Re: PL/pgsSQL EXECUTE USING INTO

Heikki Linnakangas <heikki(dot)linnakangas(at)enterprisedb(dot)com> writes:
> While testing the recent issue with unknown params in EXECUTE USING, I
> accidentally did this:

> EXECUTE 'SELECT ''foo'' || $1' USING 'bar' INTO t;

> The mistake I made? I put the USING and INTO clauses in wrong order,
> INTO needs to go first. We should throw an error on that, but it looks
> like the INTO clause is just silently ignored.

This is more interesting than it looks. It appears that the plpgsql
parser interprets the USING's argument expression as being
'bar' INTO t
so it generates a plplgsql expression with query
SELECT 'bar' INTO t
and the only reason that you don't get a failure is that
exec_simple_check_plan fails to notice the intoClause, so it thinks
this represents a "simple expression", which means it evaluates the
'bar' subexpression and ignores the INTO altogether. That's
certainly a bug in exec_simple_check_plan :-(

I think that accepting this order of the clauses would require some
duplication of code in the stmt_dynexecute production. It might be
worth doing anyway, because if you made this mistake then certainly
others will.

regards, tom lane