RE: PL/pgSQL bug?

> > One way to make the results equivalent is to compute a new QuerySnapshot
> > for each SPI query.  Quite aside from the cost of doing so, I do not
> > think it makes sense, considering that the previous QuerySnapshot must
> > be restored when we return from the function.  Do we really want
> > functions to see transaction status different from what's seen outside
> > the function call?
> 
> Yes I do.

Me too. Current behavior of procedural languages seem hard to
understand for users. 

BTW, why must we restore the previous QuerySnapshot? We already break
the rule (if it's a rule). For example, COPY TO calls SetQuerySnapshot
(see tcop/utility.c). So, below produces "ERROR:  More than one tuple
returned by a subselect used as an expression":

DROP TABLE t1;
CREATE TABLE t1 (i INT PRIMARY KEY);
DROP FUNCTION myftest(INT);
CREATE FUNCTION myftest(INT)
RETURNS INT
AS ' UPDATE t1 SET i = 1 WHERE i = 1; SELECT i FROM t1 WHERE i = (SELECT i FROM t1 WHERE i = 1);'LANGUAGE 'sql';

while below does not throw an error:

DROP TABLE t1;
CREATE TABLE t1 (i INT PRIMARY KEY);
DROP FUNCTION myftest(INT);
CREATE FUNCTION myftest(INT)
RETURNS INT
AS ' UPDATE t1 SET i = 1 WHERE i = 1; COPY t1 TO ''/tmp/t1.data''; SELECT i FROM t1 WHERE i = (SELECT i FROM t1 WHERE i
=1);'LANGUAGE 'sql';