1 PARTITION OF tbl FOR VALUES IN (1,2,3);
>
> INSERT INTO tbl SELECT i,i FROM generate_series(1,3) i;
>
> CREATE OR REPLACE FUNCTION func(i int) RETURNS int
> AS $$
> DECLARE
> v_var tbl%ROWTYPE;
> cur CURSOR IS SELECT * FROM tbl WHERE c1< 5 FOR UPDATE;
> BEGIN
> OPEN cur;
> LOOP
> FETCH cur INTO v_var;
> EXIT WHEN NOT FOUND;
> UPDATE tbl SET c2='aa' WHERE CURRENT OF cur;
> END LOOP;
> CLOSE cur;
> RETURN 10;
> END;
> $$ LANGUAGE PLPGSQL;
>
> SELECT func(10);
>

I tried similar things on inherit partitioning as follow and that looks
fine:

DROP TABLE tbl;
CREATE TABLE tbl (c1 INT,c2 TEXT);
CREATE TABLE tbl_null(check (c1 is NULL)) INHERITS (tbl);
CREATE TABLE tbl_1 (check (c1 > 0 and c1 < 4)) INHERITS (tbl);
INSERT INTO tbl_1 VALUES(generate_series(1,3));

postgres=# SELECT func(10);
func
------
10
(1 row)

On looking further for declarative partition, I found that issue happens
only if
the partitioning pruning enabled, see this:

-- Execute on original set of test case.
postgres=# ALTER FUNCTION func SET enable_partition_pruning to off;
ALTER FUNCTION

postgres=# SELECT func(10);
func
------
10
(1 row)

I think we need some indication in execCurrentOf() to skip error if the
relation
is pruned. Something like that we already doing for inheriting
partitioning,
see following comment execCurrentOf():

/*
* This table didn't produce the cursor's current row; some other
* inheritance child of the same parent must have. Signal caller to
* do nothing on this table.
*/

Regards,
Amul