Re: PL/pgSQL bug?

Tatsuo Ishii wrote:
> It seems that sometimes uncommitted data (dirty data?) could be seen
> in PL/pgSQL function.
>
> Below is a sample script to reproduce the problem: If you execute
> "SELECT myftest(1)" concurrently, you will see the subselect in the
> SELECT INTO... will produce:
>
> ERROR: More than one tuple returned by a subselect used as an expression.
>
> This is odd, since the coulum i is a primary key, and should never has
> duplicate values.
>
> If you comment out the SELECT INTO... statement, you could see a line
> something like:
>
> NOTICE: ctid (0,5) xmin 645188 xmax 645190 cmin 2 cmax 2
>
> This is odd too, since xmax > 0 or cmax > 0 should never happen with
> visible tuples, in my understanding.
>
> I see these in 7.0.3, 7.1.2 and current.

If that's the case, it must be a general problem with SPI
that'll apply to any procedural language as well as user
defined C function using SPI.

When scans or functions are involved, PL/pgSQL uses SPI
functionality to evaluate the expression.

Jan

> --
> Tatsuo Ishii
>
> ----------------------------------------------------------------------
> DROP TABLE t1;
> CREATE TABLE t1 (i INT PRIMARY KEY);
> DROP FUNCTION myftest(INT);
> CREATE FUNCTION myftest(INT)
> RETURNS INT
> AS '
> DECLARE myid INT;
> DECLARE rec RECORD;
> key ALIAS FOR $1;
> BEGIN
> UPDATE t1 SET i = 1 WHERE i = 1;
> SELECT INTO tid,myid ctid,i FROM t1 WHERE i = (SELECT i FROM t1 WHERE i = 1);
> FOR rec IN SELECT ctid,xmin,xmax,cmin,cmax from t1 LOOP
> RAISE NOTICE ''ctid % xmin % xmax % cmin % cmax %'', rec.ctid,rec.xmin,rec.xmax,rec.cmin,rec.cmax;
> END LOOP;
> RETURN 0;
> END;
> '
> LANGUAGE 'plpgsql';
>
> ---------------------------(end of broadcast)---------------------------
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--

#======================================================================#
# It's easier to get forgiveness for being wrong than for being right. #
# Let's break this rule - forgive me. #
#================================================== JanWieck(at)Yahoo(dot)com #

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