Using arguments with functions

[Robert Fitzpatrick]

While this function works when hard coded, the following will not when
trying the same thing with a argument. Can someone point to me what I'm
doing wrong?

CREATE OR REPLACE FUNCTION "public"."test" () RETURNS varchar AS'
DECLARE
var1 varchar;

BEGIN
var1 = chr( (ascii(''a'') + 1) );
return var1;
END;
'LANGUAGE 'plpgsql' VOLATILE RETURNS NULL ON NULL INPUT SECURITY INVOKER;

ohc=> select test();
test
------
b
(1 row)

This does not work:

CREATE OR REPLACE FUNCTION "public"."get_next" (varchar) RETURNS varchar AS'
DECLARE
var1 alias for $1;

BEGIN
var1 = chr( (ascii(var1) + 1) );
return var1;
END;
'LANGUAGE 'plpgsql' VOLATILE RETURNS NULL ON NULL INPUT SECURITY INVOKER;

ohc=> select get_next('a');
ERROR: "$1" is declared CONSTANT
CONTEXT: compile of PL/pgSQL function "get_next" near line 5

--
Robert
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[Oliver Elphick]

On Sat, 2004-07-10 at 20:50, Robert Fitzpatrick wrote:

While this function works when hard coded, the following will not when
trying the same thing with a argument. Can someone point to me what I'm
doing wrong? ....
This does not work:

CREATE OR REPLACE FUNCTION "public"."get_next" (varchar) RETURNS varchar AS'
DECLARE
var1 alias for $1;

BEGIN
var1 = chr( (ascii(var1) + 1) ); .... ERROR: "$1" is declared CONSTANT

You are trying to change the passed parameter.

Instead do

DECLARE
var1 varchar;
BEGIN
var1 = chr( (ascii($1) + 1) );

which I think should work.

--
Oliver Elphick ol**@lfix.co.uk
Isle of Wight http://www.lfix.co.uk/oliver
GPG: 1024D/A54310EA 92C8 39E7 280E 3631 3F0E 1EC0 5664 7A2F A543 10EA
========================================
"Delight thyself also in the LORD; and he shall give
thee the desires of thine heart."
Psalms 37:4
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[Tom Lane]

"Robert Fitzpatrick" <ro****@webtent.com> writes:

CREATE OR REPLACE FUNCTION "public"."get_next" (varchar) RETURNS varchar AS'
DECLARE
var1 alias for $1;
BEGIN
var1 = chr( (ascii(var1) + 1) );
...
ohc=> select get_next('a');
ERROR: "$1" is declared CONSTANT
CONTEXT: compile of PL/pgSQL function "get_next" near line 5

plpgsql does not allow you to overwrite an argument value.

regards, tom lane

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