Hello hackers,
It turns out that in a PL/PgSQL function, you can DECLARE a variable
using the same name as one of the function parameters. This has the
effect of clobbering the parameter, for example:
CREATE OR REPLACE FUNCTION declare_clobber(foo int)
RETURNS int LANGUAGE plpgsql AS $$DECLARE foo text;BEGIN RETURN foo;END;
$$;
SELECT declare_clobber(1);
==> NULL
On the other hand, PL/PgSQL does protect against duplicate definitions
within DECLARE:
CREATE OR REPLACE FUNCTION declare_clobber(foo int)
RETURNS int LANGUAGE plpgsql AS $$DECLARE foo int; foo text;BEGIN RETURN foo;END;
$$;
==> ERROR: duplicate declaration at or near "foo"
And it also protects against using a DECLAREd name as a parameter alias:
CREATE OR REPLACE FUNCTION declare_clobber(foo int)
RETURNS int LANGUAGE plpgsql AS $$DECLARE bar int; bar ALIAS FOR $1;BEGIN RETURN bar;END;
$$;
==> ERROR: duplicate declaration at or near "bar"
I would suggest that if the user DECLAREs a variable with the same
name as a parameter, it is very evidently a programming error, and we
should raise the same "duplicate declaration" error. I haven't yet
looked at how difficult this would be to fix, but if there are no
objections I would like to attempt a patch.
Cheers,
BJ
